Microstructure and properties of nano-laminated Y3Si2C2 ceramics fabricated via in situ reaction by spark plasma sintering

Microstructure and properties of nano-laminated Y3Si2C2 ceramics fabricated via in situ reaction by spark plasma sintering | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Microstructure and properties of nano-laminated Y 3 Si 2 C 2 ceramics fabricated via in situ reaction by spark plasma sintering Lin-Kun Shi, Xiaobing Zhou, Jian-Qing Dai, Ke Chen, Zhengren Huang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-86504/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 14 You are reading this latest preprint version Abstract A new nano-laminated Y 3 Si 2 C 2 ceramic material, for the first time, was successfully synthesized via in situ reaction between YH 2 and SiC by spark plasma sintering. A MAX phase-like ternary layered structure of Y 3 Si 2 C 2 was observed at the atomic-scale by high resolution transmission electron microscopy. The lattice parameters calculated from both X-ray diffraction and selected area electron diffraction patterns are in good agreement with the reported theoretical results. The nano-laminated fracture of kink boundaries, delamination, and slipping was observed at the tip of the Vickers indent. The values of elastic modulus and Vickers hardness of the Y 3 Si 2 C 2 ceramics sintered at 1500 °C were 156 and 6.4 GPa, respectively. The corresponding values of thermal and electrical conductivity were 13.7 W m -1 k -1 and 6.3 × 10 5 S m -1 , respectively. Ceramics Y3Si2C2 Rare earth silicide carbides Spark plasma sintering Ternary layered structure ceramic Property Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction Rare earth silicide carbides (RE 3 Si 2 C 2 , RE = Y, La-Nd, Sm, Gd-Tm) belong to a new group of ternary layered structure materials, which were first developed by Gerdes et al. in 1998 [ 1 , 2 ]. The crystal structure of these compounds shows an orthorhombic subcell and consists of at least two different superstructures [ 2 ]. All the RE 3 Si 2 C 2 compounds were reported to have metallic conductivity and their magnetic ordering temperatures are lower than 60 K [ 1 ]. Y 3 Si 2 C 2 is one of a typical representative member of the RE 3 Si 2 C 2 group. In the Y 3 Si 2 C 2 structure, the c axis of the subcell is doubled, thus it crystallizes in the body-centered orthorhombic system with space group Imma (No. 74) [ 3 ]. On the other hand, in Y 3 Si 2 C 2 structure, Y atoms form two-dimensionally arranged infinite sheets of edge-sharing octahedra containing C 2 pairs, wherein zig-zag chains of Si atoms are interleaved [ 2 ]. Zhou et al. theoretically predicted that the bulk modulus and shear modulus of Y 3 Si 2 C 2 are 93 and 50 GPa, respectively [ 3 ]. Moreover, it was concluded that it is a soft ceramic material with good damage tolerance, due to the low shear deformation resistance and low Pugh’s ratios (G/B = 0.537; where G: shear modulus; B: bulk modulus) with low Vickers hardness of 6.9 GPa. Furthermore, the calculated volume expansion upon oxidation of Y 3 Si 2 C 2 was found to be ~ 26%, which could potentially lead to the sealing of the cracks between silicon carbide fibers (SiC f ) and SiC matrix. Therefore, Y 3 Si 2 C 2 may be a promising interphase material for SiC fiber-reinforced SiC matrix (SiC f /SiC) composite, because of the fascinating combined merits including easy cleavage, low shear deformation resistance, and volume expansions upon oxidation [ 3 ]. On the other hand, Y 3 Si 2 C 2 is inert when in contact with SiC at temperature up to 1560 °C, while a liquid phase can be formed at temperatures above 1560 °C via a ternary eutectic reaction, according to the calculated Y–Si–C ternary phase diagram [ 4 ]. Thus, Y 3 Si 2 C 2 was successfully used as sintering additive for SiC and/or SiC/Al 4 SiC 4 system [ 5 , 6 ]. The presence of a liquid phase not only effectively promotes the densification of SiC and/or SiC/Al 4 SiC 4 , but also improves the fracture toughness of ceramics by optimizing the grain boundary structure. Most importantly, Y 3 Si 2 C 2 can get decomposed into SiC and Y 2 O 3 (might act as sintering additives for SiC) at ~ 1600 °C. Therefore, Y 3 Si 2 C 2 was also successfully used as a transition phase to achieve the seamless joining of SiC ceramics [ 7 ]. The joining mechanism was identified as follows: first, the laminated Y 3 Si 2 C 2 structure was formed by the in situ reaction between Y coatings with thickness of 500 nm and SiC matrix in the joining layer at a low temperature of 1400 °C, which subsequently disappeared owing to decomposition at high temperature of 1900 °C. More recently, high-entropy RE 3 Si 2 C 2 /rare earth oxides with strong electromagnetic wave absorption capability and wide efficient absorption bandwidth were proposed and successfully synthesized, which can undeniably broaden the applications potential of RE 3 Si 2 C 2 materials [ 8 ]. Even though the Y 3 Si 2 C 2 phase has been demonstrated as a promising sintering additive and joining material for SiC-based advanced ceramics, the synthesis method and basic properties (besides electrical and magnetic properties) of Y 3 Si 2 C 2 bulk ceramics have not been investigated. The only reported technique to synthesize Y 3 Si 2 C 2 bulk ceramics is the arc-melting of cold-pressed pellets of Y, Si, and C, and subsequent annealing in evacuated silica tubes for 30 days at 900 °C [ 1 ]. This process was found to be extremely time consuming, because Y ingots were used as raw materials and the reaction temperature was as low as 900 °C. Spark plasma sintering (SPS) is an effective consolidation ceramics technology, which enables densification of ceramics at relatively low sintering temperatures and short time compared to conventional methods, since the high-density electric current can promote mass diffusion [ 9 , 10 ]. Therefore, the novel Y 3 Si 2 C 2 nano-laminated bulk ceramic material was successfully fabricated by the in situ reaction via SPS in this study. Furthermore, the phase composition, microstructure, mechanical properties, as well as electrical and thermal conductivity of Y 3 Si 2 C 2 were investigated. The measured Vickers hardness and elastic modulus were found to be in good agreement with the reported computational results. 2. Experimental 2.1. Preparation of Y 3 Si 2 C 2 YH 2 powder (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) with a purity of 99.5% and a mean particle size of 75 µm; and β-SiC powder (99.5%, Eno Material Co., Ltd., Qinhuangdao, China) with a mean particle size of 0.5 µm, were used as raw materials. For the formation of Y 3 Si 2 C 2 , the YH 2 and SiC powders were mixed in a stoichiometric ratio of 3.05:2. The in situ reaction sintering process was performed in an SPS furnace (HPD 25/1, FCT systems, Germany) under an Ar atmosphere at the temperature range of 1300–1500 °C for 30 min under a uniaxial pressure of 30 MPa. The heating and cooling rates were 50 °C min −1 . The as-obtained Y 3 Si 2 C 2 ceramics surfaces were polished using the final 1 µm diamond suspension. 2.2. Materials characterization The phase compositions of the samples were identified by X-ray diffraction (XRD, D8 Advance, Bruker AXS, Germany) with CuKα radiation (λ = 1.5406 Å) under an operating voltage of 40 kV and current of 40 mA at a step scan of 0.02° 2θ and a step time of 0.2 s. The quantitative phase composition and lattice parameters of the Y 3 Si 2 C 2 phase were analyzed by Rietveld refinement by using the TOPAS software. The surface and fracture micromorphology of the specimens were studied by scanning electron microscopy (SEM, Quanta 250 FEG, FEI, USA) system equipped with an energy dispersive spectroscopy (EDS) detector. The phase distributions and grain boundary map were characterized by electron back-scattered diffraction (EBSD) using a thermal field emission electron scanning microscope (Verios G4 uc, Thermo Scientific, USA) equipped with EBSD apparatus operating at 20 kV accelerating voltage. For the EBSD analysis, the samples were polished with the final 1 µm diamond suspension, followed by etching through an ion beam (BIB, TIC 3X, Leica, Germany) for 3 h [ 11 ]. The microstructure and phase compositions were investigated by transmission electron microscopy (TEM, Talos™ F200x, Thermo Fisher Scientific, USA) system equipped with EDS system. Thin foils for TEM observations were prepared by focused ion beam (FIB, Auriga, Carl Zeiss) technique. 2.3. Measurement of properties Apparent density (ρ) of the samples was determined by the Archimedes’ method. Elastic modulus was measured using a nanoindentation system (Hysitron PI85, Bruker) on the polished surface. Hardness of the materials was measured using a Vickers diamond indenter (HVs-1000 Digital micro Vickers Hardness Tester, Beijing Times Mountain Peak Technology Co., China) under a load of 0.5, 2, and 5 N, respectively, and a dwell time of 10 s. At least 20 indents were measured for each specimen. Electrical resistivity of samples was determined with a four-probe resistance tester (Cresbox, Napson Co., Japan). The thermal diffusivity coefficient (α) and specific heat capacity ( C p ) were measured by laser flash method using a Netzsch LFA 457 apparatus (LFA, NETZSCH-Gerätebau GmbH, Germany). The thermal conductivity (κ, W m −1 K −1 ) was calculated by using Eq. (1) [ 12 ] as follows: κ = αρC p (1) 3. Results And Discussion Figure 1 shows the XRD patterns of samples sintered at different temperatures. Y 3 Si 2 C 2 was the predominant phase for all the materials, while a trace amount of Y 2 O 3 impurity phase was also detected. Rietveld refinement technique was applied to reveal the fundamental parameters. The amount of the predominant Y 3 Si 2 C 2 phase was 88.4, 94.3, and 94.5 wt.% for the samples sintered at 1300, 1400, and 1500 °C, respectively. The corresponding amount of the minor Y 2 O 3 phase was 11.6, 5.7, and 5.5 wt.%, respectively. The lattice parameters of Y 3 Si 2 C 2 structure (a = 8.4418 Å, b = 15.6671 Å, and c = 3.863 Å) obtained from the Rietveld refinement are in good agreement with those determined by both the experimental measurements [ 2 ] and the calculation results [ 3 ], as presented in Table 1 . The values of reliability factors for the refinement processing of the above mentioned three different samples were found to be 9.1, 9.0, and 8.6%, respectively, which confirmed the reliability of the analysis and measurement approach. Table 1 The experimental lattice parameters of Y 3 Si 2 C 2 derived from Rietveld refinement and SAED patterns, and their comparison with the calculated and experimental values reported in literature. Y 3 Si 2 C 2 a (Å) b (Å) c (Å) Ref. Experimental XRD 8.4418 15.6671 3.863 This study Experimental SAED 8.439 15.719 / This study Calculated 8.426 15.634 3.846 [ 3 ] Experimental 8.4699 15.6971 3.8746 [ 2 ] The formation of Y 2 O 3 can be attributed to the presence of a trace amount of oxygen, introduced into the samples during mixing process or during sintering at high temperatures (as a trace impurity in Ar atmosphere). It is believed that YH 2 can react with SiC, thus the possible amount of residual Y decreases with increasing sintering temperature. As a result, the amount of Y 2 O 3 impurity phase decreased from 11.6 to 5.7 wt.% when the sintering temperature was increased from 1300 to 1400 °C. The amount of Y 2 O 3 at 1500 °C was only slightly lower than that detected for 1400 °C, which indicated that the reaction between YH 2 and SiC was almost complete at 1500 °C. According to the actual phase compositions of the samples, the theoretical density was calculated by using the rule of mixture [ 13 ]. The theoretical density of Y 3 Si 2 C 2 (4.547 g cm −3 ) and Y 2 O 3 (5.02 g cm −3 ) was used. The calculated theoretical density of the bulk samples was 4.596, 4.574, and 4.565 g cm −3 for the samples sintered at 1300, 1400, and 1500 °C, respectively. Thus, the relative density of as-obtained ceramics was 98.0% (1300 °C), 99.0% (1400 °C), and 99.5% (1500 °C), respectively. This clearly confirmed that high-purity and highly dense Y 3 Si 2 C 2 ceramic material was successfully obtained in a significantly shorter time compared to that reported in previous study, in which Y ingots were used [ 1 ]. Most probably, the use of Y-hydride raw powder instead of Y ingots facilitated the nucleation of Y 3 Si 2 C 2 [ 14 ]. At the same time, the use of pulsed current sintering improved the mass diffusion and promoted the solid state reaction to complete densification rapidly in a short period [ 15 ]. Figure 2 shows the microstructure of samples sintered at different temperatures, detected by EBSD. Figures 2 a–c present the diffraction pattern quality quantified using the “band contrast”, while Figs. 2 d–f show the phase distribution of Y 3 Si 2 C 2 (in red) and Y 2 O 3 (in blue). The elongated, plate-like morphology of Y 3 Si 2 C 2 was clearly identified. The phase fraction of Y 3 Si 2 C 2 measured in the observed area increased with increasing sintering temperature: 80% (1300 °C), 84% (1400 °C), and 91% (1500 °C). At the same time, the grain size distribution is shown in Figs. 2 g–i. The mean grain size of the materials increased from 3.9 µm (1300 °C) to 8.8 µm (1500 °C). The abnormal grain growth was obviously observed when the sintering temperature was increased to 1400 and 1500 °C. Figures 3 a–c show the fracture surfaces of Y 3 Si 2 C 2 sintered at 1300, 1400, and 1500 °C, respectively. The failure mode was mainly intragranular, because of low shear deformation resistance of Y 3 Si 2 C 2 [ 3 ]. Some pores and a few un-reacted SiC fine grains (determined by EDS analysis, not shown here) were observed for the sample sintered at 1300 °C (Fig. 3 a), while almost fully dense Y 3 Si 2 C 2 without any pores was observed after sintering at 1400 °C (Fig. 3 b) and 1500 °C (Fig. 3 c). TEM analysis was carried out to observe the atomic-scale microstructure of the Y 3 Si 2 C 2 sintered at 1500 °C. Figures 4 a–e exhibit a high angle annular dark field (HAADF) image and the corresponding elemental distribution of Y, C, O, and Si, respectively. The semi-quantitative EDS analysis confirmed the presence of Y 3 Si 2 C 2 and Y 2 O 3 , which correspond to the points 1 and 2 in Fig. 4 a, respectively. The EDS results are presented in Table 2 . The Y: Si ratio for the Y 3 Si 2 C 2 phase was measured to be around 1.8 by semi-quantitative EDS point analysis assuming that all oxygen was in the form of Y 2 O 3 . The atomic-scale microstructure along the [001] zone axis was confirmed by HRTEM and corresponding SAED pattern shown in Figs. 4 f and 4 g. The layered atomic stacking can be clearly seen in the HRTEM image. The lattice fringe spacing of 0.786 nm can be assigned to the (020) planes of Y 3 Si 2 C 2 , as shown in Fig. 4 g. The corresponding SAED pattern also confirmed the orthorhombic crystal structure of Y 3 Si 2 C 2 (Fig. 4 f). The lattice parameters were derived to be a = 8.439 Å and b = 15.719 Å, which are in good agreement with those determined from the XRD pattern (Table 1 ). Table 2 EDS results of the spots 1 and 2 in Fig. 3 a. Spot number Composition (at.%) Probable phase Y Si C O 1 48.3 23.2 19.7 8.8 Y 3 Si 2 C 2 2 42.2 0 4.5 53.3 Y 2 O 3 The properties of Y 3 Si 2 C 2 and some typical ternary carbides are listed in Table 3 . The elastic modulus and Vickers hardness of the materials decreased with increasing sintering temperature. This was probably caused by a decreasing amount of Y 2 O 3 in the materials with increasing temperature. The elastic modulus and Vickers hardness of Y 2 O 3 are ~ 180 and 7.6 GPa [ 19 – 21 ], respectively, which are slightly higher than the calculated values for Y 3 Si 2 C 2 [ 3 ]. Moreover, the grain size increased with increasing sintering temperature, thus the Vickers hardness also decreased with the increase in the sintering temperature according to the Hall–Petch relationship. The elastic modulus of the sample sintered at 1500 °C was close to the calculated values reported by Zhou et al. [ 3 ]. The Vickers hardness of the sample sintered at 1500 °C was 7.2 ± 0.8, 6.5 ± 0.5, and 6.4 ± 0.4 GPa for the indentation load of 0.5, 2, and 5 N, respectively. These values are in good agreement with the reported calculated value of 6.9 GPa [ 3 ]. Table 3 Density, mechanical, thermal and electrical properties of the as-obtained Y 3 Si 2 C 2 and their comparison with the reported values of typical ternary layered structural ceramics Properties Y 3 Si 2 C 2 Theoretical [ 1 , 3 ] YAl 3 C 3 [ 16 ] Ti 3 SiC 2 [ 17 ] Ti 3 AlC 2 [ 18 ] 1300 °C 1400 °C 1500 °C Theoretical density (g/cm 3 ) 4.504 4.528 4.543 4.547 3.90 4.52 4.2 Elastic modulus (GPa) 185 177 156 127 325 322 297 Vickers hardness (GPa) * 6.9 6.7 6.4 6.9 12.6 4 3.5 Thermal conductivity (W m −1 k −1 ) 16.1 15.7 13.7 N/A N/A 37 40 Electrical resistivity (10 − 6 Ω•cm) 132.2 138.2 159.1 100–270 N/A 22.7 38.7 * The value of the Vickers hardness was measured with the load of 5N. The shape of Vickers indents was irregular with the exfoliated surfaces and deformed particles, which is similar to the typical indent shape of Ti 3 SiC 2 MAX phase [ 22 ]. A typical surface morphology at the tip of a Vickers indent for the Y 3 Si 2 C 2 sample sintered at 1500 °C is shown in Figs. 5 a and 5 b. Interestingly, in the case of basal Y 3 Si 2 C 2 plane oriented parallel to the indentation load, typical nano-laminated fracture was observed, owing to the kink boundaries, delamination, and slipping (Fig. 5 a). Such behavior is commonly observed for the group of MAX phases, which belong to typical damage tolerant ceramics [ 23 ]. On the other hand, when the basal plane of Y 3 Si 2 C 2 was oriented in a direction perpendicular to the indentation load, the exfoliation and sharp steps-like fracture caused by crack deflection inside the Y 3 SiC 2 grains was observed (Fig. 5 b). The fracture energy can be consumed by virtue of crack deflection. A typical nano-laminated MAX phase-like structure of Y 3 SiC 2 is shown in Fig. 5 c, which can be easily recognized by its cleavage nature. The low Vickers hardness and typical nano-laminated fracture behavior indicated that Y 3 Si 2 C 2 belongs to the group of soft ceramics. Zhou et al. reported that the low shear deformation resistance along the (010) [101] slip system could be attributed to the weak metallic bonding between Y 2 –C [ 3 ]. Thermal conductivity of samples decreased from 16.1 to 13.7 W m −1 k −1 with the increase in the sintering temperature from 1300 to 1500 °C. This was observed despite the fact that the grain size increased with increasing sintering temperature (Fig. 2 ), which usually leads to the improved thermal conductivity due to the decreased phonon scattering by the grain boundaries. Therefore, the decreased thermal conductivity with increasing sintering temperature in this study can be attributed to the content of high thermal conductivity phase - Y 2 O 3 (27 W m −1 k −1 ) [ 24 ], which also decreased with increasing temperature. The electrical resistivity of the samples is presented in Table 3 . The corresponding electrical conductivity of samples sintered at 1300, 1400, and 1500 °C was calculated to be 7.6 × 10 5 , 7.6 × 10 5 , and 6.3 × 10 5 S m −1 , respectively. The main contribution to the electrical conductivity of Y 3 Si 2 C 2 was mainly from Y1 4de g , Y2 4dt 2g , C 2p x′ , and C 2p z′ states (x′ and z′ are inclined to the x and z axis, respectively, at about 45°) based on the analysis of the projected density of states and the decomposed distribution of electron density [ 3 ]. 4. Conclusions The high-purity highly dense Y 3 Si 2 C 2 ceramic material, for the first time, was fabricated by in situ solid state reaction between YH 2 and SiC via SPS. The as-obtained Y 3 Si 2 C 2 ceramic exhibited a nano-laminated structure, which was confirmed by HRTEM analysis. The lattice parameters were derived as a = 8.4418 Å, b = 15.6671 Å, and c = 3.863 Å by the Rietveld refinement of XRD patterns. The experimentally measured elastic modulus (156 GPa) and Vickers hardness (6.4 GPa) of the fabricated ceramics are in good agreement with the reported theoretically calculated values. Typical nano-laminated fracture behavior was observed at the tip of Vickers indents, which indicated that Y 3 Si 2 C 2 belongs to the group of soft ceramics. The thermal and electrical conductivity of the sample sintered at 1500 °C was 13.7 W m −1 k −1 and 6.3 × 10 5 S m −1 , respectively. The proposed synthesized strategy could potentially be used to fabricate other RE 3 Si 2 C 2 phases. Declarations Acknowledgments We would like to recognize the support from the Ningbo 3315 Innovative Teams Program, China (Grant NO. 2019A-14-C). This study was supported by the National Natural Science Foundation of China (Grant No. 11975296 and 51811540402). References [1] Gerdes MH, Witte AM, Jeitschko W, et al. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-86504","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":3036765,"identity":"98105d62-222e-456c-9094-ed6682d3e6a1","order_by":0,"name":"Lin-Kun Shi","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Lin-Kun","middleName":"","lastName":"Shi","suffix":""},{"id":3036766,"identity":"50bc6065-6986-461a-ade1-7509317ede34","order_by":1,"name":"Xiaobing Zhou","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxElEQVRIiWNgGAWjYDACCSBmbLBhYCNVSxpQCzNpWg4DSWK1yM9uPibNu+N8Hp/Y+YMPGGrsGPhnN+DXwjjnWJrkzDO3i9mkk5kNGI4lM0jcOYBfC7NEjpnEx7bbiW3SyWwSDGwHGAwkEvBrYQNpSWw7B9LC/oPhHxFaeCC2HADbwsDYRoQWCYm0ZMuZZ5JBWowlEvuSeSRuENAiPyP54G3eHXaJ82cnPvzw4ZudHP8MAlpQAVAxDynqR8EoGAWjYBTgAAAvUzp1pv1mwQAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0001-8258-3729","institution":"Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Xiaobing","middleName":"","lastName":"Zhou","suffix":""},{"id":3036767,"identity":"c3f16dbb-ae99-4825-b563-a3271eb702a8","order_by":2,"name":"Jian-Qing Dai","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jian-Qing","middleName":"","lastName":"Dai","suffix":""},{"id":3036768,"identity":"c5b58d76-d6da-45e0-a8d2-7bc641cba170","order_by":3,"name":"Ke Chen","email":"","orcid":"","institution":"Ningbo Institute of Materials Technology and Engineering CAS","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Ke","middleName":"","lastName":"Chen","suffix":""},{"id":3036769,"identity":"9d30ff77-7e45-4497-b63d-f9207124c4e8","order_by":4,"name":"Zhengren Huang","email":"","orcid":"","institution":"Ningbo Institute of Materials Technology and Engineering CAS","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhengren","middleName":"","lastName":"Huang","suffix":""},{"id":3036770,"identity":"03723ea4-3c57-4795-b92b-d57d5e7620f3","order_by":5,"name":"Qing Huang","email":"","orcid":"","institution":"Ningbo Institute of Materials Technology and Engineering CAS","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Qing","middleName":"","lastName":"Huang","suffix":""}],"badges":[],"createdAt":"2020-10-01 14:49:01","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-86504/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-86504/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":2865494,"identity":"121cc42a-ec56-41eb-914d-cf035f9adece","added_by":"auto","created_at":"2020-10-08 18:08:53","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":54001,"visible":true,"origin":"","legend":"XRD patterns of Y3Si2C2 sintered at various temperatures by reactive SPS.","description":"","filename":"OnlineFig.1.Png","url":"https://assets-eu.researchsquare.com/files/rs-86504/v1/af25ed8cb98431d82b4bbc55.Png"},{"id":2865495,"identity":"04c821bb-f453-4ce9-bf9c-1eb66bb59198","added_by":"auto","created_at":"2020-10-08 18:08:53","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":170684,"visible":true,"origin":"","legend":"Microstructure of samples fabricated at various temperatures observed by EBSD: micrograph in band contrast (a) 1300 °C; (b) 1400 °C; (c) 1500 °C; phase distribution: Y3Si2C2 in red and Y2O3 in blue (d) 1300 °C; (e) 1400 °C; (f) 1500 °C; grain size distribution (g) 1300 °C; (h) 1400 °C; (i) 1500 °C.","description":"","filename":"OnlineFig.2.Png","url":"https://assets-eu.researchsquare.com/files/rs-86504/v1/1b606607b142976901437bca.Png"},{"id":2865496,"identity":"b35ec631-8e49-4056-a5bd-dfcaa44779db","added_by":"auto","created_at":"2020-10-08 18:08:54","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":628428,"visible":true,"origin":"","legend":"SEM images of the fractured surfaces of Y3Si2C2 sintered by reactive SPS at (a) 1300 °C; (b) 1400 °C; (c) 1500 °C.","description":"","filename":"OnlineFig.3.Png","url":"https://assets-eu.researchsquare.com/files/rs-86504/v1/00a019c37eb94dc1b7667d98.Png"},{"id":2865497,"identity":"2a752cd2-749f-4527-ae37-daa1e34562d4","added_by":"auto","created_at":"2020-10-08 18:08:54","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":535620,"visible":true,"origin":"","legend":"TEM image of Y3Si2C2 ceramics sintered at 1500 °C: (a) HAADF image and elemental distribution of (b) Y; (c) C; (d) O; (e) Si; (f) SAED pattern for the yellow area in (a); (g) HRTEM image of Y3Si2C2, the insert includes structure models showing the positions of Y, Si, and C.","description":"","filename":"OnlineFig.4.Png","url":"https://assets-eu.researchsquare.com/files/rs-86504/v1/787a0b1cfde82af0c2812f7d.Png"},{"id":2865498,"identity":"00937300-9b72-4ad8-88d4-88f36fa7fc64","added_by":"auto","created_at":"2020-10-08 18:08:54","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":104012,"visible":true,"origin":"","legend":"Surface morphology of sample sintered at 1500 °C after Vickers indentation test: (a) basal Y3Si2C2 plane oriented parallel to the load with the presence of kinks, delamination, and slipping; (b) basal Y3Si2C2 plane oriented perpendicular to the load showing the exfoliation; (c) high magnification SEM image showing the nano-laminated structure of Y3Si2C2.","description":"","filename":"OnlineFig.5.Png","url":"https://assets-eu.researchsquare.com/files/rs-86504/v1/f475301d02e7003e44606003.Png"},{"id":15669221,"identity":"e5245ee4-749d-4db0-9980-9748526d5144","added_by":"auto","created_at":"2021-11-18 13:52:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2771131,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-86504/v1/270a9a78-1e74-4f36-8ef0-366b0efbd4a1.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eMicrostructure and properties of nano-laminated Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2 \u003c/sub\u003eceramics fabricated via \u003cem\u003ein situ \u003c/em\u003ereaction by spark plasma sintering\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eRare earth silicide carbides (RE\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e, RE\u0026thinsp;=\u0026thinsp;Y, La-Nd, Sm, Gd-Tm) belong to a new group of ternary layered structure materials, which were first developed by Gerdes et al. in 1998 [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e]. The crystal structure of these compounds shows an orthorhombic subcell and consists of at least two different superstructures [\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e]. All the RE\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e compounds were reported to have metallic conductivity and their magnetic ordering temperatures are lower than 60\u0026nbsp;K [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e]. Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e is one of a typical representative member of the RE\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e group. In the Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e structure, the \u003cem\u003ec\u003c/em\u003e axis of the subcell is doubled, thus it crystallizes in the body-centered orthorhombic system with space group Imma (No. 74) [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]. On the other hand, in Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e structure, Y atoms form two-dimensionally arranged infinite sheets of edge-sharing octahedra containing C\u003csub\u003e2\u003c/sub\u003e pairs, wherein zig-zag chains of Si atoms are interleaved [\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eZhou et al. theoretically predicted that the bulk modulus and shear modulus of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e are 93 and 50 GPa, respectively [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]. Moreover, it was concluded that it is a soft ceramic material with good damage tolerance, due to the low shear deformation resistance and low Pugh\u0026rsquo;s ratios (G/B\u0026thinsp;=\u0026thinsp;0.537; where G: shear modulus; B: bulk modulus) with low Vickers hardness of 6.9 GPa. Furthermore, the calculated volume expansion upon oxidation of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e was found to be ~\u0026thinsp;26%, which could potentially lead to the sealing of the cracks between silicon carbide fibers (SiC\u003csub\u003ef\u003c/sub\u003e) and SiC matrix. Therefore, Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e may be a promising interphase material for SiC fiber-reinforced SiC matrix (SiC\u003csub\u003ef\u003c/sub\u003e/SiC) composite, because of the fascinating combined merits including easy cleavage, low shear deformation resistance, and volume expansions upon oxidation [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eOn the other hand, Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e is inert when in contact with SiC at temperature up to 1560\u0026nbsp;\u0026deg;C, while a liquid phase can be formed at temperatures above 1560\u0026nbsp;\u0026deg;C via a ternary eutectic reaction, according to the calculated Y\u0026ndash;Si\u0026ndash;C ternary phase diagram [\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e]. Thus, Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e was successfully used as sintering additive for SiC and/or SiC/Al\u003csub\u003e4\u003c/sub\u003eSiC\u003csub\u003e4\u003c/sub\u003e system [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e]. The presence of a liquid phase not only effectively promotes the densification of SiC and/or SiC/Al\u003csub\u003e4\u003c/sub\u003eSiC\u003csub\u003e4\u003c/sub\u003e, but also improves the fracture toughness of ceramics by optimizing the grain boundary structure. Most importantly, Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e can get decomposed into SiC and Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (might act as sintering additives for SiC) at ~\u0026thinsp;1600\u0026nbsp;\u0026deg;C. Therefore, Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e was also successfully used as a transition phase to achieve the seamless joining of SiC ceramics [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]. The joining mechanism was identified as follows: first, the laminated Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e structure was formed by the \u003cem\u003ein situ\u003c/em\u003e reaction between Y coatings with thickness of 500\u0026nbsp;nm and SiC matrix in the joining layer at a low temperature of 1400\u0026nbsp;\u0026deg;C, which subsequently disappeared owing to decomposition at high temperature of 1900\u0026nbsp;\u0026deg;C. More recently, high-entropy RE\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e/rare earth oxides with strong electromagnetic wave absorption capability and wide efficient absorption bandwidth were proposed and successfully synthesized, which can undeniably broaden the applications potential of RE\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e materials [\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eEven though the Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e phase has been demonstrated as a promising sintering additive and joining material for SiC-based advanced ceramics, the synthesis method and basic properties (besides electrical and magnetic properties) of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e bulk ceramics have not been investigated. The only reported technique to synthesize Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e bulk ceramics is the arc-melting of cold-pressed pellets of Y, Si, and C, and subsequent annealing in evacuated silica tubes for 30 days at 900\u0026nbsp;\u0026deg;C [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e]. This process was found to be extremely time consuming, because Y ingots were used as raw materials and the reaction temperature was as low as 900\u0026nbsp;\u0026deg;C. Spark plasma sintering (SPS) is an effective consolidation ceramics technology, which enables densification of ceramics at relatively low sintering temperatures and short time compared to conventional methods, since the high-density electric current can promote mass diffusion [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eTherefore, the novel Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e nano-laminated bulk ceramic material was successfully fabricated by the \u003cem\u003ein situ\u003c/em\u003e reaction via SPS in this study. Furthermore, the phase composition, microstructure, mechanical properties, as well as electrical and thermal conductivity of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e were investigated. The measured Vickers hardness and elastic modulus were found to be in good agreement with the reported computational results.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n\u003cp\u003e\u003cstrong\u003e2.1. Preparation of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eYH\u003csub\u003e2\u003c/sub\u003e powder (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) with a purity of 99.5% and a mean particle size of 75\u0026nbsp;\u0026micro;m; and \u0026beta;-SiC powder (99.5%, Eno Material Co., Ltd., Qinhuangdao, China) with a mean particle size of 0.5\u0026nbsp;\u0026micro;m, were used as raw materials. For the formation of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e, the YH\u003csub\u003e2\u003c/sub\u003e and SiC powders were mixed in a stoichiometric ratio of 3.05:2. The \u003cem\u003ein situ\u003c/em\u003e reaction sintering process was performed in an SPS furnace (HPD 25/1, FCT systems, Germany) under an Ar atmosphere at the temperature range of 1300\u0026ndash;1500\u0026nbsp;\u0026deg;C for 30\u0026nbsp;min under a uniaxial pressure of 30\u0026nbsp;MPa. The heating and cooling rates were 50\u0026nbsp;\u0026deg;C min\u003csup\u003e\u0026minus;1\u003c/sup\u003e. The as-obtained Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e ceramics surfaces were polished using the final 1\u0026nbsp;\u0026micro;m diamond suspension.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n\u003cp\u003e\u003cstrong\u003e2.2. Materials characterization\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe phase compositions of the samples were identified by X-ray diffraction (XRD, D8 Advance, Bruker AXS, Germany) with CuK\u0026alpha; radiation (\u0026lambda;\u0026thinsp;=\u0026thinsp;1.5406\u0026nbsp;\u0026Aring;) under an operating voltage of 40\u0026nbsp;kV and current of 40\u0026nbsp;mA at a step scan of 0.02\u0026deg; 2\u0026theta; and a step time of 0.2\u0026nbsp;s. The quantitative phase composition and lattice parameters of the Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e phase were analyzed by Rietveld refinement by using the TOPAS software.\u003c/p\u003e\n\u003cp\u003eThe surface and fracture micromorphology of the specimens were studied by scanning electron microscopy (SEM, Quanta 250 FEG, FEI, USA) system equipped with an energy dispersive spectroscopy (EDS) detector. The phase distributions and grain boundary map were characterized by electron back-scattered diffraction (EBSD) using a thermal field emission electron scanning microscope (Verios G4 uc, Thermo Scientific, USA) equipped with EBSD apparatus operating at 20\u0026nbsp;kV accelerating voltage. For the EBSD analysis, the samples were polished with the final 1\u0026nbsp;\u0026micro;m diamond suspension, followed by etching through an ion beam (BIB, TIC 3X, Leica, Germany) for 3\u0026nbsp;h [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]. The microstructure and phase compositions were investigated by transmission electron microscopy (TEM, Talos\u0026trade; F200x, Thermo Fisher Scientific, USA) system equipped with EDS system. Thin foils for TEM observations were prepared by focused ion beam (FIB, Auriga, Carl Zeiss) technique.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.3. Measurement of properties\u003c/strong\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n\u003cp\u003eApparent density (\u0026rho;) of the samples was determined by the Archimedes\u0026rsquo; method. Elastic modulus was measured using a nanoindentation system (Hysitron PI85, Bruker) on the polished surface. Hardness of the materials was measured using a Vickers diamond indenter (HVs-1000 Digital micro Vickers Hardness Tester, Beijing Times Mountain Peak Technology Co., China) under a load of 0.5, 2, and 5\u0026nbsp;N, respectively, and a dwell time of 10\u0026nbsp;s. At least 20 indents were measured for each specimen. Electrical resistivity of samples was determined with a four-probe resistance tester (Cresbox, Napson Co., Japan). The thermal diffusivity coefficient (\u0026alpha;) and specific heat capacity (\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ep\u003c/em\u003e\u003c/sub\u003e) were measured by laser flash method using a Netzsch LFA 457 apparatus (LFA, NETZSCH-Ger\u0026auml;tebau GmbH, Germany). The thermal conductivity (\u0026kappa;, W m\u003csup\u003e\u0026minus;1\u003c/sup\u003e K\u003csup\u003e\u0026minus;1\u003c/sup\u003e) was calculated by using Eq.\u0026nbsp;(1) [\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e] as follows:\u003c/p\u003e\n\u003cp\u003e\u0026kappa;\u0026thinsp;=\u0026thinsp;\u0026alpha;\u0026rho;C\u003csub\u003ep\u003c/sub\u003e (1)\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results And Discussion","content":"\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e shows the XRD patterns of samples sintered at different temperatures. Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e was the predominant phase for all the materials, while a trace amount of Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e impurity phase was also detected. Rietveld refinement technique was applied to reveal the fundamental parameters. The amount of the predominant Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e phase was 88.4, 94.3, and 94.5 wt.% for the samples sintered at 1300, 1400, and 1500\u0026nbsp;\u0026deg;C, respectively. The corresponding amount of the minor Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e phase was 11.6, 5.7, and 5.5 wt.%, respectively. The lattice parameters of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e structure (a\u0026thinsp;=\u0026thinsp;8.4418\u0026nbsp;\u0026Aring;, b\u0026thinsp;=\u0026thinsp;15.6671\u0026nbsp;\u0026Aring;, and c\u0026thinsp;=\u0026thinsp;3.863\u0026nbsp;\u0026Aring;) obtained from the Rietveld refinement are in good agreement with those determined by both the experimental measurements [\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e] and the calculation results [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e], as presented in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The values of reliability factors for the refinement processing of the above mentioned three different samples were found to be 9.1, 9.0, and 8.6%, respectively, which confirmed the reliability of the analysis and measurement approach.\u0026nbsp;\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eThe experimental lattice parameters of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e derived from Rietveld refinement and SAED patterns, and their comparison with the calculated and experimental values reported in literature.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eY\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003ea (\u0026Aring;)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eb (\u0026Aring;)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003ec (\u0026Aring;)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eRef.\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eExperimental XRD\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.4418\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e15.6671\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.863\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eThis study\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eExperimental SAED\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.439\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e15.719\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e/\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eThis study\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCalculated\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.426\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e15.634\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.846\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e[\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eExperimental\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.4699\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e15.6971\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.8746\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e[\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/div\u003e\n\u003cp\u003eThe formation of Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e can be attributed to the presence of a trace amount of oxygen, introduced into the samples during mixing process or during sintering at high temperatures (as a trace impurity in Ar atmosphere). It is believed that YH\u003csub\u003e2\u003c/sub\u003e can react with SiC, thus the possible amount of residual Y decreases with increasing sintering temperature. As a result, the amount of Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e impurity phase decreased from 11.6 to 5.7 wt.% when the sintering temperature was increased from 1300 to 1400\u0026nbsp;\u0026deg;C. The amount of Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e at 1500\u0026nbsp;\u0026deg;C was only slightly lower than that detected for 1400\u0026nbsp;\u0026deg;C, which indicated that the reaction between YH\u003csub\u003e2\u003c/sub\u003e and SiC was almost complete at 1500\u0026nbsp;\u0026deg;C.\u003c/p\u003e\n\u003cp\u003eAccording to the actual phase compositions of the samples, the theoretical density was calculated by using the rule of mixture [\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e]. The theoretical density of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e (4.547\u0026nbsp;g cm\u003csup\u003e\u0026minus;3\u003c/sup\u003e) and Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (5.02\u0026nbsp;g cm\u003csup\u003e\u0026minus;3\u003c/sup\u003e) was used. The calculated theoretical density of the bulk samples was 4.596, 4.574, and 4.565\u0026nbsp;g cm\u003csup\u003e\u0026minus;3\u003c/sup\u003e for the samples sintered at 1300, 1400, and 1500\u0026nbsp;\u0026deg;C, respectively. Thus, the relative density of as-obtained ceramics was 98.0% (1300\u0026nbsp;\u0026deg;C), 99.0% (1400\u0026nbsp;\u0026deg;C), and 99.5% (1500\u0026nbsp;\u0026deg;C), respectively. This clearly confirmed that high-purity and highly dense Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e ceramic material was successfully obtained in a significantly shorter time compared to that reported in previous study, in which Y ingots were used [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e]. Most probably, the use of Y-hydride raw powder instead of Y ingots facilitated the nucleation of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e [\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]. At the same time, the use of pulsed current sintering improved the mass diffusion and promoted the solid state reaction to complete densification rapidly in a short period [\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e shows the microstructure of samples sintered at different temperatures, detected by EBSD. Figures\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea\u0026ndash;c present the diffraction pattern quality quantified using the \u0026ldquo;band contrast\u0026rdquo;, while Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ed\u0026ndash;f show the phase distribution of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e (in red) and Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (in blue). The elongated, plate-like morphology of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e was clearly identified. The phase fraction of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e measured in the observed area increased with increasing sintering temperature: 80% (1300\u0026nbsp;\u0026deg;C), 84% (1400\u0026nbsp;\u0026deg;C), and 91% (1500\u0026nbsp;\u0026deg;C). At the same time, the grain size distribution is shown in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eg\u0026ndash;i. The mean grain size of the materials increased from 3.9\u0026nbsp;\u0026micro;m (1300\u0026nbsp;\u0026deg;C) to 8.8\u0026nbsp;\u0026micro;m (1500\u0026nbsp;\u0026deg;C). The abnormal grain growth was obviously observed when the sintering temperature was increased to 1400 and 1500\u0026nbsp;\u0026deg;C.\u003c/p\u003e\n\u003cp\u003eFigures\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea\u0026ndash;c show the fracture surfaces of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e sintered at 1300, 1400, and 1500\u0026nbsp;\u0026deg;C, respectively. The failure mode was mainly intragranular, because of low shear deformation resistance of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]. Some pores and a few un-reacted SiC fine grains (determined by EDS analysis, not shown here) were observed for the sample sintered at 1300\u0026nbsp;\u0026deg;C (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea), while almost fully dense Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e without any pores was observed after sintering at 1400\u0026nbsp;\u0026deg;C (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb) and 1500\u0026nbsp;\u0026deg;C (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ec).\u003c/p\u003e\n\u003cp\u003eTEM analysis was carried out to observe the atomic-scale microstructure of the Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e sintered at 1500\u0026nbsp;\u0026deg;C. Figures\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea\u0026ndash;e exhibit a high angle annular dark field (HAADF) image and the corresponding elemental distribution of Y, C, O, and Si, respectively. The semi-quantitative EDS analysis confirmed the presence of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e and Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, which correspond to the points 1 and 2 in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea, respectively. The EDS results are presented in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e. The Y: Si ratio for the Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e phase was measured to be around 1.8 by semi-quantitative EDS point analysis assuming that all oxygen was in the form of Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. The atomic-scale microstructure along the [001] zone axis was confirmed by HRTEM and corresponding SAED pattern shown in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ef and \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e\u0026nbsp;g. The layered atomic stacking can be clearly seen in the HRTEM image. The lattice fringe spacing of 0.786\u0026nbsp;nm can be assigned to the (020) planes of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eg. The corresponding SAED pattern also confirmed the orthorhombic crystal structure of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ef). The lattice parameters were derived to be \u003cem\u003ea\u003c/em\u003e\u0026thinsp;=\u0026thinsp;8.439\u0026nbsp;\u0026Aring; and \u003cem\u003eb\u003c/em\u003e\u0026thinsp;=\u0026thinsp;15.719\u0026nbsp;\u0026Aring;, which are in good agreement with those determined from the XRD pattern (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u0026nbsp;\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eEDS results of the spots 1 and 2 in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eSpot\u003c/p\u003e\n\u003cp\u003enumber\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eComposition (at.%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eProbable\u003c/p\u003e\n\u003cp\u003ephase\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eY\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSi\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eC\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eO\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e48.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e19.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.8\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eY\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e42.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e4.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e53.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eY\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/div\u003e\n\u003cp\u003eThe properties of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e and some typical ternary carbides are listed in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. The elastic modulus and Vickers hardness of the materials decreased with increasing sintering temperature. This was probably caused by a decreasing amount of Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in the materials with increasing temperature. The elastic modulus and Vickers hardness of Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e are ~\u0026thinsp;180 and 7.6 GPa [\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e], respectively, which are slightly higher than the calculated values for Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]. Moreover, the grain size increased with increasing sintering temperature, thus the Vickers hardness also decreased with the increase in the sintering temperature according to the Hall\u0026ndash;Petch relationship. The elastic modulus of the sample sintered at 1500\u0026nbsp;\u0026deg;C was close to the calculated values reported by Zhou et al. [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]. The Vickers hardness of the sample sintered at 1500\u0026nbsp;\u0026deg;C was 7.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8, 6.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5, and 6.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4 GPa for the indentation load of 0.5, 2, and 5\u0026nbsp;N, respectively. These values are in good agreement with the reported calculated value of 6.9 GPa [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eDensity, mechanical, thermal and electrical properties of the as-obtained Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e and their comparison with the reported values of typical ternary layered structural ceramics\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eProperties\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"3\" align=\"left\"\u003e\n\u003cp\u003eY\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eTheoretical [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eYAl\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e3\u003c/sub\u003e [\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eTi\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eTi\u003csub\u003e3\u003c/sub\u003eAlC\u003csub\u003e2\u003c/sub\u003e [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e1300\u0026nbsp;\u0026deg;C\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e1400\u0026nbsp;\u0026deg;C\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e1500\u0026nbsp;\u0026deg;C\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTheoretical density (g/cm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.504\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.528\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.543\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.547\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.90\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.52\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.2\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eElastic modulus\u003c/p\u003e\n\u003cp\u003e(GPa)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e185\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e177\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e156\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e127\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e325\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e322\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e297\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eVickers hardness\u003c/p\u003e\n\u003cp\u003e(GPa)\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e12.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.5\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eThermal conductivity\u003c/p\u003e\n\u003cp\u003e(W m\u003csup\u003e\u0026minus;1\u003c/sup\u003e k\u003csup\u003e\u0026minus;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e16.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e15.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e13.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eN/A\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eN/A\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e37\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e40\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eElectrical resistivity\u003c/p\u003e\n\u003cp\u003e(10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e Ω\u0026bull;cm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e132.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e138.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e159.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100\u0026ndash;270\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eN/A\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e22.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e38.7\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003ctfoot\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e* The value of the Vickers hardness was measured with the load of 5N.\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tfoot\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/div\u003e\n\u003cp\u003eThe shape of Vickers indents was irregular with the exfoliated surfaces and deformed particles, which is similar to the typical indent shape of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e MAX phase [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]. A typical surface morphology at the tip of a Vickers indent for the Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e sample sintered at 1500\u0026nbsp;\u0026deg;C is shown in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea and \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb. Interestingly, in the case of basal Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e plane oriented parallel to the indentation load, typical nano-laminated fracture was observed, owing to the kink boundaries, delamination, and slipping (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea). Such behavior is commonly observed for the group of MAX phases, which belong to typical damage tolerant ceramics [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e]. On the other hand, when the basal plane of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e was oriented in a direction perpendicular to the indentation load, the exfoliation and sharp steps-like fracture caused by crack deflection inside the Y\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e grains was observed (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb). The fracture energy can be consumed by virtue of crack deflection. A typical nano-laminated MAX phase-like structure of Y\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e is shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ec, which can be easily recognized by its cleavage nature. The low Vickers hardness and typical nano-laminated fracture behavior indicated that Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e belongs to the group of soft ceramics. Zhou et al. reported that the low shear deformation resistance along the (010) [101] slip system could be attributed to the weak metallic bonding between Y\u003csub\u003e2\u003c/sub\u003e\u0026ndash;C [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThermal conductivity of samples decreased from 16.1 to 13.7\u0026nbsp;W m\u003csup\u003e\u0026minus;1\u003c/sup\u003e k\u003csup\u003e\u0026minus;1\u003c/sup\u003e with the increase in the sintering temperature from 1300 to 1500\u0026nbsp;\u0026deg;C. This was observed despite the fact that the grain size increased with increasing sintering temperature (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e), which usually leads to the improved thermal conductivity due to the decreased phonon scattering by the grain boundaries. Therefore, the decreased thermal conductivity with increasing sintering temperature in this study can be attributed to the content of high thermal conductivity phase - Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (27\u0026nbsp;W m\u003csup\u003e\u0026minus;1\u003c/sup\u003e k\u003csup\u003e\u0026minus;1\u003c/sup\u003e) [\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e], which also decreased with increasing temperature.\u003c/p\u003e\n\u003cp\u003eThe electrical resistivity of the samples is presented in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. The corresponding electrical conductivity of samples sintered at 1300, 1400, and 1500\u0026nbsp;\u0026deg;C was calculated to be 7.6\u0026thinsp;\u0026times;\u0026thinsp;10\u003csup\u003e5\u003c/sup\u003e, 7.6\u0026thinsp;\u0026times;\u0026thinsp;10\u003csup\u003e5\u003c/sup\u003e, and 6.3\u0026thinsp;\u0026times;\u0026thinsp;10\u003csup\u003e5\u003c/sup\u003e S m\u003csup\u003e\u0026minus;1\u003c/sup\u003e, respectively. The main contribution to the electrical conductivity of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e was mainly from Y1 4de\u003csub\u003eg\u003c/sub\u003e, Y2 4dt\u003csub\u003e2g\u003c/sub\u003e, C 2p\u003csub\u003ex\u0026prime;\u003c/sub\u003e, and C 2p\u003csub\u003ez\u0026prime;\u003c/sub\u003e states (x\u0026prime; and z\u0026prime; are inclined to the x and z axis, respectively, at about 45\u0026deg;) based on the analysis of the projected density of states and the decomposed distribution of electron density [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e"},{"header":"4. Conclusions","content":" \u003cp\u003eThe high-purity highly dense Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e ceramic material, for the first time, was fabricated by \u003cem\u003ein situ\u003c/em\u003e solid state reaction between YH\u003csub\u003e2\u003c/sub\u003e and SiC via SPS. The as-obtained Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e ceramic exhibited a nano-laminated structure, which was confirmed by HRTEM analysis. The lattice parameters were derived as \u003cem\u003ea\u003c/em\u003e\u0026thinsp;=\u0026thinsp;8.4418\u0026nbsp;\u0026Aring;, \u003cem\u003eb\u003c/em\u003e\u0026thinsp;=\u0026thinsp;15.6671\u0026nbsp;\u0026Aring;, and \u003cem\u003ec\u003c/em\u003e\u0026thinsp;=\u0026thinsp;3.863\u0026nbsp;\u0026Aring; by the Rietveld refinement of XRD patterns. The experimentally measured elastic modulus (156 GPa) and Vickers hardness (6.4 GPa) of the fabricated ceramics are in good agreement with the reported theoretically calculated values. Typical nano-laminated fracture behavior was observed at the tip of Vickers indents, which indicated that Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e belongs to the group of soft ceramics. The thermal and electrical conductivity of the sample sintered at 1500\u0026nbsp;\u0026deg;C was 13.7\u0026nbsp;W m\u003csup\u003e\u0026minus;1\u003c/sup\u003e k\u003csup\u003e\u0026minus;1\u003c/sup\u003e and 6.3\u0026thinsp;\u0026times;\u0026thinsp;10\u003csup\u003e5\u003c/sup\u003e S m\u003csup\u003e\u0026minus;1\u003c/sup\u003e, respectively. The proposed synthesized strategy could potentially be used to fabricate other RE\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e phases.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to recognize the support from the Ningbo 3315 Innovative Teams Program, China (Grant NO. 2019A-14-C). This study was supported by the National Natural Science Foundation of China (Grant No. 11975296 and 51811540402).\u003c/p\u003e"},{"header":"References","content":"\u003cp\u003e[1] Gerdes MH, Witte AM, Jeitschko W, et al. 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Structural and optical properties of Tm:Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e transparent ceramic with La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, ZrO\u003csub\u003e2\u003c/sub\u003e as composite sintering aid. \u003cem\u003eJ\u003c/em\u003e \u003cem\u003eEur\u003c/em\u003e \u003cem\u003eCeram\u003c/em\u003e \u003cem\u003eSoc\u003c/em\u003e 2012, 32: 381-388.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-advanced-ceramics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jace","sideBox":"Learn more about [Journal of Advanced Ceramics](http://link.springer.com/journal/40145)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/jace/default.aspx","title":"Journal of Advanced Ceramics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Y3Si2C2, Rare earth silicide carbides, Spark plasma sintering, Ternary layered structure ceramic, Property","lastPublishedDoi":"10.21203/rs.3.rs-86504/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-86504/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\tA new nano-laminated Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e ceramic material, for the first time, was successfully synthesized via \u003cem\u003ein situ\u003c/em\u003e reaction between YH\u003csub\u003e2\u003c/sub\u003e and SiC by spark plasma sintering. A MAX phase-like ternary layered structure of Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e was observed at the atomic-scale by high resolution transmission electron microscopy. The lattice parameters calculated from both X-ray diffraction and selected area electron diffraction patterns are in good agreement with the reported theoretical results. The nano-laminated fracture of kink boundaries, delamination, and slipping was observed at the tip of the Vickers indent. The values of elastic modulus and Vickers hardness of the Y\u003csub\u003e3\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e ceramics sintered at 1500 °C were 156 and 6.4 GPa, respectively. The corresponding values of thermal and electrical conductivity were 13.7 W m\u003csup\u003e-1\u003c/sup\u003e k\u003csup\u003e-1\u003c/sup\u003e and 6.3 × 10\u003csup\u003e5\u003c/sup\u003e S m\u003csup\u003e-1\u003c/sup\u003e, respectively.\u0026nbsp;\u003c/p\u003e","manuscriptTitle":"Microstructure and properties of nano-laminated Y3Si2C2 ceramics fabricated via in situ reaction by spark plasma sintering","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2020-10-08 18:08:52","doi":"10.21203/rs.3.rs-86504/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revisions","date":"2020-11-17T00:00:00+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2020-11-16T00:00:00+00:00","index":4,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"editorInvitedReview","content":"","date":"2020-11-15T00:00:00+00:00","index":3,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"reviewerAgreed","content":"","date":"2020-10-31T01:00:00+00:00","index":4,"fulltext":""},{"type":"reviewerAgreed","content":"","date":"2020-10-31T00:00:00+00:00","index":3,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2020-10-16T12:00:00+00:00","index":1,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"editorInvitedReview","content":"","date":"2020-10-16T12:00:00+00:00","index":2,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"reviewerAgreed","content":"","date":"2020-10-03T12:00:00+00:00","index":1,"fulltext":""},{"type":"reviewerAgreed","content":"","date":"2020-10-03T12:00:00+00:00","index":2,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2020-10-02T12:00:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"","date":"2020-10-01T12:00:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2020-10-01T12:00:00+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2020-09-30T12:00:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2020-09-30T12:00:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-advanced-ceramics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jace","sideBox":"Learn more about [Journal of Advanced Ceramics](http://link.springer.com/journal/40145)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/jace/default.aspx","title":"Journal of Advanced Ceramics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"02ae03de-38dc-4b55-87e9-cc1b877e5c24","owner":[],"postedDate":"October 8th, 2020","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":694035,"name":"Ceramics"}],"tags":[],"updatedAt":"2021-05-31T14:17:19+00:00","versionOfRecord":[],"versionCreatedAt":"2020-10-08 18:08:52","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-86504","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-86504","identity":"rs-86504","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}