Microstructural analysis of polyimide-based nanocomposite with BaTiO 3 :Eu nanoceramics using high and low positron annihilation techniques

Microstructural analysis of polyimide-based nanocomposite with BaTiO 3 :Eu nanoceramics using high and low positron annihilation techniques | 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 Microstructural analysis of polyimide-based nanocomposite with BaTiO 3 :Eu nanoceramics using high and low positron annihilation techniques Mahdi Ghasemifard, Misagh Ghamari, Cumali Tav, Ugur Yahsi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6859860/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study investigates the microstructural properties of polyimide-based nanocomposites filled with Ba₀.₉₅Eu₀.₀₅TiO₃ (BETO) nanoceramics using advanced positron annihilation in fast and slow modes. The addition of BETO nanoceramics introduces unique free volume characteristics and defect states, which are critical to increasing the optical and structural performance of the nanocomposites. It explores the relationship between nanostructure, free volume distributions, and optical properties, demonstrating the potential of these materials for advanced optoelectronic applications. The results of positron annihilation and Doppler broadening spectroscopes reveal crucial insights into the nanocomposites' porosity, free volume distribution, defect states, and their implications for optical applications. The AFM and UV-Vis results demonstrate that BETO nanoceramics enhance polyimide matrix's structural uniformity and optical properties, making them highly suitable for advanced optoelectronic applications. Barium Titanate free volume positron annihilation spectroscopy microstructural properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Polyimides (-CO-NR-CO-) are one of the most important engineering polymers widely used in advanced aerospace, electronics, and optical applications due to their excellent high-thermal stability dielectric and mechanical strength properties [ 1 – 2 ]. Polyimides like Kapton are typically synthesized from a reaction between aromatic anhydrides and aromatic diamines [ 3 ]. Ba₀.₉₅Eu₀.₀₅TiO₃ (BET), a doped BaTiO₃-based electroceramic, has a range of potential applications due to its enhanced structural, dielectric, and ferroelectric properties. The substitution of Eu³⁺ ions in the BaTiO₃ lattice introduces unique functional characteristics, making it suitable for advanced technologies such as multilayer ceramic capacitors (MLCCs) [ 4 ]. The XRD pattern indicates that BETO exhibits a perovskite-type structure, characteristic of BaTiO₃-based ceramics [ 5 ]. According to XRD analysis (Fig. 1 ), Ba²⁺ is bonded to twelve equivalent O²⁻ atoms to form BaO₁₂ cuboctahedra and faces eight equivalent TiO₆ octahedra. Incorporating functional nanoceramics, such as Ba₀.₉₅Eu₀.₀₅TiO₃, into polyimide matrices introduces additional functionalities, including tunable optical and dielectric properties [ 6 ]. Polyimide/Ba₀.₉₅Eu₀.₀₅TiO₃ (Polyimide /BETO) nanocomposites are known for their unique luminescent properties due to the presence of Eu 3 ⁺ ions, which exhibit strong photoluminescence in the visible range. Understanding the microstructural properties of these nanocomposites is crucial to optimizing their performance. The microstructural characteristics of these nanocomposites, including porosity, free volume distribution, and defect density, play a crucial role in determining their overall performance. Positron annihilation lifetime spectroscopy (PALS) [ 7 ] and variable energy positron beam (VEPB) [ 8 ] are powerful techniques commonly used in the study of free volume properties in materials, particularly polymers, nanomaterials, and porous structures. Positron annihilation, particularly in its fast and slow modes, is a powerful technique for probing these microstructural features. While the fast mode (PAL-Spectroscopy) provides information about bulk properties, the slow mode (VEPB techniques) enables depth-resolved analysis of surface and interfacial regions [ 9 ]. These parameters are directly correlated with the material's mechanical, electrical, and optical properties. The PAL-system measures positrons' lifetime before annihilating with electrons in material. The lifetime is sensitive to the size and distribution of free volumes, such as voids or pores, within the material. Specifically, in free volumes, positrons can form positronium (a bound state of a positron and an electron), which has a characteristic lifetime influenced by the size of the voids [ 10 , 11 ]. VEPB is a surface-sensitive extension of positron annihilation techniques that allows depth profiling of free volumes. This study investigates the microstructural and optical properties of polyimide-based nanocomposites filled with BETO nanoceramics at varying weight fractions (0%, 1%, 3%, 6%, and 9%). Using PALS and VEPB methods, we provide a comprehensive view of free volume properties across different scales and depths in Polyimide -BETO nanocomposites. 2. Materials and Methods 2.1. Materials The polyimide was used as the matrix material due to its exceptional thermal and mechanical properties. BETO nanoceramics were synthesized via sol-gel method, ensuring high purity and uniform particle size distribution. The BETO nanoparticles were incorporated into the polyimide matrix at concentrations of 1, 3, 6, and 9 wt%. 2.2. Nanocomposite Preparation Polymer-based solution : Polyimides are high-performance polymers with superior heat and chemical resistance, mainly used in advanced industries like aerospace and electronics. Using formic acid as a common solvent, we prepared the solution of the polyimides. We prepared a polymer-based solution by adding the polyimide (type: Nylon-6; amount: 8 wt% of the solution) into formic acid at 40 o C and under continuous stirring. Nanomaterial synthesis Ba 0.95 Eu 0.05 TiO 3 nanopowders were synthesized via the gel-combustion method. For this aim, first, barium acetate (Ba(CH 3 COO) 2 ·2H 2 O) dissolved in distilled water under constant stirring. To prepare Ti + 4 , we dissolved titanium isopropoxide Ti[OCH(CH 3 ) 2 ] 4 in a mixture of nitric, citric acid, and hydrogen peroxide. Separately, the solutions of europium nitrate (Eu(NO 3 ) 2 ) (0.05 wt%) were prepared using distilled water. The barium, titanium, and europium solutions were added to the aqueous solution of citric acid under continuous stirring at 55 o C. The pH of the sol (final solution) was maintained at 4.5 by adding ammonium. The sol was heated at 80°C to evaporate all the water, forming a homogeneous gel. Gel combustion was initiated by adding a small amount of nitric acid and removing residual water and moisture, forming a xerogel. The resulting white and black powders were then calcined at 800°C for 2 hours to promote the crystallization of BETO [ 12 ]. A detailed flow diagram of the nanopowders processing method used in this study is presented in Fig. 2 . Mixing Polyimide and Nanomaterial To ensure uniform dispersion of the nanoparticles, the BETO nanopowders dispersed in a small amount of the formic acid using ultrasound. Then, the dispersed nanopowders were added to the polyimide solution while stirring continuously. The nanocomposite films were prepared using a spin coater by depositing 0.5 mL of the mixture onto the center of the substrate. The final films were then cut into appropriate sizes and characterized for uniformity and particle dispersion using atomic force microscopy (AFM). 2.3. Optical Characterization The optical properties of the Polyimide/BETO nanocomposites were studied using UV-Vis spectroscopy to examine absorption behavior and photoluminescence (PL) measurements. The absorption, changes in the optical band gap, and emission spectra were analyzed to study the influence of BETO nanoceramics content on the optical behavior of the polyimide matrix. 2.4. Morphological Analysis AFM is an essential tool for the characterization of Polyimide/Ba 0.95 Eu 0.05 TiO₃ nanocomposites due to its capability to provide high-resolution surface morphology and roughness analysis. Surface morphology of Polyimide/BETO nanocomposites studied using AFM. Figure 4 shows the AFM images of the samples. As observed in Fig. 4 , the dispersion of BET nanoparticles identifies a little agglomeration at higher concentrations. 2.5. Positron Annihilation Lifetime Spectroscopy (PALS) Figure 5 illustrates the schematic of the PALS measurements conducted using a conventional setup. Fast positron annihilation was used to analyze the bulk free volume and defect density, while a variable-energy positron beam was employed for depth profiling of near-surface regions. The results were analyzed using PALSfit software [ 13 ] to determine positron lifetimes (τ) and intensities (I), indicative of free volume sizes and defect concentrations. 2.6. VEPB Characterization The variable energy positron beam (VEPB) characterization was performed to obtain depth information on the nanocomposites' microstructural properties. Different depths within the PI/BET were probed by varying the implantation energy of the positrons, ranging from the near-surface region to the bulk material. This method provides a detailed profile of free volume and defect density as a function of depth [ 14 ]. The results were analyzed to study the influence of BETO nanoceramic distribution and interfacial effects on the microstructure. This approach was particularly useful for identifying processing-induced defects and surface variations, offering insights beyond conventional bulk. 3. Results and Discussion 3.1. Morphological Observations AFM analyses confirmed uniform dispersion of BETO nanoparticles at lower concentrations (3 wt% and 6 wt%), while higher concentrations (9 wt%) exhibited slight agglomeration. These observations correlated well with the PALS data, which showed a higher defect density at 9 wt% BETO content. The interfacial regions between BETO nanoparticles and the polyimide matrix appeared to dominate the microstructural changes, as evidenced by enhanced free volume near the interfaces. 3.2. Optical Properties The gradual increase in the band gap from polyimide to Polyimide/BET-9wt% indicates that adding Ba 0.95 Eu 0.05 TiO₃/nanoparticles to the polyimide matrix systematically modifies the electronic structure of the nanocomposite. The observed trend suggests that the incorporation of BETO introduces new interactions between the polymer matrix and the filler, potentially reducing electronic states' density or altering the composite's charge carrier dynamics. The increasing band gap with BETO content implies improved nanocomposite insulating or dielectric properties; it makes the material suitable for applications in electronic packaging, high-performance capacitors, or insulating layers where a higher band gap is desirable [ 15 ]. While the band gap of Polyimide/BETO-9 wt% is significantly higher than that of pure Polyimide, it does not reach the level of pristine BETO. This suggests that the polyimide matrix still strongly influences the composite's overall electronic properties. 3.3. Microstructural Analysis The lifetime of o-Ps (τ 3 ) can be utilized to measure the size of the free volume, calculated using the Tao–Eldrup model [ 17 ]. In this model, the positronium quasi-atom (Ps) is assumed to reside within an unbounded spherical potential well with a radius of R. From the overlap integration of the positronium wave-function with the surrounding spherical electron layer of thickness ΔR, defined as ΔR = R 0 − R, the following relation is obtained: $$\:{{\tau\:}}_{3}=\frac{1}{2}{\left(1-\frac{\text{R}}{\text{R}+\varDelta\:\text{R}}+\frac{1}{2{\pi\:}}\text{sin}\frac{2{\pi\:}\text{R}}{\text{R}+\varDelta\:\text{R}}\right)}^{-1}$$ 1 Here, ΔR is an empirical parameter with a value of 0.165 nm. Using Eq. ( 1 ), the radius of the spherical free volume (R) can be calculated. Subsequently, the average free volume (ν f ) can be determined using the formula, \(\:{}_{\text{f}}\:=\:\frac{4{\text{R}}^{3}}{3}\) [ 18 ]. Additionally, the free volume fraction (F ν ), which has a linear relationship with the intensity (I 3 ) and the free volume, is expressed as [ 19 ]: $$\:{\text{F}}_{{\upsilon\:}}=\text{C}{.\text{I}}_{3}.{\text{V}}_{\text{p}\text{o}\text{r}\text{e}}\left({{\tau\:}}_{3}\right)$$ 2 Where C is a calibration constant, and V pore (τ 3 ) is the free volume associated with τ 3 , expressed in cubic angstroms (ų). The calculated values of R and F ν are presented in Table 1 . The results indicate that the free volume size, represented by τ 3 , increases linearly with the increasing BET content. However, adding BETO to the polyimide matrix does not result in a proportional increase in the free volume fraction, suggesting a non-linear relationship between BETO content and free volume enhancement. These findings provide insights into the role of BETO in modifying the free volume characteristics of Polyimide/BETO nanocomposites, with implications for their physical and mechanical properties. As shown in Table 1 , increasing the BETO concentration decreased the free volume fraction, indicating lower porosity (higher density) and a more tightly packed molecular structure in the Polyimide/BET composite. Table 1 Lifetime component (τ 3 ) and intensity (I 3 ) as a function of BETO content. Polyimide/BETO-x (wt%) τ 1 (ns) I 1 (%) τ 2 (ns) I 2 (%) τ 3 (ns) I 3 (%) R (nm) F V (%) x = 0.0 0.222 19.80 0.402 46.12 4.537 34.08 0.450 3.81 x = 1.0 0.229 20.83 0.413 44.85 4.439 34.32 0.445 3.69 x = 3.0 0.239 22.56 0.424 42.66 4.215 34.78 0.433 3.40 x = 6.0 0.251 24.62 0.431 40.27 4.187 35.11 0.432 3.37 x = 9.0 0.269 28.37 0.458 36.78 4.062 34.85 0.425 3.22 The combined optical and positron annihilation analyses revealed a clear relationship between microstructural modifications and optical properties. Specifically, incorporating BETO nanoceramics into the polyimide matrix enhances both the free volume characteristics and optical performance. The findings indicate that BETO nanoceramics increase the free volume density and reduce the optical band gap of the polyimide matrix. Among the tested compositions, the 6 wt% BETO nanocomposite demonstrated the optimal balance between structural uniformity and optical improvement, achieving a free volume of 3.37% and a band gap of 3.162 eV. This makes it highly suitable for ultraviolet (UV) applications, such as UV detectors, sterilization devices, and high-power optoelectronic components [ 20 ]. 4. Conclusion This study highlights the potential of Ba₀.₉₅Eu₀.₀₅TiO₃ nanoceramics as functional fillers for polyimide-based nanocomposites. This study provides a comprehensive analysis of polyimide-based nanocomposites incorporating BETO nanoceramics. The results of UV-Vis analysis show that the incorporation of BETO into polyimide gradually increases the material's band gap. This improvement in band gap highlights the potential of Polyimide/BETO nanocomposites for applications requiring high dielectric and insulating properties. Using advanced positron annihilation techniques, including PALS and VEPB analysis, we demonstrated the critical role of free volume and defect states in determining the materials' optical properties. The findings highlight the potential of these nanocomposites for optoelectronic applications, with the 6 wt% BETO formation showing the best performance. Declarations Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding Declaration: The authors declare that this research received no external funding. Author Contribution Mahdi Ghasemifard conceived of the presented idea, developed the theory and performed the computations, verified the analytical methods and encouraged Ugur Yahsi to supervise the findings of this work. Cumali Tav carried out the positron beam experiment. Misagh Ghamari carried out the Doppler broadening experiment and wrote the manuscript with support from Mahdi Ghasemifard. All authors discussed the results and contributed to the final manuscript. References J. Lin, J. Su, M. Weng, W. Xu, J. Huang, T. Fan, Y. Liu, Y. Min, 2023. Applications of flexible polyimide: Barrier material, sensor material, and functional material. Soft Sci., 3 (1), pp.N-A. V.G. Parale, T. Kim, H. Choi, V.D. Phadtare, R.P. Dhavale, K. Kanamori, H.H. Park, 2024. Mechanically strengthened aerogels through multiscale, multicompositional, and multidimensional approaches: A Review. Advanced Materials, 36(18), p.2307772 S.Y. Yang (ed.), Advanced polyimide materials: Synthesis, characterization, and applications (Elsevier, 2018) M. Ghasemifard, Investigating of the energy band of core electrons to identify the defects of BaTiO3 nanoelectroceramic doped with different concentrations of Nb element. Iran. J. Crystallogr. Mineralogy. 31 (4), 777–784 (2023) H.P. Beek, F. Müller, R. Haberkorn, D. Wilhelm, Synthesis of perovskite type compounds via different routes and their X-ray characterization. Nanostruct. Mater. 6 (5–8), 659–662 (1995) M. Ghasemifard, Investigating of the energy band of core electrons to identify the defects of BaTiO3 nanoelectroceramic doped with different concentrations of Nb element. Iran. J. Crystallogr. Mineralogy. 31 (4), 777–784 (2023) K.S. Liao, H. Chen, S. Awad, J.P. Yuan, W.S. Hung, K.R. Lee, J.Y. Lai, C.C. Hu, Y.C. Jean, Determination of free-volume properties in polymers without orthopositronium components in positron annihilation lifetime spectroscopy. Macromolecules. 44 (17), 6818–6826 (2011) S. McGuire, D.J. Keeble, R.E. Mason, P.G. Coleman, Y. Koutsonas, T.J. Jackson, 2006. low energy positron beam analysis of vacancy defects in laser ablated SrTiO 3 thin films on SrTiO 3 . J. Appl. Phys., 100 (4) L. Mathes, M. Suhr, V.V. Burwitz, D.R. Russell, S. Vohburger, C. Hugenschmidt, Surface and near-surface positron annihilation spectroscopy at very low positron energy. J. Instrum. 19 (11), P11026 (2024) Y. Yampolskii, V. Shantarovich, Positron annihilation lifetime spectroscopy and other methods for free volume evaluation in polymers (Materials science of membranes for gas and vapor separation, 2006), pp. 191–210 C. Li, B. Zhao, B. Zhou, N. Qi, Z. Chen, W. Zhou, Effects of electrical conductivity on the formation and annihilation of positronium in porous materials. Phys. Chem. Chem. Phys. 19 (11), 7659–7667 (2017) M. Ghasemifard, M. Ghamari, Chemical characterization of perovskite BaTiO 3 doped with different concentrations of Europium via coincidence doppler broadening spectroscopy. J. Electroceram. 52 (4), 297–302 (2024) J.V. Olsen, P. Kirkegaard, N.J. Pedersen, M. Eldrup, PALSfit: A new program for the evaluation of positron lifetime spectra. Phys. Status Solidi C 4 (10), 4004–4006 (2007) D.J. Keeble, DUNDEE, UNIV (UNITED KINGDOM), 2002. Defect Characterization of Pyroelectric Materials S. Chowdhury, E. Gurpinar, B. Ozpineci, Capacitor technologies: Characterization, selection, and packaging for next-generation power electronics applications. IEEE Trans. Transp. Electrification. 8 (2), 2710–2720 (2022) R. Hu, Y. Chen, C. Zhang, S. Jiang, H. Hou, G. Duan, 2024. Porous monoliths from polyimide: Synthesis, modifications and applications. Prog. Mater. Sci., p.101284 K. Wada, T. Hyodo, 2013, June. A simple shape-free model for pore-size estimation with positron annihilation lifetime spectroscopy. In Journal of Physics: Conference Series (Vol. 443, No. 1, p. 012003). IOP Publishing L. Wang, J. Sun, W. Yang, R. Tian, Analytic Equation of State and Thermodynamic Properties, for α-, β-, and γ-Si₃N₄ Based on Analytic Mean Field Approach. Acta Phys. Pol., A 114 (4), 807–818 (2008) O.M. Blaes, 2004. Course 3: Physics fundamentals of luminous accretion disks around black holes. Accretion discs, jets and high energy phenomena in astrophysics: Les Houches Session LXXVIII, 29 July-23 August, 2002 (137–185). Berlin, Heidelberg: Springer Berlin Heidelberg T. Bhattarai, A. Ebong, M.Y.A. Raja, 2024, May. A Review of Light-Emitting Diodes and Ultraviolet Light-Emitting Diodes and Their Applications. In Photonics . 11, 6, 491). MDPI Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6859860","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":477095905,"identity":"c3d4bbfa-2be2-4e59-86fa-90d0055120da","order_by":0,"name":"Mahdi Ghasemifard","email":"data:image/png;base64,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","orcid":"","institution":"Esfarayen University of Technology","correspondingAuthor":true,"prefix":"","firstName":"Mahdi","middleName":"","lastName":"Ghasemifard","suffix":""},{"id":477095906,"identity":"5505a785-4944-455b-aefa-fd27b4931ea2","order_by":1,"name":"Misagh Ghamari","email":"","orcid":"","institution":"Esfarayen University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Misagh","middleName":"","lastName":"Ghamari","suffix":""},{"id":477095907,"identity":"dafef87e-79dc-45fa-ab5e-9901db184f6f","order_by":2,"name":"Cumali Tav","email":"","orcid":"","institution":"Marmara University","correspondingAuthor":false,"prefix":"","firstName":"Cumali","middleName":"","lastName":"Tav","suffix":""},{"id":477095908,"identity":"5ff55e9d-fa39-4bd8-8384-fc55c6b53eca","order_by":3,"name":"Ugur Yahsi","email":"","orcid":"","institution":"Marmara University","correspondingAuthor":false,"prefix":"","firstName":"Ugur","middleName":"","lastName":"Yahsi","suffix":""}],"badges":[],"createdAt":"2025-06-10 06:53:25","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6859860/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6859860/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":85559937,"identity":"755c549d-6779-48c9-a2a1-cf507423d21e","added_by":"auto","created_at":"2025-06-27 12:25:38","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1542622,"visible":true,"origin":"","legend":"\u003cp\u003eBa₀.₉₅Eu₀.₀₅TiO₃ nanopowders characterization: (a) XRD, (b) a typical unit cell of a perovskite structure, (c) TEM and (d) Uv-Vis.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6859860/v1/9e272ccc5a7324cfc0fb019f.png"},{"id":85559964,"identity":"2a1d3df5-8dfc-4b6e-a7ca-3cccbcac1475","added_by":"auto","created_at":"2025-06-27 12:25:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":3531301,"visible":true,"origin":"","legend":"\u003cp\u003eFlow diagram for BETO nanopowders and Polyimide /BETOnanocomposites preparation procedure.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6859860/v1/d2bcb65a3322e8115b1e7633.png"},{"id":85559968,"identity":"8bd11a86-85a8-4f08-bdd7-91d074240bad","added_by":"auto","created_at":"2025-06-27 12:25:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":881084,"visible":true,"origin":"","legend":"\u003cp\u003eUV-Vis spectra of Polyimide /BETO nanocomposites. The inset is the dependence of the absorption coefficients (αhν)\u003csup\u003e2\u003c/sup\u003e on the photon energy, the band gap values for different samples of polyimide and its nanocomposites with BETO.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6859860/v1/a451729b4b66fde51f53b1f3.png"},{"id":85559950,"identity":"25602703-688f-44f7-bf5c-6b16eb1d5154","added_by":"auto","created_at":"2025-06-27 12:25:38","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2896606,"visible":true,"origin":"","legend":"\u003cp\u003eSurface roughness and three-dimensional topographic images of the composite's surface, revealing the distribution of BETOnanoparticles within the polyimide matrix. (a) 0.0 wt%, (b) 1.0 wt%, (c) 3.0 wt%, (d) 6.0 wt%, and (e) 9.0 wt%.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6859860/v1/9e954d7f766d00b072d25136.png"},{"id":85559947,"identity":"bc403ad2-cd62-4187-8e99-3d6516e91958","added_by":"auto","created_at":"2025-06-27 12:25:38","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1373716,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Experimental of an electronic circuit of PALS, (b) PALSfit program results for Polyimide/BETO-0.6 wt%, and (c) total PALS spectra for all samples.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6859860/v1/da1d1128528d512a5a1ac7d6.png"},{"id":85559966,"identity":"387fb01c-7263-4982-b1c9-263b17a55fd9","added_by":"auto","created_at":"2025-06-27 12:25:38","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1370077,"visible":true,"origin":"","legend":"\u003cp\u003e(a) VEPB spectra analyzed by SP software. (b) Longitudinal axis zooms in, (c) W parameter vs. S parameter (with increase BETO content, S parameter reduces and W parameter increases), and (d) P parameter vs. positron energy (or mean depth) data for Polyimide/BETO nanocomposites.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-6859860/v1/1866497838bb1545e063a80a.png"},{"id":87581702,"identity":"da1bed97-5c8f-4695-8099-d980d4e9d03b","added_by":"auto","created_at":"2025-07-25 13:02:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":11395365,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6859860/v1/6ab7d83a-6535-49ac-ac55-e2f99248d7cb.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Microstructural analysis of polyimide-based nanocomposite with BaTiO 3 :Eu nanoceramics using high and low positron annihilation techniques","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePolyimides (-CO-NR-CO-) are one of the most important engineering polymers widely used in advanced aerospace, electronics, and optical applications due to their excellent high-thermal stability dielectric and mechanical strength properties [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Polyimides like Kapton are typically synthesized from a reaction between aromatic anhydrides and aromatic diamines [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Ba₀.₉₅Eu₀.₀₅TiO₃ (BET), a doped BaTiO₃-based electroceramic, has a range of potential applications due to its enhanced structural, dielectric, and ferroelectric properties. The substitution of Eu\u0026sup3;⁺ ions in the BaTiO₃ lattice introduces unique functional characteristics, making it suitable for advanced technologies such as multilayer ceramic capacitors (MLCCs) [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The XRD pattern indicates that BETO exhibits a perovskite-type structure, characteristic of BaTiO₃-based ceramics [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. According to XRD analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), Ba\u0026sup2;⁺ is bonded to twelve equivalent O\u0026sup2;⁻ atoms to form BaO₁₂ cuboctahedra and faces eight equivalent TiO₆ octahedra. Incorporating functional nanoceramics, such as Ba₀.₉₅Eu₀.₀₅TiO₃, into polyimide matrices introduces additional functionalities, including tunable optical and dielectric properties [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Polyimide/Ba₀.₉₅Eu₀.₀₅TiO₃ (Polyimide /BETO) nanocomposites are known for their unique luminescent properties due to the presence of Eu\u003csup\u003e3\u003c/sup\u003e⁺ ions, which exhibit strong photoluminescence in the visible range. Understanding the microstructural properties of these nanocomposites is crucial to optimizing their performance. The microstructural characteristics of these nanocomposites, including porosity, free volume distribution, and defect density, play a crucial role in determining their overall performance. Positron annihilation lifetime spectroscopy (PALS) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and variable energy positron beam (VEPB) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] are powerful techniques commonly used in the study of free volume properties in materials, particularly polymers, nanomaterials, and porous structures. Positron annihilation, particularly in its fast and slow modes, is a powerful technique for probing these microstructural features. While the fast mode (PAL-Spectroscopy) provides information about bulk properties, the slow mode (VEPB techniques) enables depth-resolved analysis of surface and interfacial regions [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. These parameters are directly correlated with the material's mechanical, electrical, and optical properties. The PAL-system measures positrons' lifetime before annihilating with electrons in material. The lifetime is sensitive to the size and distribution of free volumes, such as voids or pores, within the material. Specifically, in free volumes, positrons can form positronium (a bound state of a positron and an electron), which has a characteristic lifetime influenced by the size of the voids [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. VEPB is a surface-sensitive extension of positron annihilation techniques that allows depth profiling of free volumes.\u003c/p\u003e \u003cp\u003eThis study investigates the microstructural and optical properties of polyimide-based nanocomposites filled with BETO nanoceramics at varying weight fractions (0%, 1%, 3%, 6%, and 9%). Using PALS and VEPB methods, we provide a comprehensive view of free volume properties across different scales and depths in Polyimide -BETO nanocomposites.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Materials\u003c/h2\u003e \u003cp\u003eThe polyimide was used as the matrix material due to its exceptional thermal and mechanical properties. BETO nanoceramics were synthesized via sol-gel method, ensuring high purity and uniform particle size distribution. The BETO nanoparticles were incorporated into the polyimide matrix at concentrations of 1, 3, 6, and 9 wt%.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Nanocomposite Preparation\u003c/h2\u003e \u003cp\u003e \u003cb\u003ePolymer-based solution\u003c/b\u003e: Polyimides are high-performance polymers with superior heat and chemical resistance, mainly used in advanced industries like aerospace and electronics. Using formic acid as a common solvent, we prepared the solution of the polyimides. We prepared a polymer-based solution by adding the polyimide (type: Nylon-6; amount: 8 wt% of the solution) into formic acid at 40 \u003csup\u003eo\u003c/sup\u003eC and under continuous stirring.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eNanomaterial synthesis\u003c/strong\u003e \u003cp\u003eBa\u003csub\u003e0.95\u003c/sub\u003eEu\u003csub\u003e0.05\u003c/sub\u003eTiO\u003csub\u003e3\u003c/sub\u003e nanopowders were synthesized via the gel-combustion method. For this aim, first, barium acetate (Ba(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO) dissolved in distilled water under constant stirring. To prepare Ti\u003csup\u003e+\u0026thinsp;4\u003c/sup\u003e, we dissolved titanium isopropoxide Ti[OCH(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e4\u003c/sub\u003e in a mixture of nitric, citric acid, and hydrogen peroxide. Separately, the solutions of europium nitrate (Eu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e) (0.05 wt%) were prepared using distilled water. The barium, titanium, and europium solutions were added to the aqueous solution of citric acid under continuous stirring at 55 \u003csup\u003eo\u003c/sup\u003eC. The pH of the sol (final solution) was maintained at 4.5 by adding ammonium. The sol was heated at 80\u0026deg;C to evaporate all the water, forming a homogeneous gel. Gel combustion was initiated by adding a small amount of nitric acid and removing residual water and moisture, forming a xerogel. The resulting white and black powders were then calcined at 800\u0026deg;C for 2 hours to promote the crystallization of BETO [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. A detailed flow diagram of the nanopowders processing method used in this study is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eMixing Polyimide and Nanomaterial\u003c/strong\u003e \u003cp\u003eTo ensure uniform dispersion of the nanoparticles, the BETO nanopowders dispersed in a small amount of the formic acid using ultrasound. Then, the dispersed nanopowders were added to the polyimide solution while stirring continuously. The nanocomposite films were prepared using a spin coater by depositing 0.5 mL of the mixture onto the center of the substrate. The final films were then cut into appropriate sizes and characterized for uniformity and particle dispersion using atomic force microscopy (AFM).\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Optical Characterization\u003c/h2\u003e \u003cp\u003eThe optical properties of the Polyimide/BETO nanocomposites were studied using UV-Vis spectroscopy to examine absorption behavior and photoluminescence (PL) measurements. The absorption, changes in the optical band gap, and emission spectra were analyzed to study the influence of BETO nanoceramics content on the optical behavior of the polyimide matrix.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Morphological Analysis\u003c/h2\u003e \u003cp\u003eAFM is an essential tool for the characterization of Polyimide/Ba\u003csub\u003e0.95\u003c/sub\u003eEu\u003csub\u003e0.05\u003c/sub\u003eTiO₃ nanocomposites due to its capability to provide high-resolution surface morphology and roughness analysis. Surface morphology of Polyimide/BETO nanocomposites studied using AFM. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the AFM images of the samples. As observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the dispersion of BET nanoparticles identifies a little agglomeration at higher concentrations.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Positron Annihilation Lifetime Spectroscopy (PALS)\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e illustrates the schematic of the PALS measurements conducted using a conventional setup. Fast positron annihilation was used to analyze the bulk free volume and defect density, while a variable-energy positron beam was employed for depth profiling of near-surface regions. The results were analyzed using PALSfit software [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] to determine positron lifetimes (τ) and intensities (I), indicative of free volume sizes and defect concentrations.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6. VEPB Characterization\u003c/h2\u003e \u003cp\u003eThe variable energy positron beam (VEPB) characterization was performed to obtain depth information on the nanocomposites' microstructural properties. Different depths within the PI/BET were probed by varying the implantation energy of the positrons, ranging from the near-surface region to the bulk material. This method provides a detailed profile of free volume and defect density as a function of depth [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The results were analyzed to study the influence of BETO nanoceramic distribution and interfacial effects on the microstructure. This approach was particularly useful for identifying processing-induced defects and surface variations, offering insights beyond conventional bulk.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Morphological Observations\u003c/h2\u003e \u003cp\u003eAFM analyses confirmed uniform dispersion of BETO nanoparticles at lower concentrations (3 wt% and 6 wt%), while higher concentrations (9 wt%) exhibited slight agglomeration. These observations correlated well with the PALS data, which showed a higher defect density at 9 wt% BETO content. The interfacial regions between BETO nanoparticles and the polyimide matrix appeared to dominate the microstructural changes, as evidenced by enhanced free volume near the interfaces.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Optical Properties\u003c/h2\u003e \u003cp\u003eThe gradual increase in the band gap from polyimide to Polyimide/BET-9wt% indicates that adding Ba\u003csub\u003e0.95\u003c/sub\u003eEu\u003csub\u003e0.05\u003c/sub\u003eTiO₃/nanoparticles to the polyimide matrix systematically modifies the electronic structure of the nanocomposite. The observed trend suggests that the incorporation of BETO introduces new interactions between the polymer matrix and the filler, potentially reducing electronic states' density or altering the composite's charge carrier dynamics. The increasing band gap with BETO content implies improved nanocomposite insulating or dielectric properties; it makes the material suitable for applications in electronic packaging, high-performance capacitors, or insulating layers where a higher band gap is desirable [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. While the band gap of Polyimide/BETO-9 wt% is significantly higher than that of pure Polyimide, it does not reach the level of pristine BETO. This suggests that the polyimide matrix still strongly influences the composite's overall electronic properties.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Microstructural Analysis\u003c/h2\u003e \u003cp\u003eThe lifetime of o-Ps (τ\u003csub\u003e3\u003c/sub\u003e) can be utilized to measure the size of the free volume, calculated using the Tao\u0026ndash;Eldrup model [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. In this model, the positronium quasi-atom (Ps) is assumed to reside within an unbounded spherical potential well with a radius of R. From the overlap integration of the positronium wave-function with the surrounding spherical electron layer of thickness ΔR, defined as ΔR\u0026thinsp;=\u0026thinsp;R\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;\u0026minus;\u0026thinsp;R, the following relation is obtained:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{{\\tau\\:}}_{3}=\\frac{1}{2}{\\left(1-\\frac{\\text{R}}{\\text{R}+\\varDelta\\:\\text{R}}+\\frac{1}{2{\\pi\\:}}\\text{sin}\\frac{2{\\pi\\:}\\text{R}}{\\text{R}+\\varDelta\\:\\text{R}}\\right)}^{-1}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eHere, ΔR is an empirical parameter with a value of 0.165 nm. Using Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), the radius of the spherical free volume (R) can be calculated. Subsequently, the average free volume (ν\u003csub\u003ef\u003c/sub\u003e) can be determined using the formula, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{}_{\\text{f}}\\:=\\:\\frac{4{\\text{R}}^{3}}{3}\\)\u003c/span\u003e\u003c/span\u003e [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Additionally, the free volume fraction (F\u003csub\u003eν\u003c/sub\u003e), which has a linear relationship with the intensity (I\u003csub\u003e3\u003c/sub\u003e) and the free volume, is expressed as [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{\\text{F}}_{{\\upsilon\\:}}=\\text{C}{.\\text{I}}_{3}.{\\text{V}}_{\\text{p}\\text{o}\\text{r}\\text{e}}\\left({{\\tau\\:}}_{3}\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere C is a calibration constant, and V\u003csub\u003epore\u003c/sub\u003e(τ\u003csub\u003e3\u003c/sub\u003e) is the free volume associated with τ\u003csub\u003e3\u003c/sub\u003e, expressed in cubic angstroms (\u0026Aring;\u0026sup3;). The calculated values of R and F\u003csub\u003eν\u003c/sub\u003e are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The results indicate that the free volume size, represented by τ\u003csub\u003e3\u003c/sub\u003e, increases linearly with the increasing BET content. However, adding BETO to the polyimide matrix does not result in a proportional increase in the free volume fraction, suggesting a non-linear relationship between BETO content and free volume enhancement. These findings provide insights into the role of BETO in modifying the free volume characteristics of Polyimide/BETO nanocomposites, with implications for their physical and mechanical properties. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, increasing the BETO concentration decreased the free volume fraction, indicating lower porosity (higher density) and a more tightly packed molecular structure in the Polyimide/BET composite.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLifetime component (τ\u003csub\u003e3\u003c/sub\u003e) and intensity (I\u003csub\u003e3\u003c/sub\u003e) as a function of BETO content.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePolyimide/BETO-x (wt%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eτ\u003csub\u003e1\u003c/sub\u003e (ns)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI\u003csub\u003e1\u003c/sub\u003e (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eτ\u003csub\u003e2\u003c/sub\u003e (ns)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eI\u003csub\u003e2\u003c/sub\u003e (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eτ\u003csub\u003e3\u003c/sub\u003e (ns)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eI\u003csub\u003e3\u003c/sub\u003e (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eR (nm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eF\u003csub\u003eV\u003c/sub\u003e (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ex\u0026thinsp;=\u0026thinsp;0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.222\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e19.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.402\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e46.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4.537\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e34.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.450\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e3.81\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e 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\u003cp\u003ex\u0026thinsp;=\u0026thinsp;9.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.269\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.458\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e36.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4.062\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e34.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.425\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e3.22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe combined optical and positron annihilation analyses revealed a clear relationship between microstructural modifications and optical properties. Specifically, incorporating BETO nanoceramics into the polyimide matrix enhances both the free volume characteristics and optical performance. The findings indicate that BETO nanoceramics increase the free volume density and reduce the optical band gap of the polyimide matrix. Among the tested compositions, the 6 wt% BETO nanocomposite demonstrated the optimal balance between structural uniformity and optical improvement, achieving a free volume of 3.37% and a band gap of 3.162 eV. This makes it highly suitable for ultraviolet (UV) applications, such as UV detectors, sterilization devices, and high-power optoelectronic components [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThis study highlights the potential of Ba₀.₉₅Eu₀.₀₅TiO₃ nanoceramics as functional fillers for polyimide-based nanocomposites. This study provides a comprehensive analysis of polyimide-based nanocomposites incorporating BETO nanoceramics. The results of UV-Vis analysis show that the incorporation of BETO into polyimide gradually increases the material's band gap. This improvement in band gap highlights the potential of Polyimide/BETO nanocomposites for applications requiring high dielectric and insulating properties. Using advanced positron annihilation techniques, including PALS and VEPB analysis, we demonstrated the critical role of free volume and defect states in determining the materials' optical properties. The findings highlight the potential of these nanocomposites for optoelectronic applications, with the 6 wt% BETO formation showing the best performance.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eDeclaration of interests\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eDeclaration:\u003c/p\u003e \u003cp\u003eThe authors declare that this research received no external funding.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eMahdi Ghasemifard conceived of the presented idea, developed the theory and performed the computations, verified the analytical methods and encouraged Ugur Yahsi to supervise the findings of this work. Cumali Tav carried out the positron beam experiment. Misagh Ghamari carried out the Doppler broadening experiment and wrote the manuscript with support from Mahdi Ghasemifard. All authors discussed the results and contributed to the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eJ. Lin, J. Su, M. Weng, W. Xu, J. Huang, T. Fan, Y. Liu, Y. Min, 2023. Applications of flexible polyimide: Barrier material, sensor material, and functional material. Soft Sci., \u003cb\u003e3\u003c/b\u003e(1), pp.N-A.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eV.G. Parale, T. Kim, H. Choi, V.D. Phadtare, R.P. Dhavale, K. Kanamori, H.H. Park, 2024. Mechanically strengthened aerogels through multiscale, multicompositional, and multidimensional approaches: A Review. Advanced Materials, 36(18), p.2307772\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS.Y. Yang (ed.), \u003cem\u003eAdvanced polyimide materials: Synthesis, characterization, and applications\u003c/em\u003e (Elsevier, 2018)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. Ghasemifard, Investigating of the energy band of core electrons to identify the defects of BaTiO3 nanoelectroceramic doped with different concentrations of Nb element. Iran. J. Crystallogr. Mineralogy. \u003cb\u003e31\u003c/b\u003e(4), 777\u0026ndash;784 (2023)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eH.P. Beek, F. M\u0026uuml;ller, R. Haberkorn, D. Wilhelm, Synthesis of perovskite type compounds via different routes and their X-ray characterization. Nanostruct. Mater. \u003cb\u003e6\u003c/b\u003e(5\u0026ndash;8), 659\u0026ndash;662 (1995)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. Ghasemifard, Investigating of the energy band of core electrons to identify the defects of BaTiO3 nanoelectroceramic doped with different concentrations of Nb element. 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Course 3: Physics fundamentals of luminous accretion disks around black holes. \u003cem\u003eAccretion discs, jets and high energy phenomena in astrophysics: Les Houches Session LXXVIII, 29 July-23 August, 2002\u003c/em\u003e (137\u0026ndash;185). Berlin, Heidelberg: Springer Berlin Heidelberg\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eT. Bhattarai, A. Ebong, M.Y.A. Raja, 2024, May. A Review of Light-Emitting Diodes and Ultraviolet Light-Emitting Diodes and Their Applications. In \u003cem\u003ePhotonics\u003c/em\u003e. 11, 6, 491). MDPI\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Barium Titanate, free volume, positron annihilation spectroscopy, microstructural properties","lastPublishedDoi":"10.21203/rs.3.rs-6859860/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6859860/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates the microstructural properties of polyimide-based nanocomposites filled with Ba₀.₉₅Eu₀.₀₅TiO₃ (BETO) nanoceramics using advanced positron annihilation in fast and slow modes. The addition of BETO nanoceramics introduces unique free volume characteristics and defect states, which are critical to increasing the optical and structural performance of the nanocomposites. It explores the relationship between nanostructure, free volume distributions, and optical properties, demonstrating the potential of these materials for advanced optoelectronic applications. The results of positron annihilation and Doppler broadening spectroscopes reveal crucial insights into the nanocomposites' porosity, free volume distribution, defect states, and their implications for optical applications. The AFM and UV-Vis results demonstrate that BETO nanoceramics enhance polyimide matrix's structural uniformity and optical properties, making them highly suitable for advanced optoelectronic applications.\u003c/p\u003e","manuscriptTitle":"Microstructural analysis of polyimide-based nanocomposite with BaTiO 3 :Eu nanoceramics using high and low positron annihilation techniques","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-27 12:25:33","doi":"10.21203/rs.3.rs-6859860/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"de0a0464-cd87-47ad-a83b-07ac466a9f7f","owner":[],"postedDate":"June 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-25T12:54:02+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-27 12:25:33","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6859860","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6859860","identity":"rs-6859860","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}