Composite Hardening Effect in KNN Piezoelectric Ceramics

This study investigates the preparation of KNN-ZnO composites through optimized sintering conditions under both inert and oxygen atmospheres. Initial experiments employing inert hot pressing were hindered by the necessity for annealing, which resulted in cracks due to the differing thermal expansion coefficients of KNN and ZnO, rendering this method unsuitable for composite fabrication. Consequently, sintering under an oxygen atmosphere was adopted, yielding a uniform distribution of ZnO particles within the KNN matrix. The resultant microstructure demonstrated significant densification, enhanced homogeneity, and minimal porosity. Electrical performance evaluations revealed that while the incorporation of ZnO led to a slight reduction in the ferroelectric properties (d33 and polarization) of the KNN matrix, it concurrently improved the electromechanical quality factor (Qm) by 40%. However, the overall enhancements were less pronounced when compared to analogous BNT-BT systems, underscoring the necessity for further optimization of processing conditions to boost electromechanical efficiency and piezoelectric response in KNN-based ceramics.