Precipitation Hardening of La Doped BaTiO₃ Piezoelectric Ceramics based on Redox Reaction

In resonant applications, mechanical loss is one of the key factors affecting the performance of devices. Excessive mechanical loss can significantly degrade the piezoelectric effect. Therefore, piezoelectric hardening is commonly employed to reduce mechanical loss, ensuring stable operation of the devices under high-frequency resonant conditions. In this paper, we prepared (Ba_0.96 La_0.04)0.96 TiO₃ ceramics. Due to the high solubility of La in reducing conditions and low solubility in oxidizing conditions, the samples can be sintered in reducing conditions to make La dissolve in the matrix phase firstly. Then, these samples were heat-treated in air, causing a portion of the La compounds to precipitate. X-ray diffraction analysis revealed alterations in the crystal structure and the emergence of characteristic peaks corresponding to the second phase in the reoxidized samples. The piezoelectric ceramics containing the precipitated phase exhibited a significant improvement in the mechanical quality factor (Q_m), and a reduction in both the saturation polarization (P_s) and remnant polarization (Pr) in the polarization-electric field (P-E) hysteresis loops. The precipitation hardening piezoelectric ceramics prepared by this method effectively suppress the domain wall motion and provide a new method for the preparation of high-performance piezoelectric ceramics for high power applications.