Piezoelectric Thermal Stability of (KxNa1-x)NbO3 Based Ceramics

Lead-free piezoelectric ceramics (KxNa1-x)1-yLiyNb0.80Ta0.20O3 (x=0.40∼0.60; y=0.03, 0.035, 0.04) were prepared by a conventional solid-state reaction method, and the thermal stability of piezoelectric properties was investigated. Results show that samples in the researched compositional range have high piezoelectric constant of d33=250 pC/N and kp=50%. In the thermal aging test up to the Curie temperature of approximately 325 oC, d33 and kp of the ceramics remain almost unchanged although there is polymorphic phase transition (PPT) near room temperature. Moreover, the ceramics present the very good piezoelectric temperature stability and kp shows a weak temperature dependence over a wide measured temperature range from −50 °C to 120 °C. The excellent thermal stability was discussed from the aspect of temperature range of phase coexistence