Comparative investigations on dielectric, piezoelectric properties and humidity resistance of PZT–SKN and PZT–SNN ceramics

Sodium was used to substituted for potassium in Pb(Zr_0.53,Ti_0.47)O₃–Sr(K_0.25,Nb_0.75)O₃ (PZT–SKN) based on the lead-free (Na_0.5K_0.5)NbO₃ (KNN) piezoelectric ceramic and a new ceramic material Pb(Zr_0.53,Ti_0.47)O₃–Sr(Na_0.25,Nb_0.75)O₃ (PZT–SNN) was developed in order to improve the humidity resistance. PZT–SKN and PZT–SNN ceramics have been fabricated by the conventional solid-state reaction method at the sintering temperature of 1,150–1,225 °C for 2 h. The effects of SKN and SNN on the microstructure, piezoelectric properties and humidity resistance of the prepared ceramics have been systematically investigated and compared. The phase structures of the two ceramics are both tetragonal. With increasing of SKN/SNN, both the grain size and Curie temperature decrease. Among all compositions studied, the 0.99PZT–0.01SKN and 0.98PZT–0.02SNN sintered at 1,175 °C exhibited optimal comprehensive properties. Especially, the PZT–SNN has a higher humidity resistance than PZT–SKN. The optimal values of d ₃₃, kp, ε _r and Tc for 0.98PZT–0.02SNN is 448pC/N, 0.63, 2,126.32 and 354 °C, respectively.