Effects of ZnO/Li2O codoping on microstructure and piezoelectric properties of low-temperature sintered PMN–PNN–PZT ceramics

Pb(Mg1/3Nb2/3)O3–Pb(Ni1/3Nb2/3)O3–Pb(Zr1/2Ti1/2)O3 (designated as PMNT) piezoelectric ceramics codoping with Zn2+/Li+ were prepared and the effects of ZnO/Li2O (Z/L) additive on microstructure, piezoelectric and dielectric properties were investigated. The results show that the pure perovskite phase is formed and the phase structure changes from tetragonal to rhombohedral with different Z/L weight ratios. The Curie temperature Tc, dielectric constant ɛ, electromechanical coupling factor kp and piezoelectric constant d33 decrease, whereas mechanical quality factor Qm increases with Z/L weight ratio changing from 1:1 to 1:8. The optimized Z/L weight ratio is 1:1. It is revealed that kp and d33 first increase then decrease, whereas Qm changes opposite with increasing content of Z/L additive. The PMNT ceramic with Z/L ratio 1:1 and the amount of 1 wt% has excellent piezoelectric properties: kp = 0.60, d33 = 397 pC/N, Tc = 251 °C, Qm = 150, ɛ = 2628 and tan δ = 0.0296, when sintered at 960 °C. Finally, multilayer piezoelectric actuator is prepared using optimal composition by tape casting. The actuator shows the displacement characteristics of 3.3 μm under electric field 100 V/mm.