Microstructure, temperature stability and electrical properties of ZnO-modified Pb(Ni1/3Nb2/3)O3–Pb(Fe1/2Nb1/2)O3–Pb(Zr0.3Ti0.7)O3 piezoelectric ceramics

Quaternary piezoelectric ceramics Pb(Ni1/3Nb2/3)O3–Pb(Fe1/2Nb1/2)O3–Pb(Zr0.3Ti0.7)O3–xZnO (PNN–PFN–PZT–xZ, x=0.0–0.08 in molar ratio) were prepared by the conventional mixed-oxide method. The effects of ZnO content on the microstructure and piezoelectric properties were systematically investigated. Increasing ZnO additive promotes the phase structure transformation from rhombohedral to tetragonal, indicating the presence of the morphotropic phase boundary in the ZnO-modified PNN–PFN–PZT system. The results show that ZnO doping significantly improves the coercive field (Ec), Curie temperature (Tc), and temperature stability (Δfr/fr 30 °C, Δd31/d31 30 °C) of the PNN–PFN–PZT–xZ ceramics, although the piezoelectric constant (d33, d31) decreases slightly with increasing ZnO content. Taking into consideration the piezoelectric property and temperature stability, the obtained ceramic sample with x=0.04 exhibited favorable properties, which are listed as follows: d33=810 pC/N, kp=0.647, εr=6243, tan δ=2.74%, Ec=4.7 kV/cm, and Tc=136 °C.