Influence of sintering temperature on the structure and piezoelectric properties of ZnO-modified (Li, Na, K)NbO3 lead-free ceramics

ZnO-modified (Li, Na, K)NbO3 lead-free ceramics with a nominal composition of Li0.06(Na0.535K0.48)0.94NbO3+0.7mol% ZnO (LNKN-Z7) was synthesized normally at 930–1000°C. The Zn ions incorporated into the A-site at a higher sintering temperature, which changed LNKN-Z7 to soft piezoelectric ceramics with the mechanical quality factor decreasing from 228 to 192. A phase transition from tetragonal to orthorhombic symmetry was identified by XRD analysis, and the corresponding calculation of lattice parameters was conducted at 970–980°C. Because of such transitional behavior and fine microstructure, the optimized values of piezoelectric coefficient, planar electromechanical coupling coefficient, and relative dielectric constant were obtained.