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 Li_0.06(Na_0.535K_0.48)_0.94NbO₃+0.7mol% ZnO (LNKN-Z₇) was synthesized normally at 930-1000℃. 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℃. Because of such transitional behavior and fine microstructure, the optimized values of piezoelectric coefficient, planar electromechanical coupling coefficient, and relative dielectric constant were obtained.