Effect of CuO on the sintering temperature and piezoelectric properties of lead-free 0.95(Na0.5K0.5)NbO3–0.05CaTiO3 ceramics

The addition of a small amount of CuO to the 0.95(Na0.5K0.5)NbO3–0.05CaTiO3 (0.95NKN–0.05CT) ceramics sintered at 960 °C for 10 h produced a dense microstructure with large grains due to the liquid phase sintering. Due to the negligible Na2O evaporation, poling was easy for all specimens sintered at 960 °C. The piezoelectric properties of the specimens were considerably influenced by the relative density, grain size and liquid phase amount. The high piezoelectric properties of d33 = 200 pC/N, kp = 0.37, ε3T/ε0=1173 and Qm = 350 were obtained for the 0.95NKN–0.05CT ceramics containing 2.0 mol% CuO sintered at 960 °C for 10 h. Therefore, the 0.95NKN–0.05CT ceramics containing a small amount of CuO are a good candidate material for lead-free piezoelectric ceramics.