Effect of CuO on the Sintering and Piezoelectric Properties of 0.95(Na0.5K0.5)NbO3-0.05SrTiO(3) Lead-Free Piezoelectric Ceramics

Abstract

CuO was used to enhance the sinterability of 0.95(Na0.5K0.5)NbO3-0.05SrTiO(3) (0.95NKN-0.05ST) ceramics. The poor sinterability of 0.95NKN-0.05ST ceramics was improved by the addition of 1.5 mol% CuO, so that they were well sintered even at 960 degrees C with grain growth. The densification and grain growth were attributed to liquid-phase sintering, probably due to the presence of a liquid phase containing SrO and CuO. The grain size decreased when the sintering temperature exceeded 960 degrees C, due to the presence of a large amount of liquid phase. The microstructure of the 0.95NKN-0.05ST ceramics was considerably affected by even small variations of sintering temperature. The d(33), k(p), and Q(m) values increased with CuO addition due to the increased density and grain size. The high piezoelectric properties of k(p)=0.35, d(33)=200, and epsilon(T)(33)/epsilon(o)=1235 were obtained from the 0.95NKN-0.05ST ceramics containing 1.5 mol% CuO sintered at 960 degrees C for 10 h.