Effects of Li2CO3 and Bi2O3 additives on sintering temperature and piezoelectric properties of PNIN-PCW-PZT ceramics for multilayer piezoelectric transformer

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, PCW-PMN-PZT ceramics doped with Li₂CO₃, Bi₂O₃ and CuO as sintering aids were manufactured, and their microstructural, dielectric and piezoelectric properties were investigated. When the only CuO was added, specimens could not be sintered below 980°C. However, when Li₂CO₃ and Bi₂O₃ were added, specimens could be sintered below 980°C. Li₂CO₃ and Bi₂O₃ addition were proved to lower sintering temperature of piezoelectric ceramics due to the effect of Li₂O-Bi₂O₃ liquid phase. Li₂CO₃ and Bi₂O₃ added specimens showed higher piezoelectric properties than those of the only CuO added specimens. At 0.2wt% Li₂CO₃ and 0.3wt% Bi₂O₃ added specimen sintered at 920°C, the dielectric constant (ε_r) of 1457, electromechanical coupling factor (k_p) of 0.56 and mechanical quality factor (Q_m) of 1000 were shown, respectively. These values are suitable for multilayer piezoelectric transformer application.