Brief Review of Lead-Free Piezoelectric Ceramics for High-Power Applications

Lead-free piezoelectric ceramics have gained significant attention as environmentally friendly alternatives to lead-based materials such as Pb(Zr,Ti)O₃ (PZT) for high-power applications. This review focuses on three prominent lead-free ceramic systems: BaTiO₃ (BT), Bi_0.5Na_0.5TiO₃ (BNT), and (Na_0.5K_0.5)NbO₃ (NKN). BT-based ceramics offer excellent piezoelectric properties but are limited by their low Curie temperatures, which has been addressed through doping and sintering aids such as Li₂O. BNT-based ceramics exhibit high thermal stabilities and tunable electromechanical properties; however, challenges remain because of their relatively low piezoelectric coefficients. NKN-based ceramics demonstrate outstanding mechanical quality factors (Q_m) and high Curie temperatures, with significant performance improvements achieved through CuO doping and co-doping with other oxides. Despite these advancements, issues such as thermal stability, alkaline element volatility, and limited d₃₃ still need to be resolved. Continued progress in doping strategies, microstructural control, and advanced processing techniques will be crucial to fully unlock the potential of lead-free piezoelectric ceramics for high-power applications.