Characterization of crystal structure, electrical and electromechanical properties of Mg-doped 0.94Na_1/2Bi_1/2TiO₃-0.06BaTiO₃

The use of lead-free piezoelectric materials in high-power applications requires a high mechanical quality factor Q_m and temperature-stable ferroelectric properties. In this article, the influence of Mg-doping on the 0.94Na_1/2Bi_1/2TiO₃-0.06BaTiO₃ system is analysed with focus on the role of defects related to ferroelectric hardening. Temperature stability (depolarization temperature), electromechanical properties (piezoelectric activity, Q_m), electrical properties (conductivity) and crystal structure for compositions were quantified. Compositions with similar amount of Zn-doping were analyzed for reference. A drastic increase in electrical conductivity at −0.3/−0.5 mol% Mg was associated with a concomitant increase in Q_m. Similar behavior in Zn-doped compositions provides a basis for a more comprehensive mechanistic understanding of acceptor doping in these lead-free piezoceramics. The very high and almost vibration-velocity-independent Q_m above 800 makes Mg-doped 0.94Na_1/2Bi_1/2TiO₃-0.06BaTiO₃ an excellent candidate for high-power application.