High electrostrictive properties and energy storage performances with excellent thermal stability in Nb-doped...

As a promising candidate material replacing Pb(ZrTi)O₃ (PZT), the lead-free Bi_0.5Na_0.5TiO₃ (BNT) system exhibits outstanding piezoelectric and ferroelectric properties. However, the weak thermal stability of these electric properties hampers its practical applications. In this work, we designed and prepared novel Nb-doped 0.76Bi_0.5Na_0.5TiO₃-0.24Bi_0.5K_0.5TiO₃ (BNT-BKT) ceramics with superior temperature stability of electric properties. Both strain as well as discharging properties of 5% Nb-doped BNT-BKT ceramics varied less than 3% and 12.5% respectively from room temperature to 160 °C, ascribed to the enlarged gap between the depolarized temperature (T _d or T _F-R) and the maximum dielectric temperature (T _m). In addition, we investigated the impacts of Nb doping on the phase transition, dielectric, piezoelectric and ferroelectric behaviors of BNT-BKT ceramics in detail. Temperature dependent dielectric spectrums indicated that T _d decreased below room temperature with Nb modifying, revealing that the phase structure transformed from ferroelectric into ergodic relaxor. Accordingly, the maximum strain value of 0.21% and recoverable energy storage of 1.2 J cm^-3 were simultaneously acquired at the critical composition of 5% Nb incorporation. Our results provide an effective means of obtaining BNT-based ceramics with simultaneously thermally stable strain and discharge properties for wide temperature actuator and capacitor applications.