Structure evolution and ferroelectric properties in stoichiometric Bi0.5+xNa0.5−xTi1−0.5xO3

The influence of B-site deficiency on the stability of electrically induced long-range ferroelectric order of the stoichiometric Bi_0.5+xNa_0.5−xTi_1−0.5x□_0.5xO₃ (BNT-xV_Ti) (“□” denotes vacancies) ceramics is studied. The depolarization and ferroelectric to relaxor transition are identified as separate and discrete processes in BNT-based materials. For BNT-0.02V_Ti, the resonance and anti-resonance peaks on dielectric permittivity-frequency curves indicate dominating ferroelectric phase at room temperature. The depolarization temperature, determined by thermally stimulated depolarization current, is ~ 65 °C. However, the ferroelectric to relaxor transition temperature is absent, as no distinct frequency-independent anomalies for the dielectric permittivity exist. This depolarization process can be ascribed to nanoscale ferroelectric domain at room temperature for BNT-0.02V_Ti, which is induced by chemical disorder and strong random field as V_Ti generated. Hence, the results imply that the B-site deficiency in BNT is a very effective route to tailor the stability of electrically induced long-range ferroelectric order.