Structure evolution and ferroelectric properties in stoichiometric Bi0.5+xNa0.5−xTi1−0.5xO3
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The influence of B-site deficiency on the stability of electrically induced long-range ferroelectric order of the stoichiometric Bi0.5+xNa0.5−xTi1−0.5x□0.5xO3 (BNT-xVTi) (“□” 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-0.02VTi, 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-0.02VTi, which is induced by chemical disorder and strong random field as VTi 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.
This work was supported by the National Natural Science Foundation (51702249, 51602252), the China Postdoctoral Science Foundation (2017M613065) and the Shaanxi Province Science Foundation (2017JQ5072).