Enhanced Temperature Stability and Defect Mechanism of BNT-Based Lead-Free Piezoceramics Investigated by a Quenching Process

Because of the environmental concerns of eliminating lead from piezoelectric products, bismuth-based perovskite is becoming one of the most potential candidates. However, its relatively low thermal depolarization temperature (T-d) is still an imperative obstacle hindering implementation of this material for practical application. Here, an enhanced temperature stability of 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO(3) (BNTBT6) piezoceramics is reported, which can be obtained by the effective quenching process. Quenching process enhances the depolarization temperature to 136 degrees C, which is 40 degrees C higher than that of normal sintered samples. By using X-ray photoelectron spectroscopy and electron paramagnetic resonance methods, it is revealed that oxygen vacancy may exist in the quenched samples and consequently pins the domain walls, resulting in significant enhancement of depolarization temperature. Temperature-dependent dielectric, piezoelectric, and ferroelectric behaviors are measured as criteria to evidence the enhanced temperature stability.