Abstract
AbstractIn this work, 0.8Na0.5Bi0.5TiO3‐0.2K0.5Bi0.5TiO3 (BNKT) is studied by electrical characterizations, in situ Raman spectra in conjunction with the phenomenological Landau predictions to reveal the local phenomena. An electric field‐induced nonergodic relaxor‐to‐ferroelectric phase transition and domain switching start to take place at a critical field of 3 kV/mm. The polar phase was disrupted into the disordered relaxor phase at ferroelectric‐relaxor transition temperature (TFR) along with the discontinuous phonon anomalies caused by the decoupling between the off‐centered Bi and Ti cations. The R3c and P4bm polar nanoregions (PNRs) can coexist in a wide temperature range and can be transformed reversibly below the temperature of dielectric maximum (Tm). The broad Raman bands were found to persist in high‐temperature paraelectric state induced by the existence of off‐centered Ti cation and ferroically deformed TiO6 octahedra. A phenomenological Landau model and local structural evolution sequence at different thermal history were proposed to further elucidate the underlying mechanisms. This work will be conducive to understanding the local structure‐physical property correlations of high‐performance lead‐free piezoelectrics.
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