Lattice distortion-induced ferroelectricity in nonstoichiometric Ba-0.9(Fe0.5Nb0.5)O-3- d thin films

Transforming materials from paraelectric state to ferroelectric state provides a tremendous opportunity to increase the variety of ferroelectric materials, but it remains a big challenge. Herein, A-site nonstoichiometric defects are artificially designed in Ba-0.9(Fe0.5Nb0.5)O-3- (delta) thin film, resulting in the appearance of lattice distortion and ferroelectric state. Tetragonal distortion and partial dislocation are introduced so as to benefit the symmetry breaking and promote spontaneous polarization. Robust ferroelectricity at room temperature with a remanent polarization around 8 mu C cm(-2) and a high phase stability temperature up to 450 degrees C are successfully achieved. Our work proposes a practical approach for discovering and regulating new ferroelectric materials through defect engineering.