Temperature-Driven Structural Phase Transition in Tetragonal-Like BiFeO3

Highly strained BiFeO3 exhibits a tetragonal-like, monoclinic crystal structure found only in epitaxial films (with an out-of-plane lattice parameter exceeding the in-plane value by > 20%). Previous work has shown that this phase is properly described as an M-C monoclinic structure at room temperature [with a (010)(pc) symmetry plane, which contains the ferroelectric polarization]. Here, we show detailed temperature-dependent X-ray diffraction data that reveal a structural phase transition at similar to 100 degrees C to a high-temperature M-A phase [tetragonal-like but with a ((1) over bar 10)(pc) symmetry plane]. These results indicate that the ferroelectric properties and domain structures of the strained BiFeO3 are strongly temperature dependent. (C) 2011 The Japan Society of Applied Physics