Ferroelectric distortion and electronic structure in Bi4Ti3O12

The ferroelectric phase transition in Bi4Ti3O12 has been investigated through Rietveld analysis of high-resolution neutron powder diffraction and electronic structure calculations. The structural and electronic analyses show that the traditional model based on the stereoactive lone-pair 6.s electrons of Bi3+ is not sufficient to explain the structural distortions in the ferroelectric state. It is strongly suggested that the hybridization of the Bi 6p and the O 2p in the perovskite layers is the trigger of the ferroelectric transition in Bi4Ti3O12, and that this orbital interaction is responsible for stabilizing the ferroelectric displacements in the perovskite layers.