Direct observation of oxygen stabilization in layered ferroelectric Bi3.25La0.75Ti3O12

Abstract

Electron charge density distributions in layered ferroelectrics Bi4Ti3O12 (BiT) and Bi3.25La0.75Ti3O12 (BLT) are investigated by analyzing high-energy synchrotron-radiation powder diffraction data using the maximum entropy method/Rietveld method. BiT shows that chemical bonding resulting from orbital hybridization is established between Bi–O in the perovskite layer only along the a axis, whereas BLT exhibits isotropic chemical bonding of Bi∕La–O with a high electron density both along the a and b axes. High endurance to polarization fatigue reported for BLT films is suggested to originate from the stabilization of oxygen in the perovskite layer due to the isotropic chemical bonding of Bi∕La–O.