Temperature-dependent high energy-resolution EELS of ferroelectric and paraelectricBaTiO3phases

Abstract

Probing the ferroelectricity at the nanometer scale is of particular interest for a wide range of applications. In this Rapid Communication, the structural distortion of ${\mathrm{BaTiO}}_{3}$ (BTO) is studied in its ferroelectric (rhombohedral and tetragonal), and paraelectric phases from the O $K$ near edge structures in electron energy loss spectroscopy. Modifications of the electronic structure are detected in the lowest energy fine structure (FS) of the O $K$ edge in the ferroelectric phases, and are interpreted by core-hole valence-electron screening geometry. For the paraelectric phase, the lowest energy FS of the O $K$ edge is comparable to the one obtained at room temperature, which is inconsistent with an expected cubic structure. The variations observed in the O $K$ near edge structures, such as a broader and more asymmetric lowest energy FS at low temperature, suggest that the magnitude of the $\mathrm{Ti}^{4+}$ off-centering along $\ensuremath{\langle}111\ensuremath{\rangle}$ increases in lower-temperature phases. These findings demonstrate the sensitivity of the O $K$ near edge structures to the structural distortions of BTO polymorphs, and form a basis for further investigations on defective or strained BTO at the nanoscale.