Characterization of Lanthanum(III) Chromium(V) Tetraoxide by X-Ray Photoelectron Spectroscopy

Abstract

Lanthanum(III) chromium(V) tetraoxide, LaCrO₄, was synthesized by a thermal decomposition method and characterized by X-ray photoelectron spectroscopy and ab initio molecular orbital calculations. The chromium(V) state in LaCrO₄ is stable in both air and vacuum. The electron binding energies, E_B, and Auger parameters, α, of Cr(V) and La(III) indicated that the covalency of the Cr-O bonds in CrO₄ tetrahedra is higher than that in CrO₆ octahedra of LaCrO₃, and that La(III) in LaCrO₄ is more ionic than in LaCrO₃. The results of ab initio molecular orbital calculations agreed with the measured characteristics, that is, the electrons are flowing from oxygen to Cr(V) and the covalency plays a significant part in the Cr-O bonds. This behavior of the Cr-O bond was considered to contribute to stabilizing CrO₄^3- tetrahedra.