CHARACTERIZATION OF LANTHANUM(III) CHROMIUM(V) TETRAOXIDE BY X-RAY PHOTOELECTRON-SPECTROSCOPY

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, alpha, 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 CrO43-tetrahedra.