Electronic state of nickel in barium nickel oxide, BaNiO3

An attempt is made to draw conclusions on the binding situation and the electronic state of nickel in the hexagonal perovskite BaNiO3 characterized by chain units of face sharing NiO6 octahedra by means of XPS, IR, and Mossbauer spectroscopy and susceptibility measurements. Although the results of Mossbauer measurements appear to favor the existence of quadrivalent Ni, the photoelectron spectroscopy data suggest the description of BaNiO3 in terms of trivalent Ni and oxygen anion holes. In terms of a local ionic model the idealized description of this high-valent oxometalate would correspond to Ba2+Ni3+(O-2)(2)O.-. A binding model was formulated by taking into account the structural and electronic properties of the compound.