X-RAY PHOTOELECTRON SPECTROSCOPY STUDY OF La<SUB>1-x</SUB>Sr<SUB>x</SUB>CoO<SUB>3</SUB>

La(1-x)Sr(x)CoO(3) has been studied by XPS. It is showed that the La 3d(5/2) spectrum is a doublet. The peak of higher one of BE is assigned to a shake-up satellite, which results from that 2p electrons of oxygen transfer to the empty 4f orbital of lanthanum. The ratio R of the intensity of shake up satellite to parent peak is a measure of covalency of La-O.R, and hence the covalency of La-O increases with the increasing stronium content, The R is called COVALENT FACTOR. It was In that if stronium was partly substituted for the place of lanthanum, it would influence the covalency of La-O. The covaleney of Co-O decreases with the increase of stronium content, while ionicity of Co-O increases, which results in a change of reducing temperature of cobalt in La(1-x)Sr(x)CoO(3). We succeeded in explaining the reasons of both segregation. of lanthanum of LaCoO(3) and no segregation when stronium was partly substituted for the place of lanthanum.