STABILIZATION OF THE MIXED-VALENCE CU(III) CU(IV) IN THE PEROVSKITE LATTICE OF LA1-XSRXCUO3 UNDER HIGH OXYGEN-PRESSURE

A new mixed valence Cu(III)/Cu(IV) has been stabilized in the three-dimensional lattice of the perovskite-type oxide La1-xSrxCuO3 (0 less than or equal to x less than or equal to 0.25). Chemical analysis and XPS studies confirm the mixed valence. This compound shows metallic properties with a broadening of the conduction band compared to that of LaCuO3. Such behavior can be explained either by the increase of the covalence of the average Cu-O bond or by the decrease of the structural distortion induced by the substitution of Sr(II) for La(III). No superconducting property has been detected in the material to temperatures as low as 4 K. (C) 1995 Academic Press, Inc.