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-di mensional lattice of the perovskite-type oxide La1-xSrxCuO3 (0 less th an or equal to x less than or equal to 0.25). Chemical analysis and XP S studies confirm the mixed valence. This compound shows metallic prop erties with a broadening of the conduction band compared to that of La CuO3. Such behavior can be explained either by the increase of the cov alence of the average Cu-O bond or by the decrease of the structural d istortion induced by the substitution of Sr(II) for La(III). No superc onducting property has been detected in the material to temperatures a s low as 4 K. (C) 1995 Academic Press, Inc.