A STUDY OF THE OXYGEN-DEFICIENT PEROVSKITE SYSTEM SR2FE2-XCRXO5+Y BY MOSSBAUER-SPECTROSCOPY

The oxygen-deficient perovskite system Sr2Fe2-xCrxO5+y (x = 0.5, 0.67, 1.0) has been studied by Mössbauer spectroscopy and X-ray powder diffraction techniques. The material obtained is strongly dependent upon the conditions of preparation, although the iron is usually present as Fe3+. The system as a whole is more strongly oxidized than the calcium analogue, from which it differs considerably, and significant amounts of Sr3Cr2O8 and SrCrO4 may be formed in air. Several single-phase perovskite-related compounds have been observed. Most significant of these is a rhombohedral 15R-phase with a large unit cell, the nature of which is uncertain. Evidence was also found for an orthorhombic perovskite which is probably the n = 5 2 member of the AnBnO3n-1 series. A number of cubic phases have been prepared. Mössbauer spectroscopy has been used to characterize the iron site environments and magnetic behavior of these materials. © 1990.