X-Ray and Mössbauer Studies in the Sr(FeTa)_1⁄2O₃ and Sr(CrTa)_1⁄2O₃ System

Abstract

Sr(FeTa)_1⁄2O₃ is a disordered perovskite, tetragonal at room temperature, while Sr(CrTa)_1⁄2O₃ is an ordered perovskite, cubic at room temperature. These compounds make solid solutions in the whole range of composition. Tetragonal-cubic transition occurs at about 90 mol% of Sr(FeTa)_1⁄2O₃. Intensity of superstructure line of X-ray diffraction which shows the ordered arrangement of the B ions decreases gradually with increase of Sr(FeTa)_1⁄2O₃. Isomer shift is nearly constant, 0.64 mm/sec, for all compounds, the value of which is reasonable for Fe³⁺. The curve of the quadrupole splitting vs composition is rather complicated. We can give it a qualitative interpratation in terms of local distortion arising from the disordered distribution of the Ta, xFe and (1−x)Cr ions.