Oxygen deficiency and formation of a new ordered perovskite-based structure Sr(Sr0.5Sb0.5)O3−y

A new oxygen-deficient and ordered perovskite-type structure with the formula Sr(Sr 0.5 Sb 0.5 )O 3− y has been synthesized readily by a solid state reaction in air at 1200°C. The structure of the Sr(Sr 0.5 Sb 0.5 )O 3− y phase as determined by Rietveld analysis using X-ray diffraction data, corresponds to an ordered perovskite with face-centered cubic symmetry, space group Fm 3 m (no. 225) and lattice parameters, a =8.3136(3) A, V =574.602(3) A 3 and Z =8. An important structural feature of Sr(Sr 0.5 Sb 0.5 )O 3− y is the oxygen deficiency and the displacements of oxygen atoms from their ideal positions toward the Sb 5+ cations. This fact leads to an alternating arrangement of larger [SrO 6 ] and smaller [SbO 6 ] octahedra (B-sites), the remaining Sr 2+ being in the larger 12-fold coordinated A-sites. The thermal stability of the Sr(Sr 0.5 Sb 0.5 )O 3− y phase is pointed out, its melting point being 1480°C, and the subsequent quenching giving rise to a glass material.