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 formu la Sr(Sr0.5Sb0.5)O3-y has been synthesized readily by a solid state reactio n in air at 1200 degreesC. The structure of the Sr(Sr0.5Sb0.5)O3-y phase as determined by Rietveld analysis using X-ray diffraction data, corresponds to an ordered perovskite with face-centered cubic symmetry, space group Fm3 m (no. 225) and lattice parameters, a = 8.3136(3) Angstrom, V = 574.602(3) Angstrom (3) and Z = 8. An important structural feature of Sr(Sr0.5Sb0.5)O3 -y is the oxygen deficiency and the displacements of oxygen atoms from thei r ideal positions toward the Sb5+ cations. This fact leads to an alternatin g arrangement of larger [SrO6] and smaller [SbO6] octahedra (B-sites), the remaining Sr2+ being in the larger 12-fold coordinated A-sites. The thermal stability of the Sr(Sr0.5Sb0.5)O3-y phase is pointed out, its melting poin t being 1480 degreesC, and the subsequent quenching giving rise to a glass material. (C) 2001 Elsevier Science Ltd. All rights reserved.