Structural chemistry of the cation-ordered perovskites Sr2CaMo1−xTexO6 (0⩽x⩽1)

The crystal structures of Sr2CaMoO6 and Sr2CaTeO6 have been determined at room temperature by neutron powder diffraction. Both compounds crystallize in the perovskite structure with a rock-salt ordered array of Ca2+ and M6+ cations (M=Mo, Te) on the six-coordinate sites (space group P21/n (no. 14); for M=Mo, image, image, image, image, for M=Te, image, image, image, image). Compositions in the solid solution Sr2CaMo1−xTexO6 have been synthesized and shown by X-ray diffraction to adopt the same ordered structure. The results are used in a discussion of the cation oxidation states in Ca2FeMoO6 and to establish the similarity between the structural chemistry of hexavalent Mo and Te.