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 P2(1)/n (no. 14); for M = Mo, a = 5.76228(7), b = 5.84790(7), c = 8.18707(9) Angstrom, beta = 90.194(1)degrees, for M = Te, a = 5.79919(9), b = 5.83756(8),, = 8.2175(1) Angstrom, beta = 90.194(1)degrees). 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. (C) 2004 Elsevier Inc. All rights reserved.