Crystal structures and reference x-ray powder diffraction patterns of Sr4-xCaxPb2O8 (x=1,2,3)

The crystal structure of the solid solution alkaline earth plumbate phase S r4-xCaxPb2O8 was investigated using the X-ray Rietveld technique for x = 1, 2, and 3. The lattice parameters a, b, c, and V were found to decrease lin early as the Sr at site 4h was replaced by Ca. The structure features chain s of edge-sharing PbO6 octahedra, linked by seven-coordinated (Ca/Sr)-O mon ocapped trigonal prisms. The structure is similar to that of Pb3O4, which c an be reformulated as (Pb2PbO4)-Pb-II-O-IV. X-ray diffraction patterns for the solid solution members SrCa3Pb2O8, Sr2Ca2Pb2O8, and Sr3CaPb2O8 were pre pared for inclusion in the Powder Diffraction File. (C) 1998 International Centre for Diffraction Data. [S0885-7156(98)00402-3].