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Publication Citation: Structural investigation of (Sr4-δCaδ)PtO6 Using X-Ray Rietveld Refinement

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Author(s): Winnie K. Wong-Ng; James A. Kaduk; R A. Young; F Jiang;
Title: Structural investigation of (Sr4-δCaδ)PtO6 Using X-Ray Rietveld Refinement
Published: August 16, 1999
Abstract: The structures of the solid solution series (Sr4-δCaδ)PtO6, with δ = 0, 0.85(1), 2, and 3, have been investigated using the Rietveld refinement technique with laboratory x-ray powder data. A complete solid solution between Sr and Ca was confirmed to exist. These compounds crystallize in the rhombohedral space R3c. The cell parameters of the series range from a of 9.4780(3) {Angstrom} to 9.7477(1) {Angstrom}, and c from 11.3301(4) {Angstrom} to 11.8791(1) {Angstrom} for δ from 3 to 0, respectively. The structure consists of chains of alternating trigonal prismatic (Sr, Ca)O6 and octahedral PtO6 units running parallel to the c-axis. These chains are connected to each other via a second type of (Sr,Ca) ions, which are surrounded by eight oxygens, in a distorted square antiprismatic geometry. As Ca replaced Sr in Sr4PtO6, it was found to substitute preferentially in the smaller octahedral (Sr,Ca)1 site (6a) rather than at the 8-coordiante (Sr,Ca)2 site (18e). There appears to be an anomaly of cell parameters a and c at the compound Sr3.15Ca0.85PtO6. Their dependence on Ca content changes at δ {approximately equal to} 1.00, where the Ca has fully replaced Sr in the 6a site. The substitution of Sr by Ca reduced the average (Sr,Ca)1-O length from 2.411 {Angstrom} to 2.311 {Angstrom} and (Sr,Ca)2-O from 2.659 {Angstrom} to 2.570 {Angstrom} as the composition varied from Sr4PtO6 to SrCa3PtO6. Reference x-ray powder diffraction patterns were prepared from the Rietveld refinement results for these members of the solid solution series.
Citation: Powder Diffraction
Volume: 14
Issue: 3
Pages: pp. 181 - 181
Keywords: (Sr4-8Cas) PtO6,crystallography,reference x-ray patterns,Rietveld refinement,solid solutions,x-ray diffraction
Research Areas: Ceramics, Materials Science