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

Published

August 16, 1999

Author(s)

Winnie K. Wong-Ng, James A. Kaduk, R A. Young, F Jiang

Abstract

The structures of the solid solution series (Sr_4-δCa_δ)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 Sr_3.15Ca_0.85PtO₆. 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

Pub Type

Journals

Keywords

(Sr4-8Cas) PtO6, crystallography, reference x-ray patterns, Rietveld refinement, solid solutions, x-ray diffraction

Citation

Wong-Ng, W. , A., J. , Young, R. and Jiang, F. (1999), Structural investigation of (Sr_4-δCa_δ)PtO₆ Using X-Ray Rietveld Refinement, Powder Diffraction (Accessed April 18, 2024)