Crystal Structure of the Monoclinic Perovskite Sr3.94Cad1.31^Bi2.70O12

Published

December 1, 2000

Author(s)

Winnie K. Wong-Ng, James A. Kaduk, Qingzhen Huang, Robert S. Roth

Abstract

The crystal structure of the low temperature oxidized form of Sr_3.94Ca_1.31Bi_2.70O₁₂ has been determined using a combined Rietveld refinement technique with neutron, synchrotron, and powder x-ray diffraction data. The structure is pseudo-orthorhombic, and systematic absences indicated the structure to be monoclinic with space group P2₁/n. Final refinement using neutron diffraction gives the lattice parameters of a = 8.38931(16) , b = 5.99445(11) , c = 5.89572(11) ,= 89.961(3), and V = 296.49(1) ³. This is a distorted pervoskite phase (described in the perovskite ABO₃ formula as Sr(Bi_0.67Ca_0.33)O₃ ) with 1:1 ordering of the M-site cations with formula A₂MM'O₆. The MO₆ and M'O₆ octahedra connected to each other via corner-sharing, and are tilted with respect to the neighboring layers with an angle of 15 around all three axis. The tilt system symbol is a⁺a^-a^- according to Glazer notation. All Bi ions are in 5+ oxidation state. In this 1:1 ordered structure, the A sites are solely occupied by Sr, the M sites mainly by Bi (doped with 2% of Ca), while in the M' sites Bi and Ca are distributed in an approximate ratio of 3:2.

Citation

Powder Diffraction

Volume

15 No. 4

Pub Type

Journals

Keywords

BSCCO system, CaO₃, low-temperature form, perovskite, SrCBi, structure

Citation

Wong-Ng, W. , A., J. , Huang, Q. and Roth, R. (2000), Crystal Structure of the Monoclinic Perovskite Sr_3.94Cad1.31^Bi_2.70O₁₂, Powder Diffraction (Accessed October 8, 2024)