Crystal Structure of the Monoclinic Perovskite Sr3.94Cad1.31^Bi2.70O12
Winnie K. Wong-Ng, James A. Kaduk, Qingzhen Huang, Robert S. Roth
The crystal structure of the low temperature oxidized form of Sr3.94Ca1.31Bi2.70O12 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(Bi0.67Ca0.33)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.
, A., J.
, Huang, Q.
and Roth, R.
Crystal Structure of the Monoclinic Perovskite Sr<sub>3.94Ca</sub>d1.31^Bi<sub>2.70</sub>O<sub>12</sub>, Powder Diffraction
(Accessed December 11, 2023)