Acta Crystallographica Section C

Crystal Structure Communications

Volume 64, Part 8 (August 2008)

inorganic compounds

Acta Cryst. (2008). C64, i71-i72 [ doi:10.1107/S0108270108021045 ]

A new bismuth iron oxyphosphate, Bi₆(Bi_0.32Fe_0.68)(PO₄)₄O₄

N. Arumugam, V. Lynch and H. Steinfink

Abstract: Iron was inserted into the known crystal structure of the bismuth phosphate oxide Bi_6.67(PO₄)₄O₄ to ascertain its location in the vacancies associated with the bismuth ion located at the origin of the unit cell. Single-crystal X-ray diffraction refinements converged to a model of composition Bi₆(Bi_0.32Fe_0.68)(PO₄)₄O₄ (hexabismuth iron tetraphosphate tetraoxide), in which Bi and Fe are displaced from the origin giving rise to a random distribution over the 2i sites instead of 1a, the origin of space group P $\overline{1}$ . The isotropic displacement parameter for Bi/Fe has a reasonable value in this model. This structure establishes for the first time that Fe substitutes in the Bi-deficient site in this series of materials and that Fe and Bi are disordered around the center of symmetry. These results enhance understanding of the crystal chemistry of these main group phosphates that are of interest in ion transport.

Formula: Bi₆(Bi_0.32Fe_0.68)(PO₄)₄O₄