Synthesis, structure, and thermal expansion of BiCr<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>, SbCr<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> and Bi<sub><sub>1-</sub><sub><i>x</i></sub></sub>Sb<sub><i>х</i></sub>Cr<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> solid solutions

Abstract

The manifestations of the Bi1- x Sb x Cr2(PO4)3 system with the α-CaMg2(SO4)3 structure were obtained and characterized by the evaporation of salt solutions with heat treatment. Refinement of the Rietveld method for the structure of BiCr2(PO4)3 ( x = 0) and SbCr2(PO4)3 ( x = 1) showed that the [Cr2(PO4)3]3∞ framework is formed by CrO6 octahedra doubled by faces, PO4 tetrahedra are between the dependences, attached to the octahedrons by oxygen vertices, the voids of the framework are populated by six-coordinated bismuth or antimony atoms. By varying the composition of the Bi1- x Sb x Cr2(PO4)3 solid solution everywhere, it is possible to obtain materials with low thermal expansion coefficients: 0.5×10-6 ≤ α av ≤ 1.9×10-6 °C-1.