Synthesis, Structure, and Thermal Expansion of BiCr 2 (PO 4 ) 3 , SbCr 2 (PO 4 ) 3 , and Bi 1– x Sb х Cr 2 (PO 4 ) 3 Solid Solution

Samples of the Bi 1– x Sb х Cr 2 (PO 4 ) 3 system with the structure of α-CaMg 2 (SO 4 ) 3 were obtained by evaporation of a solution of salts with subsequent heat treatment, and characterized. Refinement of the BiCr 2 (PO 4 ) 3 ( x = 0) and SbCr 2 (PO 4 ) 3 ( x = 1) structures by the Rietveld method showed that the [Cr 2 (PO 4 ) 3 ] 3∞ framework is formed by CrO 6 octahedra doubled by faces, between which PO 4 tetrahedra attached to the octahedra by oxygen vertices are located, the voids of the framework are populated by six coordinated bismuth or antimony atoms. By varying the composition of the unlimited solid solution Bi 1– x Sb х Cr 2 (PO 4 ) 3 , it is possible to obtain materials with low thermal expansion coefficients: 0.5×10 −6 ≤ α av ≤ 1.9×10 −6 °C −1 .