High-temperature behaviour of the CuMo₃O₁₀ ⋅ H₂O compound

Ismagilova R. M., Zhitova E. S., Zolotarev A. A., Shilovskikh V. V.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2021. V. 150. N 2. P. 92-105

https://doi.org/10.31857/S0869605521020076

Full text is available on eLIBRARY.RU

Language: Russian 

Abstract

CuMo₃O₁₀ ⋅ H₂O crystals have been obtained by hydrothermal synthesis as a result of reaction between (NH₄)₆Mo₇O₂₄ ⋅ 4H₂O and Cu(CH₃COO)₂ at 220 °C during 7 days. The Xray powder diffraction data in wide range of temperature have shown that the studied phase is stable within the range from –180 to 300 °С. Its thermal expansion is anisotropic, thermal expansion coefficients, calculated at Т = 100 °С, are: α_a = 28.5, α_b = 6.1 and α_c = 13.3 °С–1. Structural changes have been analyzed by the structure refinement method based on the single-crystal X-ray diffraction data at different temperatures. Thermal expansion anisotropy is connected with the chain-structure type and the angle deformations caused by changes in inter-atomic angles in the CuO₆ octahedra and in inter-polyhedral angles between copper octahedron and trimolybdate chains. The high-temperature behavior of CuMo₃O₁₀ ⋅ H₂O is compared in the paper with behavior of chemically close copper molybdates – lindgrenite, szenicsite and cupromolybdate.

Keywords: copper and molybdenum compounds, trimolybdates, thermal expansion, dynamics of crystal structure