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| Home > Publications database > Temperature and doping induced evolution of the local structure of thermochromic copper molybdate |
| Poster | PUBDB-2019-03592 |
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2019
Abstract: Copper molybdate (CuMoO4) has been intensively studied due to its diverse functional properties, including thermochromic, piezochromic, tribochromic, photoelectrochemical as well as catalytic and antibacterial. At room temperature and atmospheric pressure CuMoO4 exists in alpha phase with a bright green colour. Its structure is composed of distorted CuO6 octahedra, CuO5 square-pyramids and MoO4 tetrahedra. By applying pressure or decreasing temperature below ~200 K, copper molybdate colour changes to brownish-red due to the first order phase transition from alpha to gamma phase. The gamma phase is built up of distorted CuO6 and MoO6 octahedra. It is possible to affect the p-T diagram of CuMoO4 and, thus, its properties, by a substitution of Cu2+ ions with other divalent ions as Zn2+ or a substitution of Mo6+ with W6+. Note that similar colour change from green to brown occurs in alpha phase upon heating up to about 673 K. In this study, we use X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) to investigate the relationship between structural effects and optical properties of copper molybdate and its solid solutions with tungsten in the wide temperature range from 10 K up to 973 K. While treatment of thermal fluctuations and static disorder in XAS is a complex task, it can be successfully addressed by reverse Monte Carlo (RMC) simulations.
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