Study of the thermochromic phase transition in CuMoWO solid solutions at the W L-edge by resonant X-ray emission spectroscopy
arXiv:2012.15217 · doi:10.1016/j.actamat.2020.116581
Abstract
Polycrystalline CuMoWO solid solutions were studied by resonant X-ray emission spectroscopy (RXES) at the W L-edge to follow a variation of the tungsten local atomic and electronic structures across thermochromic phase transition as a function of sample composition and temperature. The experimental results were interpreted using ab initio calculations. The crystal-field splitting parameter for the 5d(W)-states was obtained from the analysis of the RXES plane and was used to evaluate the coordination of tungsten atoms. Temperature-dependent RXES measurements were successfully employed to determine the hysteretic behaviour of the structural phase transition between the and phases in CuMoWO solid solutions on cooling and heating, even at low (<0.10) tungsten content. It was found that tungsten ions have octahedral coordination for in the whole studied temperature range (90-420 K), whereas their coordination changes from tetrahedral to octahedral upon cooling for smaller ( <= 0.15) tungsten content. Nevertheless, some amount of tungsten ions was found to co-exists in the octahedral environment at room temperature for <0.15. The obtained results correlate well with the color change in these solid solutions.