用共振X射线发射光谱研究CuMo $_{1-x}$ W $_x$ O $_4$固溶体在W L $_3$边的热致变色相变
Study of the thermochromic phase transition in CuMo$_{1-x}$W$_x$O$_4$ solid solutions at the W L$_3$-edge by resonant X-ray emission spectroscopy
摘要：
多晶CuMo $_{1-x}$ W $_x$ O $_4$固溶体进行了研究，通过共振X射线发射光谱（RXES）在W L $_3$ -边缘，以遵循作为样品组成和温度的函数的跨热致变色相变的钨局部原子和电子结构的变化。用从头计算对实验结果进行了解释。通过对RXES平面的分析，得到了5d（W）态的晶场分裂参数，并用于评价钨原子的配位。温度依赖的RXES测量成功地用于确定在冷却和加热时CuMo $_{1-x}$ W $_x$ O $_4$固溶体中的$α$和$γ$相之间的结构相变的滞后行为，即使在低（$x$ <0.10）钨含量下。结果表明，在90-420 K的温度范围内，钨离子均为八面体配位，而当钨含量较低（$x$ <= 0.15）时，钨离子的配位随温度的降低由四面体变为八面体。然而，对于$x$ <0.15，在室温下发现一定量的钨离子共存于八面体环境中。所得结果与这些固溶体中的颜色变化很好地相关。
英文摘要：
Polycrystalline CuMo$_{1-x}$W$_x$O$_4$ solid solutions were studied by resonant X-ray emission spectroscopy (RXES) at the W L$_3$-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 $α$ and $γ$ phases in CuMo$_{1-x}$W$_x$O$_4$ solid solutions on cooling and heating, even at low ($x$<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 ($x$ <= 0.15) tungsten content. Nevertheless, some amount of tungsten ions was found to co-exists in the octahedral environment at room temperature for $x$<0.15. The obtained results correlate well with the color change in these solid solutions.
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