In-situ high temperature Raman spectroscopic study on the structural evolution of Na₂W₂O₇ from the crystalline to molten states

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• 作者：J. Wang ; J. L. You ; A. A. Sobol ; L. M. Lu ; M. Wang ; J. Wu ; X. M. Lv and S. M. Wan
• 刊名：Journal of Raman Spectroscopy
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：48
• 期：2
• 页码：298-304
• 全文大小：801K
• ISSN：1097-4555

文摘

In order to optimize the growth conditions for tungstate crystals, the structural evolution of ditungstate Na₂W₂O₇ from the crystalline to molten states during heating has been investigated by in-situ high temperature Raman spectroscopic technique. The experimental temperature-dependent Raman spectra showed that Na₂W₂O₇ crystal has not undergone any solid-state phase transformations during heating process from 298 to 1013 K. In contrast to crystalline Na₂W₂O₇, in which [WO₄] tetrahedra and [WO₆] octahedra coexist, the tungsten–oxygen groups in molten Na₂W₂O₇ have the form of (W₂O₇)²⁻ anion composed of two [WO₄] by sharing their corner oxygen atoms. To validate the structural evolution of Na₂W₂O₇ above, Raman activity of vibrations of Na₂W₂O₇ crystal and its melt were calculated using density functional theory (DFT) and compared with the in-situ Raman spectra of Na₂W₂O₇. A non-crystalline phase and an intermediate state of Na₂W₂O₇ were obtained by rapid quenching and relatively slow cooling of the homogeneous melt, respectively. Copyright