Tellurium Speciation, Connectivity, and Chemical Order in AsxTe100鈥?i>x Glasses: Results from Two-Dimensional 125Te NMR Spectroscopy

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• 作者：Derrick C. Kaseman ; Ivan Hung ; Kathleen Lee ; Kirill Kovnir ; Zhehong Gan ; Bruce Aitken ; Sabyasachi Sen
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：February 5, 2015
• 年：2015
• 卷：119
• 期：5
• 页码：2081-2088
• 全文大小：411K
• ISSN：1520-5207

文摘

The short-range structure, connectivity, and chemical order in As_xTe_100鈥?i>x (25 鈮?x 鈮?65) glasses are studied using high-resolution two-dimensional projection magic-angle-turning (pjMAT) ¹²⁵Te nuclear magnetic resonance (NMR) spectroscopy. The ¹²⁵Te pjMAT NMR results indicate that the coordination of Te atoms obeys the 8鈥?i>N coordination rule over the entire composition range. However, in strong contrast with the analogous glass-forming As鈥揝 and As鈥揝e chalcogenides, significant violation of chemical order is observed in As鈥揟e glasses over the entire composition range in the form of homopolar As鈥揂s (Te鈥揟e) bonds, even in severely As聽(Te)-deficient glasses. The speciation of the Te coordination environments can be explained with the dissociation reaction model As₂Te₃ 鈫?2As + 3Te^II, characterized by a dissociation constant that is independent of glass composition. These structural characteristics can be attributed to the high metallicity of Te and the strong energetic similarity between the Te鈥揟e, Te鈥揂s, and As鈥揂s bonds, and they are consistent with the monotonic and often nearly linear variation of physical properties observed in telluride glasses as a function of the Te content.