The Structure of Borophosphosilicate Pure Network Former Glasses Studied by Multinuclear NMR Spectroscopy

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• 作者：Tobias Uesbeck ; Hellmut Eckert ; Randall Youngman ; Bruce Aitken
• 刊名：Journal of Physical Chemistry C
• 出版年：2017
• 出版时间：January 26, 2017
• 年：2017
• 卷：121
• 期：3
• 页码：1838-1850
• 全文大小：716K
• ISSN：1932-7455

文摘

New mixed network glasses along the composition line xB₂O₃–(30 – x)P₂O₅–70SiO₂ have been prepared and characterized in terms of their chemical composition, viscosity, and characteristic temperatures. The physical properties have been correlated with structural information, obtained from Raman spectroscopy and advanced ¹¹B, ²⁹Si, and ³¹P single and double resonance solid state NMR studies. Both the macroscopic and structural properties show nonlinear changes as a function of composition, with maximal values of the viscometric glass transition temperature near 12–13 mol % B₂O₃. The structure of phosphorus-rich glasses is dominated by tetrahedral B⁽⁴⁾ units linked to three to four phosphorus species and multiple phosphorus environments, including P⁽³⁾ (branching phosphate) groups linked to silicon, and P⁽⁴⁾ units forming B–O–P linkages as in boron phosphate, BPO₄ (superscripts denote the number of bridging oxygen species). In the boron-rich region, the phosphorus species are exclusively present as P⁽⁴⁾ groups and the boron atoms present in excess of a B/P ratio of unity are present in the form of three-coordinated B⁽³⁾ units forming both B–O–B and B–O–Si linkages. While these results document a strong mutual affinity of the boron oxide and phosphorus oxide components, the species concentrations and numbers of B–O–P linkages fall consistently below those numbers expected from a clustering scenario maximizing the number of such connectivities, indicating the absence of macroscopic phase separation. Important differences relative to the previously studied system xAl₂O₃–(30 – x)P₂O₅–70SiO₂ are discussed.