物理化学学报

所属专题: 固体核磁共振

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固体核磁共振研究碱土金属磷硅酸盐玻璃的六配位硅结构

石峰1,2, 胡丽丽2, 任进军2, 杨秋红1   

  1. 1 上海大学材料科学与工程学院, 上海 200444;
    2 中国科学院上海光学精密机械研究所, 高功率激光材料重点实验室, 上海 201800
  • 收稿日期:2019-02-22 修回日期:2019-04-15 录用日期:2019-04-16 发布日期:2019-04-19
  • 通讯作者: 任进军 E-mail:renjinjunsiom@163.com
  • 基金资助:
    国家自然科学基金(61675218)和中国科学院百人计划资助项目

Structural Investigation of Alkaline-Earth Phosphosilicate Glasses Containing Six-Coordinated Silicon by Solid-State NMR

SHI Feng1,2, HU Lili2, REN Jinjun2, YANG Qiuhong1   

  1. 1 School of Materials Science and Engineering, Shanghai University, Shanghai 200444, P. R. China;
    2 Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, P. R. China
  • Received:2019-02-22 Revised:2019-04-15 Accepted:2019-04-16 Published:2019-04-19
  • Contact: REN Jinjun E-mail:renjinjunsiom@163.com
  • Supported by:
    The project was supported by the National Natural Science Foundation of China (61675218) and the 100 Talents Program of Chinese Academy of Sciences.

摘要: 磷酸盐玻璃在光学领域有广泛的应用,然而因为简单的磷酸盐玻璃的化学稳定性和热机械性能较差,已经难以满足日益发展的激光装置的高性能要求。在磷酸盐玻璃中加入少量的硅可以形成六配位的硅网络体并且极大的改善这些性能。因此研究这种磷硅酸盐玻璃的结构细节有重要的意义。但是由于玻璃结构缺乏长程有序,其结构研究比较复杂。现代固体核磁共振(NMR)技术能够从原子尺度对无序状态的物质局域结构进行解析,是一种强大的用来研究玻璃结构的技术手段。本文的目的是探究碱土金属对磷硅酸盐玻璃中六配位硅结构的影响。我们采用传统的熔融-冷却法制备了(2MO-3P2O5(1-x·(SiO2x(M=Ca,Sr,Ba)体系的磷硅酸盐玻璃。并且运用先进的固体核磁共振技术和拉曼光谱对此磷硅酸盐玻璃结构进行了表征。31P和29Si MAS NMR表明其网络结构由磷氧四面体P(2)和P(3)与四配位和六配位的硅氧多面体相互连接构成,随着二氧化硅含量的增加六配位硅的比例呈现减少的趋势。类似地,在拉曼光谱的结构中和六配位硅相连的磷基团的峰也随着硅含量的增加而减弱。基于双量子相干和P-P同核间J耦合作用的重聚INADEQUATE实验证明了不同的磷氧四面体之间的连接情况,P(2)和P(3)两种结构单元在玻璃中是相对分离的,他们大多数都是与自身相连接。和之前报道的有关Na2O-P2O5-SiO2体系的玻璃相比较,不同的是,在Na2O-P2O5-SiO2玻璃中一个P(3)结构单元最多有一个Si(6)-O-P(3)键,而对于本文的碱土金属磷硅酸盐玻璃一个P(3)结构单元最多有0.4-0.7个Si(6)-O-P(3)键。说明碱土金属比碱金属对六配位硅的稳定作用更弱一些。这种结构与组成之间的关系对设计玻璃组成和性质能提供重要的依据,尤其在大型的激光装置中对磷酸盐玻璃基质的化学和热稳定性有着很高的要求,详细的结构信息能为通过改变组成来提高善玻璃性能搭建桥梁。

关键词: 固体核磁共振, 玻璃结构, 六配位硅, 碱土金属, 磷硅酸盐玻璃

Abstract: Phosphate glass is widely used in optical applications; however, its generally low chemical stability and poor thermal mechanical properties hinder the application of phosphate glass to the rapidly evolving laser industry. The addition of a small amount of silicon can form a six-coordinate Si (Si(6)) network and improve the above-mentioned poor properties of phosphate glass. Therefore, it is important to characterize and understand the structural details of phosphosilicate glasses. It is difficult to investigate the glass structure because of its complicated and disordered characteristics. However, solid-state nuclear magnetic resonance (NMR) spectroscopy can provide detailed local structural information, regardless of the presence of its long-range order. To study the effect of alkaline earth metals on Si(6) species formation, we prepared phosphosilicate glasses (2MO-3P2O5)(1-x)·(SiO2)x (M=Ca, Sr, Ba) by conventional melt-quenching, and the glass structure was investigated by solid-state NMR and Raman spectroscopy. The 31P and 29Si NMR spectra indicated that the glass networks consisted of P(2) and P(3) tetrahedrons linked via four-and six-fold coordinated silicon units (Si(4) and Si(6)). The fraction of six-coordinated silicon Si(6) decreased with increasing SiO2 content. Similarly, the Raman spectra showed that the vibration band of the P=O stretching mode in P(3) linked with Si(6) neighbors reduced as the silica content increased. The connectivities between various phosphorus species were probed by 31P one-and two-dimensional refocused INADEQUATE experiments. This experimental technique is based on homonuclear J-coupling and yields correlation peaks between nuclei engaged in P-O-P linkages (P(2) and P(3) units). The signals from isolated 31P nuclei are suppressed because of the absence of J-coupling, which precludes the formation of double quantum coherences. The results indicated the segregation of P(2) and P(3) units in the prepared glass, which were also compared with those in the previously reported Na2O-P2O5-SiO2 glasses. They differed from alkali phosphosilicate glasses, where each P(3) unit exhibited a maximum average of one Si(6)-O-P(3) linkage, and in the alkaline earth phosphosilicate glasses, the average was approximately 0.4-0.7. When the content of Si(6) units reached its maximum, further increase in the SiO2 content did not increase the Si(6) content, and the surplus Si were present as Si(4). Alkaline earth metal ions exhibit weaker stabilizing effects for Si(6) species. Based on the results presented herein, we constructed sketches to illustrate the local structural organization of the glass. The relationships between the compositions and structures are important for glass composition and property design. It is important to improve the performance of phosphate glass by changing its composition, particularly for large laser device applications.

Key words: Solid state NMR, Glass structure, Six-coordination silica, Akaline-earth, Phosphosilicate glasses

MSC2000: 

  • O641