Nizamutdinova Alina, Uesbeck Tobias, Grammes Thilo, Brauer Delia S, van Wüllen Leo
Institute of Physics, Augsburg University, Universitätsstrasse 1, 86159 Augsburg, Germany.
Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Fraunhoferstrasse 6, 07743 Jena, Germany.
J Phys Chem B. 2020 Apr 2;124(13):2691-2701. doi: 10.1021/acs.jpcb.9b11403. Epub 2020 Mar 25.
In this contribution we present a detailed study of the effect of the addition of small to intermediate amounts of PO (up to 7.5 mol %) on the network organization of metaluminous sodium aluminosilicate glasses employing a range of advanced solid state NMR methodologies. The combined results from MAS, MQMAS (multiple quantum MAS), or MAT (magic angle turning) NMR spectroscopy and a variety of dipolar based NMR experiments-Al{P}-, Al{Si}-, Si{P}-, and P{Si}-REDOR (rotational echo double resonance) NMR spectroscopy as well as P{Al}- and Si{Al}-REAPDOR (rotational echo adiabatic passage double resonance) NMR-allow for a detailed analysis of the network organization adopted by these glasses. Phosphate is found as Q, Q, and Q (with the superscript denoting the number of bridging oxygens), the Q units can be safely identified with the help of P MAT NMR experiments. Al exclusively adopts a 4-fold coordination. The withdrawal of a fraction of the sodium cations from AlO units that is needed for charge compensation of the Q units necessitates an alternative charge compensation scheme for these AlO units via formation of Q units or oxygen triclusters. The dipolar NMR experiments suggest a strong preference of P for Al with an average value of ca. 2.4 P-O-Al connections per phosphate tetrahedron. P is thus mainly integrated into the network via P-O-Al bonding, the formation of Si-O-P bonding plays only a minor role.
在本论文中，我们运用一系列先进的固态核磁共振方法，详细研究了添加少量至中等量的PO（高达7.5摩尔%）对金属钠铝硅酸盐玻璃网络结构的影响。通过MAS、MQMAS（多量子MAS）或MAT（魔角旋转）核磁共振光谱以及各种基于偶极的核磁共振实验——Al{P}-、Al{Si}-、Si{P}-和P{Si}-REDOR（旋转回波双共振）核磁共振光谱以及P{Al}-和Si{Al}-REAPDOR（旋转回波绝热通道双共振）核磁共振得到的综合结果，使得我们能够对这些玻璃所采用的网络结构进行详细分析。发现磷酸盐以Q⁰、Q¹和Q²（上标表示桥氧原子的数量）形式存在，借助P MAT核磁共振实验可以安全地识别出Q单元。Al仅采用4配位。从AlO单元中抽出一部分用于Q单元电荷补偿所需的钠离子，这就需要通过形成Q单元或氧三聚体为这些AlO单元提供一种替代的电荷补偿方案。偶极核磁共振实验表明，P强烈倾向于与Al结合，每个磷酸四面体平均约有2.4个P-O-Al连接。因此，P主要通过P-O-Al键合融入网络，Si-O-P键合的形成只起次要作用。
