Nippon Steel & Sumitomo Metal Corporation, 20-1 Shintomi, Futtsu, Chiba 293-8511, Japan.
Solid State Nucl Magn Reson. 2017 Jul-Aug;84:158-163. doi: 10.1016/j.ssnmr.2017.03.001. Epub 2017 Mar 3.
Structural roles of Ca in aluminosilicate glasses have been investigated by solid-state Ca, O, and Al NMR spectroscopy. In 15AlO-55SiO-15CaO-15RO (R=Mg, Ca, Sr, and Na) (mol%) glass systems wherein half of the alkaline plus alkaline-earth cations charge-compensate (AlO) tetrahedra and the other half modify the glass network, with decreasing cation field strength (CFS) in the order of Mg>Ca>Sr>Na, the isotropic chemical shift (δ) of Ca moves to a higher frequency and the quadrupolar coupling constant (P) of Ca decreases. The change in the δ of Ca is more sensitive to the role of Ca than that in the P of Ca. The two possible roles (network modifier and charge compensator) of Ca in the glass with R=Ca are not distinguished in the Ca 3QMAS and 5QMAS spectra. The O 3QMAS results demonstrate that the cation with higher CFS (e.g., Mg in the R=Mg glass and Ca in the R=Na glass) dominantly creates non-bridging oxygen, even though there is slight cation mixing. With increasing CFS in the glass, the P of both Ca and Al also increases, indicating that the cation with higher CFS tends to degrade the structural symmetry.
通过固态 Ca、O 和 Al NMR 光谱研究了铝硅酸盐玻璃中 Ca 的结构作用。在 15AlO-55SiO-15CaO-15RO（R=Mg、Ca、Sr 和 Na）（摩尔%）玻璃体系中，一半的碱金属和碱土金属阳离子电荷补偿（AlO）四面体，另一半改变玻璃网络，阳离子场强（CFS）依次降低，Mg>Ca>Sr>Na，Ca 的各向同性化学位移（δ）向更高的频率移动，Ca 的四极耦合常数（P）降低。Ca 的δ的变化比 Ca 的 P 的变化对 Ca 的作用更敏感。在 R=Ca 的玻璃中，Ca 的两种可能作用（网络改性剂和电荷补偿剂）在 Ca 3QMAS 和 5QMAS 光谱中无法区分。O 3QMAS 结果表明，具有较高 CFS 的阳离子（例如，R=Mg 玻璃中的 Mg 和 R=Na 玻璃中的 Ca）主要形成非桥氧，尽管存在轻微的阳离子混合。随着玻璃中 CFS 的增加，Ca 和 Al 的 P 也增加，这表明具有较高 CFS 的阳离子往往会降低结构对称性。
