NMR Research Centre, Indian Institute of Science, Bangalore, 560012, India; Physics Department, Indian Institute of Science, Bangalore, 560012, India.
Department of Physics, Goa University, Taleigao Plateau, Goa, 403206, India.
Solid State Nucl Magn Reson. 2017 Jul-Aug;84:204-209. doi: 10.1016/j.ssnmr.2017.05.001. Epub 2017 May 12.
This paper reports results of Na and Si solid-state NMR investigations carried out on sodium strontium silicate ion conductor, SrNaSiO and presents the first experimental evidence to show that different synthesis conditions induce multiple devitrified phases. Along with 1-dimensional NMR, Na MQMAS spectra have been used to identify the phases corresponding to polymorphs of NaSiO, in addition to the crystalline SrSiO and the glass/amorphous NaSiO phases. The surprising observation of about an order of magnitude higher ionic conductivity achieved in devitrified samples is attributed to the growth of the crystalline δ-NaSiO phase within the amorphous NaSiO phase domains, identified using NMR. Together with XRD and conductivity measurement data, the study leads to the identification of the chemical phase composition and an understanding of the composition-property-structure correlation in this material. Present findings, while do not show any evidence of Na doping in the SrSiO phase confirming earlier reports, explain the large discrepancy in the conductivity reported in the literature.
本文报道了钠离子和硅固态 NMR 研究结果，该研究针对的是钠离子锶硅酸盐导体 SrNaSiO，并首次提供了实验证据，表明不同的合成条件会导致多种非晶态相的形成。除了晶态 SrSiO 和玻璃/非晶态 NaSiO 相之外，一维 NMR 和 Na MQMAS 谱还被用于鉴定与 NaSiO 多晶型物相对应的相。在非晶态样品中观察到离子电导率提高了一个数量级，这一令人惊讶的现象归因于 NMR 鉴定出的在非晶态 NaSiO 相域内生长的晶态 δ-NaSiO 相。结合 XRD 和电导率测量数据，该研究确定了化学相组成，并理解了该材料中的组成-性能-结构关系。目前的发现虽然没有任何证据表明 SrSiO 相中存在 Na 掺杂，这与早期的报告一致，但也解释了文献中报道的电导率存在较大差异的原因。
