Christian Doppler Laboratory for Lithium Batteries, and Institute for Chemistry and Technology of Materials, Graz University of Technology (NAWI Graz), Stremayrgasse 9, 8010 Graz, Austria.
Phys Chem Chem Phys. 2019 Jan 23;21(4):1872-1883. doi: 10.1039/c8cp07206j.
Diffusion of small ions in materials with confined space for translational dynamics can be quite different to isotropic (3D) diffusion, which is found in the majority of solids. Finding credible indications for 2D diffusion is not as easy as it looks at first glance, especially if only powder samples are available. Here we chose the ternary fluoride RbSn2F5 as a new model system to seek out low-dimensional anion diffusion in a nanocrystalline material. We prepared RbSn2F5via mechanochemically-assisted solid state synthesis and used both ac conductivity spectroscopy and spin-lock NMR relaxation measurements to find evidence that the fluorine ions preferably diffuse between the Rb-rich layers. In both cases the diffusion induced spin-lock NMR rates are only consistent with conductivity data if they are analyzed with the semi-empirical spectral density function for 2D jump diffusion as introduced by P. M. Richards [Solid State Commun., 1978, 25, 1019].
在具有受限平移动力学空间的材料中，小分子离子的扩散与各向同性（3D）扩散有很大的不同，后者存在于大多数固体中。要找到可信的二维扩散迹象并不像乍一看那么容易，特别是如果只有粉末样品可用的话。在这里，我们选择了三元氟化物 RbSn2F5 作为一个新的模型系统，在纳米晶材料中寻找低维阴离子扩散。我们通过机械化学辅助的固态合成制备了 RbSn2F5，并同时使用交流电导率光谱和自旋锁定 NMR 弛豫测量来寻找证据，证明氟离子优先在富铷层之间扩散。在这两种情况下，如果用 P. M. Richards 引入的二维跳跃扩散半经验谱密度函数来分析扩散诱导的自旋锁定 NMR 速率，那么它们与电导率数据是一致的。[固态通信，1978，25，1019]。
