Synthesis and crystallographic studies of garnet-related lithium-ion conductors Li6CaLa2Ta2O12 and Li6BaLa2Ta2O12
Synthesis and crystallographic studies of garnet-related lithium-ion conductors Li6CaLa2Ta2O12 and Li6BaLa2Ta2O12
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DOI：
10.1016/j.ssi.2008.10.022
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发表时间：
2009-05-14
影响因子：
3.2
通讯作者：
Akimoto, Junji
中科院分区：
文献类型：
--
作者：
Awaka, Junji;Kijima, Norihito;Akimoto, Junji
采用固相反应法制备了高纯度的Li6CaLa2Ta2O12和Li6BaLa2Ta2O12样品。这些样品的分析化学成分与Li6CaLa2Ta2O12和Li6BaLa2Ta2O12的名义成分一致。Rietveld精修证实了这些化合物具有石榴石结构，Li6CaLa2Ta2O12的点阵常数a=12.725(2)埃，Li6BaLa2Ta2O12的点阵常数a=13.001(4)埃。X射线粉末衍射图的所有衍射峰都是在立方对称性的基础上很好地指标化的，空间群为1a-3d。为了寻找U位，用最大熵方法精确计算了U位的电子密度分布。Li+离子在这些化合物中部分占据两种晶位：(I)四面体24d位和(Ii)扭曲八面体96h位，后者是理想石榴石结构的空位。Li6CaLa2Ta2O12和Li6BaLa2Ta2O12在27℃(E-a=0.50 eV)和25℃(E-a=0.44 eV)的电导率分别为sigma=2.2×10(-6)S cm(-1)和1.3×10(-5)S cm(-1)。(C)2008爱思唯尔B.V.保留所有权利。
High-purity specimens of Li6CaLa2Ta2O12 and Li6BaLa2Ta2O12 have been successfully synthesized by solid-state reactions. The analytical chemical compositions of these samples were in good agreement with the nominal compositions of Li6CaLa2Ta2O12 and Li6BaLa2Ta2O12. The Rietveld refinements verified that these compounds have the garnet-type framework structure with the lattice constants of a = 12.725(2) angstrom for Li6CaLa2Ta2O12 and a = 13.001(4) angstrom for Li6BaLa2Ta2O12. All of the diffraction peaks of X-ray powder diffraction patterns were well indexed on the basis of cubic symmetry with space group la-3d. To make a search for U sites, the electron density distributions were precisely examined by using the maximum entropy method. Li+ ions occupy partially two types of crystallographic site in these compounds: (i) tetrahedral 24d sites, and (ii) distorted octahedral 96h sites, the latter of which are the vacant sites of the ideal garnet-type structure. The present Li6CaLa2Ta2O12 and Li6BaLa2Ta2O12 samples exhibit the conductivity sigma = 2.2 x 10(-6) S cm(-1) at 27 degrees C (E-a = 0.50 eV) and sigma = 1.3 x 10(-5) S cm(-1) at 25 degrees C (E-a = 0.44 eV), respectively. (C) 2008 Elsevier B.V. All rights reserved.