Structural disorder in lithium lanthanum titanate: the basis of superionic conduction
Structural disorder in lithium lanthanum titanate: the basis of superionic conduction
复制标题
DOI：
10.1088/0953-8984/22/40/404203
复制
发表时间：
2010-10
期刊：
影响因子：
--
通讯作者：
Koji Ohara;Y. Kawakita;László Pusztai;L. Temleitner;Shinji Kohara;Naoki Inoue;S. Takeda
中科院分区：
文献类型：
--
作者：
Koji Ohara;Y. Kawakita;László Pusztai;L. Temleitner;Shinji Kohara;Naoki Inoue;S. Takeda
对多晶La_(2/3)−_xLi_3xTiO_3(0.075<；x<；0.165)进行了高能X射线和中子衍射测量。用反蒙特卡罗(RMC)模拟技术对总散射结构因子进行了分析，得到了粒子的三维构型。然后利用这些构型揭示了La和Li离子的分布，并了解了这些分布与离子导电性之间的关系。在x=0.075成分中发现沿c轴交替排列的富La层和贫La层。有趣的是，这种排列在锂浓度较高的样品中逐渐消失。此外，RMC模型显示了Li离子的无序分布，主要分布在富La层上，Li离子很可能占据了TiO6八面体的O-3三角平面与La离子或其空位之间的间隙位置(T位)。在RMC模型的基础上还发现，在低Li组分时，Li离子在富La层和贫La层上的键价和(BVS)表现不同，而在高Li组分时，BVS表现相似。这与富La层和贫La层交替排列的行为相一致。(1/2，0，0)(底层)瓶颈附近的Li离子可以通过T位跃迁到相邻的(0，1/2，0)瓶颈，不仅是贫La层中的Li离子，而且是富La层中的Li离子对瓶颈-瓶颈Li传导有贡献。
High-energy x-ray and neutron diffraction measurements on polycrystalline La2/3 − xLi3xTiO3 (0.075 < x < 0.165) were performed. The total scattering structure factors were analysed by the reverse Monte Carlo (RMC) modelling technique, resulting in three-dimensional particle configurations. These configurations were then used for revealing the distributions of La and Li ions and to understand the relationship between these distributions and ionic conduction. An alternating arrangement of La-rich and La-poor layers along the c-axis was found in the x = 0.075 composition. Intriguingly, this arrangement has gradually disappeared in samples with higher Li concentration. Furthermore, RMC models exhibit disordered distributions of Li ions, situated mainly on the La-rich layer, and there is a significant probability of Li ions occupying the interstitial sites (T site) between the O-3 triangle plane of the TiO6 octahedron and an La ion or its vacancy site. It was also found on the basis of the RMC models that the bond valence sum (BVS) for Li ions behaves differently on La-rich and La-poor layers at low Li concentration compositions, but they are similar at high Li concentration compositions. This is consistent with the behaviour of the alternating arrangement of La-rich and La-poor layers. It is also suggested that the Li ions around the bottleneck at (1/2, 0, 0) (bottom layer) can jump to an adjacent bottleneck at (0, 1/2, 0) through the T site and not only Li ions in the La-poor layers but also Li ions in the La-rich layers contribute to the bottleneck–bottleneck Li conduction.