Domain boundary structures in lanthanum lithium titanates
Domain boundary structures in lanthanum lithium titanates
复制标题
DOI：
10.1039/c3ta13726k
复制
发表时间：
2014-01-01
影响因子：
11.9
通讯作者：
Ikuhara, Yuichi
中科院分区：
文献类型：
--
作者：
Gao, Xiang;Fisher, Craig A. J.;Ikuhara, Yuichi
钙钛矿型钛酸镧锂（LLTO）由于其高的本征离子电导率而引起了人们的广泛关注。该材料表现出复杂的微观结构，具有随锂含量变化的各种尺寸和取向的域。基于使用最先进的扫描透射电子显微镜（STEM）对Li-贫和Li-富LLTO化合物进行的系统检查，我们揭示了畴界（DBs）的结构和组成，并考虑它们对Li-离子迁移率和离子电导率的影响，在此过程中假定微观结构变化的起源。这种材料中的DBs基本上由两种类型组成：经常发生的90度旋转DBs和不太常见的反相型边界。据发现，90度DBs是连贯的接口，由共享La网站的互联步骤，与占有率的La网站高于在域内部。在这两种化合物的微观结构的变化的起源是与不同程度的晶格失配应变在DB中的锂穷人和锂丰富的材料。晶格应变和相关的O空位，以及高的La占位，在DB预计会导致较低的域间锂离子迁移率，这将对整体离子电导率产生有害影响。
Perovskite-type lanthanum lithium titanate (LLTO) is attracting extensive interest because of its high intrinsic ionic conductivity. The material exhibits a complex microstructure with domains of various sizes and orientations that vary with the lithium content. Based on a systematic examination of both Li-poor and Li-rich LLTO compounds using state-of-the-art scanning transmission electron microscopy (STEM), we reveal the structures and composition of the domain boundaries (DBs) and consider their effect on Li-ion mobility and ionic conductivity, in the process positing the origin of the microstructural variations. DBs in this material are shown to consist essentially of two types: frequently occurring 90 degrees rotation DBs and a much less common antiphase-type boundary. It is found that the 90 degrees DBs are coherent interfaces consisting of interconnected steps that share La sites, with occupancies of La sites higher than in the domain interiors. The origin of microstructural variations in the two compounds is associated with different degrees of lattice mismatch strain at DBs in Li-poor and Li-rich materials. The lattice strain and associated O vacancies, as well as the high La occupancies, at DBs are expected to result in lower interdomain Li-ion mobility, which will have a deleterious effect on the overall ion conductivity.