Structure, Microstructure, Composition and Properties of Lanthanum Lithium Titanates and some Substituted Analogues

The very high value of ionic conductivity at room temperature reported for La0.51Li0.34TiO2.94 some years ago did originate a great deal of interest in the study of materials of general formula La2/3–xLi3xTiO3 (LaLiTiO) and related systems. These oxides have shown to be potential solid electrolytes for lithium secondary batteries, but other aspects, apart from the conducting properties, such as their dielectric behaviour and crystal structure, have been the main focus of important studies in the area of inorganic solid‐state chemistry. LaLiTiO‐related compounds have the perovskite‐type structure (ABO3) with A‐cation ordering. However, essential details of their crystal structure, as for instance the location of the lithium atoms, are still under discussion and are the subject of current work. We show in this short review of mainly our own work that the complex microstructure of these materials, which has been studied in detail by transmission electron microscopy, is the cause of the difficulties on the precise determination of their crystal structure. We have developed a new approach for crystal structure refinement, which takes into account the microstructural effects, obtaining significantly better results than conventional methods of refinement. The microstructure of these oxides also affects their conducting and dielectric properties. Therefore, different parameters such as composition and microstructure must be considered to understand and, eventually, optimise, as we have done, the conducting properties of LaLiTiO‐related systems.