Textured lithium lanthanum titanate polycrystals prepared by a reactive-templated grain growth method

Abstract

Textured polycrystals of lithium lanthanum titanate (La(2/3)−xLi3xTiO3, 3x=0.16 and 0.33) were topochemically designed and fabricated by the heat treatment of stacked tape-cast sheets including aligned elongated La2Ti2O7 platelets as reactive templates. The crystallographic orientation relationship between the reactive template and the resultant sintered bodies was examined by X-ray diffraction analysis. A small amount of the plate-like template effectively controlled the crystallographic orientation of the sintered bodies and the Lotgering factor for the pseudocubic {110} with a 3x=0.16 composition reached as high as 0.65 for the polished surface parallel to the original sheet. A secondary preferred orientation of the pseudocubic {100} was also detected in the polycrystals with 3x=0.16 for sections perpendicular to the sheet forming direction as a result of the elongated shape of the template. The formation of biaxially oriented polycrystals can be explained by the inheritance of octahedral TiO6 blocks from the layered to regular perovskites.