Cerâmica de titanato de lantânio e lítio: sistematização de obtenção e crescimento de grão orientado induzido via cristais de aluminato de lantânio

Abstract

The research based on ionic conductive ceramics is part of the scientific innovation efforts applied to the industry of solid state batteries and sensors, which are fundamental for the development of new, more efficient and sustainable technologies. One of the most relevant examples found in the current scientific literature is the lithium lanthanum titanate (LLTO) ceramics, whose ambient temperature conductivity is one of the largest available among solid state lithium conductive materials. However, ceramic processing difficulties and controversies about the compositional nature of this ceramic material still unclear to the scientific community. Even so, the success in the use of this ceramic material, as electrolyte or pH sensor, leaves no doubt about its promising character in scientific and technological innovation on diverse fields of applications. The aim of this thesis is to present a systematic study on the ceramic processing of LLTO (x ≈ 0.10, 0.11 and 0.12) ceramics, based on the motivation for technological application of this compound as electrolyte or solid state pH sensor. The introduction of single crystals in the ceramic processing were also investigated, culminating in development of a LLTO crystal/ceramic composite with crystal fibers from lanthanum aluminate (LAO). The results show the structural and microstructural evolution from the LLTO ceramics, sintered at temperatures above 1250 °C, strongly correlated to the overfiring phenomena with the electrical properties having an inversely proportional behavior as a function of the sintering temperature. The formation of textured LLTO regions around the LAO crystals is also showed. The nature of this region is chemically and structurally very similar to the ceramic matrix, however, its creation results in composites with ionic conductivities about 5 times higher than the LLTO.