Determination of the influence of component ratio variation in solid-phase synthesis of lithium-containing ceramics based on lithium aluminate

As is known, synthesis of high-strength, stable lithium-containing ceramics capable of withstanding high mechanical loads during operation is one of the key problems in the field of materials science, the solution of which will determine the potential for using new lithium-containing ceramics for blankets. In the work, using the method of mechanical mixing and subsequent thermal annealing, samples of lithium-containing ceramics based on lithium aluminate were obtained, and the variation of the ratio of the components during mixing made it possible to obtain ceramic samples with different phase ratios, a change in which, according to the data obtained, leads to a change in the strength and mechanical properties of the ceramics. According to X-ray diffraction analysis and Raman spectroscopy data, it was found that variation in the ratio of components in the composition of lithium aluminate due to an increase in the proportion of aluminum oxide leads to the formation of glass phases, as well as transformations of the tetragonal phase LiAlO2 into the cubic LiAl5O8 with subsequent dominance of this phase in the composition at concentrations of 0.9 M Al2O3. Moreover, the analysis of optical spectra showed that the change in the phase ratio is accompanied by the formation of oxygen vacancies, the minimum density of which is observed for samples of single-phase ceramics with the tetragonal phase LiAlO2. The evaluation results of the mechanical properties of ceramics showed that the formation of two-phase ceramics containing the tetragonal phase LiAlO2 and the orthorhombic phase Li5AlO4 leads to higher hardness and crack resistance compared to single-phase LiAlO2 ceramics. At the same time, the formation of two-phase ceramics, including the cubic phase LiAl5O8, leads to less pronounced changes in resistance to external influences due to the presence of glass-phase inclusions in the structure.