Synthesis and Characterization of Li₄SiO₄ Ceramics from Rice Husk Ash by a Solution-Combustion Method

Phase-pure lithium orthosilicate (Li₄SiO₄) was prepared by a solution-combustion technique using rice husk ash as a silica source. We found that by controlling the citrate-to-metal (C/M) ratio of the solution and the calcination temperature of the as-burnt powder, phase purity can be achieved. The particle size of the Li₄SiO₄ powder (prepared at a C/M ratio of 1.4) was found to be 100 to 200 nm with a low surface area (1.83 m²/g). It was found that Li₄SiO₄ powder can be sintered at a temperature as low as 900°C with a density of ∼83% of the theoretical density. Phase stability in the sintered sample was studied. Attempts were made to minimize lithium loss from the sintered specimens. The solution-combustion–derived Li₄SiO₄ fractured pellets showed narrow pore size distributions with pore diameters in the range 0.2 to 10 μm. Thermal diffusivity was measured using a laser flash method. Thermal conductivity values depend on the density of the sample. An impedance spectroscopy method has been used to characterize the electrical properties of the sintered sample as tritium diffusion is related to Li⁺ ion conductivity in Li₄SiO₄.