Densification behavior and properties of Li4SiO4 ceramic breeder with the addition of SiC as a sintering aid

Abstract

Lithium orthosilicate (Li4SiO4) is regarded as a vital tritium breeder candidate due to its favorable properties, such as high lithium contents, superior tritium release behavior, and irradiation stability. However, the poor crushing load and low thermal conductivity of the Li4SiO4 ceramic pebbles fabricated via existing methods will lead to the blocking of the tritium release channels, giving rise to thermal stress concentration. To overcome the above shortcomings, the SiC was employed as sintering aid to improve Li4SiO4 ceramic pebbles via simple wet method in this paper. The effects of SiC content on the shrinkage, internal structure evolution, and crushing load of the Li4SiO4 ceramic pebbles are comprehensively investigated, and the densification process is analyzed in detail. It was found that the addition of SiC improves the crushing load (54 N) significantly owing to decreasing the densification activation energy. Moreover, the Li4SiO4 ceramic pebbles with excess Li2CO3 further displays excellent properties at 800 °C, such as the relative density of 90.3%, the crushing load of 65.3 N, and the thermal conductivity of 1.97 W/(m·K) respectively, which is much higher than that of traditional methods (at least 1000 °C). The Li4SiO4 ceramic pebbles with homogeneous micro-pore distribution, the porosity of 7.3% were further measured by using the X-ray computer tomography technique. Therefore, this proposed tactic has great prospects for the service performance of tritium breeding materials in the blanket.