Preparation, performances and reaction mechanism of the Li4+xAlxSi1−xO4 pebbles for advanced tritium breeders

The interstitial solid solution Li4+xSi1-xAlxO4 (x > 0) pebbles have been considered as potential candidates for the next generation of advanced tritium breeders. In this paper, Li4+xSi1-xAlxO4 (x = 0.1, 0.2, 0.3) pebbles were fabricated by a graphite bed method using two alternative raw materials (Li2CO3, SiO2 and Al2O3; Li4SiO4 and Li5AlO4). The reaction process of Li2CO3 and Al2O3 was investigated by thermogravimetry-differential thermal analysis (TG-DTA) and X-ray diffractometer (XRD), which can be divided into two steps. LiAlO2 would be formed inevitably in the first step (400-700 °C) during the calcination process of the Li2CO3, SiO2 and Al2O3 raw materials, and it can hardly be incorporated into Li4SiO4, resulting biphasic Li4SiO4-LiAlO2 pebbles. The interstitial solid solution Li4+xAlxSi1−xO4 pebbles can be fabricated by the graphite bed method using Li4SiO4 and Li5AlO4 as raw materials. The Al replacement increased the grain growth of Li4SiO4. The optimal x values seemed to be 0.1. Crush load and density of the Li4.1Al0.1Si0.9O4 pebbles reached 48.2 N and 86.4% TD, respectively.