A comprehensive study on Li₄Si_1-xTi_xO₄ ceramics for advanced tritium breeders

Hetero-element doped lithium orthosilicates have been considered as advanced tritium breeders due to the superior performances. In this work, Li₄Si_1-xTi_xO₄ ceramics were prepared by proprietary hydrothermal process and multistage reactive sintering. The reaction mechanism of Li₄Si_1-xTi_xO₄ was put forward. XRD and SEM analyses indicate that insertion of Ti leads to lattice expansion, which promotes the grain growth and changes the fracture mode. The compressive tests show that the crush load increases almost four times by increasing x from 0 to 0.2. However, the thermal conductivity and ionic conductivity are the best when x = 0.05 and x = 0.1, respectively. Thermal cycling stability of Li₄Si_1-xTi_xO₄ pebbles was further appraised through investigating the changes of microstructure and crush load. After undergoing thermal cycling, the Li₄Si_1-xTi_xO₄ still show higher crush load compared with Li₄SiO₄, despite Ti segregation in some samples. The x = 0.05 sample exhibits excellent thermal cycling stability. In summary, proper amount of Ti doping can improve the crush load, thermal and ionic conductivity, and thermal cycling stability of Li₄SiO₄.