Nonstoichiometrically activated sintering for Li4SiO4 ceramic pebbles with a cauliflower-like nanostructure and enhanced properties

The advancement of Li 4 SiO 4 ceramics with enhanced performance represents a crucial research area within the domain of solid-state tritium breeding materials. However, the mechanical and physical properties of Li 4 SiO 4 are severely constrained by the challenge of balancing between densification and grain refinement. In this study, a ceramic with a high density and a distinctive cauliflower-like nanostructure is proposed. Specifically, Li 4 SiO 4 nanopowders with varying oxygen vacancy contents were obtained via the mechanical alloying process. The issues of low diffusivity and abnormal grain growth during the sintering of Li 4 SiO 4 ceramics were effectively addressed through the nonstoichiometrically activated sintering method. The resulting Li 4 SiO 4 ceramics exhibited a high relative density (90.21 % T.D.), exceptional mechanical strength (104 N), high thermal conductivity (2.98 W/m·K at room temperature and 1.91 W/m·K at 500 °C), and good ionic conductivity (4.20 × 10 −4  S/m). The findings indicated that the oxygen vacancies in Li 4 SiO 4 powders increased with the prolongation of the mechanical alloying period. This increase contributed to enhanced relative density, crushing load, and thermal conductivity of Li 4 SiO 4 ceramics, with only a slight decline in ionic conductivity. Concurrently, the oxygen vacancies in the ceramics were almost entirely annihilated by sintering under an air atmosphere. In conclusion, the utilization of nonstoichiometrically activated sintering offers significant advantages in the fabrication of tritium breeding ceramics with superior comprehensive characteristics.