Development of fine-grained Li2(Ti,Zr)O3-Li4SiO4 biphasic ceramic pebbles via a solid solution-composite dual strategy

Advanced tritium breeder materials with high lithium density, robust mechanical strength, and fine grain size are prerequisites for the safe and efficient operation of fusion blankets. While Li 2 TiO 3 -Li 4 SiO 4 biphasic ceramics have been developed to balance the trade-offs between single-phase breeders, achieving rigorous control over microstructure stability at elevated temperatures remains a challenge. In this work, a dual-optimization strategy combining solid solution strengthening and biphasic compositing was proposed. Novel Li 2 (Ti,Zr)O 3 -Li 4 SiO 4 ceramic pebbles with various phase ratios (Ti/Si atomic ratio = 1:0.5, 1:1, and 1:2) were successfully prepared for the first time. The introduction of Zr into the Li2TiO3 lattice serves as a grain growth inhibitor, while the Li 4 SiO 4 phase enhances sinterability. The results indicate that pure-phase and well-crystallized powders can be obtained at 700 °C. Interestingly, the addition of Li 4 SiO 4 was found to hinder the phase transition of Li 2 (Ti,Zr)O 3 effectively. Benefiting from the synergistic effect, the pebbles sintered at 1000 °C exhibit a refined grain size of <2 μm, significantly smaller than that of traditional Li 4 SiO 4 -based ceramics. Meanwhile, a satisfactory relative density of ∼82 %T.D. and a high crushing load of >70 N were achieved due to the improved sinterability. This study demonstrates that the Li 2 (Ti,Zr)O 3 -Li 4 SiO 4 ceramic, which integrates the advantages of structural stability from solid solutions and mechanical robustness from biphasic composites, holds great promise as a high-performance tritium breeder.