ZHOU Qilai, ZHANG Yuguo, XU Yifu
(School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, Hubei, China)

Abstract: Ternary lithium ceramics can be used as the solid candidate tritium breeding materials in fusion reactors. Lithium orthosilicate (Li₄SiO₄) has fine tritium release performance owing to its relatively higher lithium density. However, the sintering of Li₄SiO₄ is challenging. The mechanical properties need to be improved. In this study, neutron multiplier elements Pb and Zr were added to increase the ceramic density and improve the mechanical properties via the control of the sinterability and the microstructure. The lead (Pb) with the content of 2 wt.%, 5 wt.% and 8 wt.% Pb was added into the precursor solution in the form of lead nitrate [Pb(NO₃)₂]. The ceramic powders were obtained by the microwave-induced solution combustion synthesis. The X-ray diffraction analysis shows that the effective phase was PbO. The ceramic density was increased by the addition of 2 wt. % Pb into ceramic. The relative density reached 90 % by sintering at 1273 K under an oxygen atmosphere. The bending strength of the ceramics was tested. The results showed that the mechanical properties can be improved by Pb addition. Therefore, it is known that although PbO can improve the densification process of ceramics, the enhancement of mechanical properties is difficult. Zr mainly existed as Li₂ZrO₃ after the introduction of 10 wt.% Zr in Li₄SiO₄. The ceramic grains were refined obviously. The density of the ceramic reached 86.19 %. The bending was related positively to the density. Further, the Li₄SiO₄-10 wt.% ZrO₂ pebbles were fabricated. The crush load reached 40.76 N.
Key words: tritium breeder; lithium orthosilicate; neutron multiplier; bending strength; crush load