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Low-temperature synthesis of Li4SiO4 pebbles as tritium breeding material by SiO2 coating approach

ABSTRACT Li4SiO4 pebbles are widely selected as attractive ceramic tritium breeding materials for the test blanket modules (TBM) of international thermonuclear experimental reactor (ITER). In this work, SiO2 coating approach was first employed to synthesize precursor powders for fabricating the Li4SiO4 pebbles. Lithium source and silicon source were mixed by hydrolyzing tetraethyl orthosilicate (TEOS) in the Li2CO3 solution. Compared with the traditional solid state method, the precursor powders synthesized by SiO2 coating approach displayed distinct coating structure, which was able to effectively lower the phase formation temperature and the sintering temperature of Li4SiO4 pebbles, and then decrease the grain size of Li4SiO4 pebbles. Thermogravimetry and different scanning calorimetry (TG-DSC) and X-ray diffraction (XRD) analyses indicate that the phase formation temperature of Li4SiO4 synthesized by SiO2 coating approach is far below that of the conventional solid state reaction. Then, wet method was employed to prepare green spheres with the as-prepared precursor powders. Finally, Li4SiO4 pebbles with small grain size (average value 1.12 µm), high phase purity, good sphericity, and uniform microstructure could be obtained by sintering the green spheres at a low temperature of 625°C, which are expected to show favorable tritium release behavior and be used as tritium breeding materials for blankets.