Aeschynite glass–ceramic composites as flexible wasteforms for minor actinide wastes

Glass–ceramic composites with MTiNbO₆ (M = Ce, Nd) ceramic phase and Na₂Al_2−xB_xSi₆O₁₆ (x = 0.5, 1, 1.5) glass phase have been produced from oxide precursors after reaction at 1200 °C for 4 h, and the impact of a range of variables was examined with respect to the formation of the aeschynite phases. Batched ceramic phase stoichiometries containing higher fractions of TiO₂ resulted in lower fractions of Nd- and Ce-containing non-aeschynite phases. The glass:ceramic ratio had a large impact on the final crystalline phase assemblage, with higher fractions of glass leading to larger amounts of non-aeschynite phases. Even materials comprising 90 wt% ceramic had fully reacted after only 4 h at 1200 °C, compared to the significantly longer timescales necessary for a full ceramic. The impact of the glass composition was also investigated, with high Al-content glasses preventing formation of non-aeschynite phases while still permitting formation of near-single-phase aeschynite.