Fabrication of modified lithium orthosilicate pebbles by addition of titania

Lithium orthosilicate pebbles are one of the ceramic tritium breeder materials destined for the European solid breeder test blanket modules of ITER, the large-scale scientific experiment intended to prove the viability of fusion as an energy source, presently under construction in Cadarache, France. While the current reference material is fabricated by melt-spraying with 2.5 wt.% excess of silica, resulting in a two-phase material of lithium orthosilicate and metasilicate, a modified melt-based process was used to fabricate breeder pebbles with additions of titania in order to obtain pebbles with lithium metatitanate as a secondary phase. The fabricated two-phase pebbles exhibit a fine-grained microstructure and increased crush loads. The optimum titanate content has yet to be evaluated, nonetheless the pebbles may have the potential to combine the advantages of both lithium orthosilicate and metatitanate breeder ceramics.

► Lithium orthosilicate pebbles with additions of titania were fabricated by a modified melt-based process. ► The fabricated pebbles exhibit a very fine-grained microstructure with lithium metatitanate as a secondary phase. ► Due to the addition of titanate, the crush load of the pebbles was significantly increased. ► The closed porosity was found to be slightly increased with increasing titanate content.