Changes in mechanical property and microstructure of lithium metatitanate tritium breeder caused by thermal annealing

Highlights: • Changes in mechanical property and microstructure of sintered pebbles of Li₂TiO₃ and Li_2+xTiO₃, x > 0, were investigated. • The Li₂TiO₃ pebble was stable during the thermal annealing at 900 °C. • The grain growth of Li_2+xTiO₃, x > 0, was severe. • The excessive Li in Li_2+xTiO₃, x > 0, was disappeared in a 1000 h annealing. • The compressive strength of Li_2+xTiO₃, x > 0, was significantly changed during the thermal annealing. - Abstract: Changes in mechanical property and microstructure of sintered pebbles of lithium metatitanate (Li₂TiO₃) and Li excessive lithium metatitanate (Li_2+xTiO₃, x > 0) as tritium breeder pebbles for thermal fusion reactors, which were caused by thermal annealing, were investigated. The compressive strength was measured by using a universal tester. The Li₂TiO₃ pebble was stable during the thermal annealing at 900 °C, and its compressive strength was not decreased. In contrast, the microstructure and Li/Ti ratio of the Li_2+xTiO₃ pebble were markedly changed during the thermal annealing; the grain growth was severe and the excessive Li was disappeared in a 1000 h annealing. As a result, its compressive strength was significantly changed; it was drastically decreased by a 100 h annealing but it was once increased again in the additional annealing by a change in fracture mode.