The influences of deuterium irradiation defects on mechanical properties for ceramic breeder material Li2TiO3

•The reduction of Vickerness hardness is caused by F-center defects in Li2TiO3 crystalline grains after deuterium irradiation.•F-center defects in crystalline grains will be aggregated to form defect clusters with the increase of heating temperature, which lead to a hardening tendency within a certain temperature range.•The aggregated defect clusters in the crystalline grains begin to recover when the annealing temperature increases to a point temperature, which results in the decrease of Vickers hardness.