LGSO:Ce scintillation crystal optimization by thermal treatment

•Optimization of the post-growth annealing regimes is performed for the full range of Lu2−xGdxSiO5:Ce scintillation crystals grown from melt by the Czochralski method.•The heat treatment in air at 1100°C provides the improvement in the LGSO:Ce energy resolution up to 6.7% at 662keV.•Higher temperatures and the longer durations of heat treatment in air are inappropriate, because the optimized conditions must provide decrease in oxygen vacancies concentration avoiding Ce4+ formation.