Luminescence and red long afterglow investigation of Eu3+-Sm3+ CO-doped CaWO4 phosphor

► The afterglow of Eu3+ and its enhancement by Sm3+ co-doping in CaWO4 is studied. ► An optimal Sm3+ doping concentration for the Eu3+ afterglow properties was found. ► The mechanism of energy transfer between Sm3+ and Eu3+ is presented, and the proposed cause of long afterglow was discussed.