The unusual variations of photoluminescence and afterglow properties in monoclinic ZrO2 by annealing

► ZrO2 shows unusual luminescence behaviors after annealing at high temperatures. ► The increase of emission at 492 nm at 1200-1450 °C is related to the reduction of Ti4+. ► The increase of afterglow at 1550 °C is due to the increase of shallow oxygen vacancies. ► We present a feasible interpretation for our observations.