Excitation energy dependence for electron traps in CaTiO3:Pr, Al single crystals

We investigated the red afterglow process of CaTiO3:Pr, Al through photoluminescence and thermoluminescence measurements by using fabricated single crystals. The crystals with several cubic millimeter in size were obtained through a flux method. We found that the afterglow properties varied with the excitation energy. At room temperature, the red afterglow was observed for the charge transfer from Pr3+ to Ti4+ excitation and the direct excitation of Pr3+, while not observed for the interband excitation of CaTiO3 due to the relaxation process going through 4d(1)5d(1) state of Pr3+. For the direct excitation of Pr3+ at 80 K, the excited electrons did not reached to trap states for afterglow due to a potential barrier, which can overcome with thermal assistance at room temperature. For the charge transfer excitation at 80 K, the excited electrons could reach the traps with excess energy.