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 4d¹5d¹ 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. (paper)