UV-to-red relaxation pathways in CaTiO3:Pr3+

The radiationless relaxation pathways leading to the quenching of 3P0 emission and subsequent atypical single red luminescence from 1D2 level in CaTiO3:Pr3+ are studied under UV excitation. Self-trapped excitons are shown to participate in the relaxation process and Pr3+/Ti4+⇋Pr4+/Ti3+ charge transfer state (CTS) is proposed as the final relaxation channel to the emitting 1D2 level. This mechanism is supported by EPR investigations showing an increase of paramagnetic [Pr4+Ti3+O3]+ clusters upon optical excitation in the CTS.