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

The radiationless relaxation pathways leading to the quenching of P-3(0) emission and subsequent atypical single red luminescence from D-1(2) level in CaTiO3:Pr3+ are studied under UV excitation. Self-trapped excitons are shown to participate in the relaxation process and Pr3+ /Ti4+ reversible arrow Pr4+ /Ti3+ charge transfer state (CTS) is proposed as the final relaxation channel to the emitting D-1(2) level. This mechanism is supported by EPR investigations showing an increase of paramagnetic [Pr4+Ti3+O3](+) clusters upon optical excitation in the CTS. (C) 2004 Elsevier B.V. All rights reserved.