Quenching of lanthanide emission by intervalence charge transfer in crystals containing closed shell transition metal ions

The quenching of the luminescence originating from the excited states P-3(0) and D-1(2), of Pr3+ and D-5(3) and D-5(4) of Tb3+ has been studied in oxide crystals containing closed shell transition metal ions, such as titanates, vanadates, niobates, and tantalates. It has been shown that the emission from these excited states can be quenched by an intervalence charge transfer mechanism. The temperature dependence of the emission intensities has allowed estimating indicative activation energies for the crossover to the intervalence charge transfer state. In the case of Tb3+, the quenching gives rise to relatively short decay times for the D-5(4) state