Influence of temperature on the 4f5d emission of Pr3+ in SrB4O7

The temperature-dependent emission spectra of Pr3+-doped SrB4O7 were investigated from 20 to 300 K under vacuum ultraviolet excitation. When the temperature was over 80 K, the interconfigurational 4f15d1→4f2 and intraconfigurational 4f2→4f2 emissions could be observed simultaneously. The theoretical model describing thermal equilibrium of the energy levels was applied successfully to the system concerning the lowest-energy 4f5d state and 1S0 state of SrB4O7:Pr3+. In addition, the decay curves of Pr3+ emissions from 300 to 600 K were also measured. The decay times of 4f5d emission and 1S0 emission were same for a certain temperature and became faster with increased temperatures, which further identified the validity of the model applied to the system. This paper clarified the nature of unusual temperature dependence of the emission spectra of Pr3+ in SrB4O7.