Influence of the 4f5d-1S0 energy gap on the decay times of Pr3+-doped fluoride scintillating glasses

A comparative analysis of praseodymium (Pr³⁺)-doped fluoride glasses, APLF [20Al(PO₃)₃–80LiF–PrF₃], BCAYF (19BaF₂–33.25CaF₂–42.75AlF₃–5YF₃–PrF₃), and BCAPLF (19BaF₂–33.25CaF₂–42.75AlF₃–15P₂O₅–20LiF–PrF₃), reveals the effect of the host matrix on the optical properties, particularly the luminescence behavior of Pr³⁺ ions. X-ray absorption near edge structure (XANES) spectroscopy verifies the presence of Pr ions in the glasses with a +3 oxidation state. Absorption spectra results suggest that the lowest energy level of the Pr³⁺ 4f5d configuration is influenced by the oxide/fluoride ratio of the glasses. As both interconfigurational 4f5d and intraconfigurational 4f² transitions are observed, the energy gap between the lowest level of the 4f5d configuration and the overlapping ¹S₀ level of the 4f² configuration is found to influence the predominance of UV emissions from the 4f5d and ¹S₀ levels as well as their decay times. Consequently, a larger 4f5d-¹S₀ energy gap of ∼5000 cm⁻¹ leads to a more intense UV emission from the 4f5d level with a faster decay time. These results underscore the significance of minimizing the energy of the 4f5d level and increasing the gap between 4f5d-¹S₀ levels to be able to obtain fast UV emissions from Pr³⁺-doped fluoride glasses.