Quantitative reduction of Eu3+ to Eu2+ by a convenient method using (NH4)2HPO4 for enhancing Mn2+ luminescence in P2O5-B2O3-ZnO-KBr glass

In this study, we propose a novel strategy to reduce Eu 2 O 3 to Eu 2+ in the 34.88P 2 O 5 -13.57B 2 O 3 -34.88ZnO-16.67KBr (PBZB) glass system by introducing (NH 4 ) 2 HPO 4 as a reducing phosphorus source. Photoluminescence (PL), photoluminescence excitation (PLE) spectral and UV–Vis absorption spectral analyses revealed that the emission peak at 325 nm excitation originates from the 4f 6 5d 1 → 4f 7 transition of Eu 2+ , confirming the reduction efficacy of (NH 4 ) 2 HPO 4 . Furthermore, incorporating 7.14 % Mn 2+ into PBZB glass and adjusting the concentration of Eu 2 O 3 demonstrated that Eu 2+ doping significantly enhances the red emission of Mn 2+ at 630 nm. Specifically, when the Eu 2 O 3 concentration is 0.12 mol%, the Mn 2+ emission intensity reaches its peak, with a 32.6 % increase in photoluminescence quantum yield (PLQY). However, further increasing the Eu 2 O 3 concentration leads to a decrease in Mn 2+ emission intensity and the appearance of Eu 3+ emission peaks, indicating a limited reduction capacity. Emission spectrum analysis showed a Eu 3+ reduction rate of 76.09 %. The effective energy transfer mechanism from Eu 2+ to Mn 2+ was verified through spectral overlap and decay curve analysis, with calculated energy transfer efficiency being similar to the PLQY increment. This study simplifies the Eu 3+ reduction process and provides a new method for optimizing Mn 2+ red emission in glass.