Luminescence properties of Eu³⁺-doped potassium-gadolinium-phosphate glasses

Eu₂O₃-doped K₂O-Gd₂O₃-P₂O₅ glasses were fabricated using the melt-quenching technique. The result indicates that the glasses' density and refractive index increase while the molar volume decreases from 0.05 to 0.5 mol% and then increases from 0.5 to 2 mol% with increased Eu₂O₃ concentration. The absorption spectra in the UV-Vis and NIR regions exhibit an energy transition from a ground state to possible excited states for ⁷F₀ → ⁵K₅, ⁷F₀ → ³P₀, ⁷F₁ → ⁵G₂, ⁷F₀ → ⁵L₆, ⁷F₁ → ⁵D₃, ⁷F₀ → ⁵D₂, ⁷F₁ → ⁵D₁ and ⁷F₀ → ⁷F₆, and ⁷F₁ → ⁷F₆. The luminescence characteristics were examined by photoluminescence (PL) and radioluminescence (RL). Both PL and RL confirmed that the optimum value at 2 mol% of Eu₂O₃ concentration. Similarly, the luminescence efficiency of 2 mol% Eu₂O₃ concentration compared with the BGO crystal equals 16.77%. As the concentration of Eu₂O₃ increased, the experimental decay curve dropped while the energy transfers efficiency (ɳ_ET) and the energy transfer parameter (Q) raised. Interestingly, the CIE of emission spectra under 393 nm (UV lamp) were reddish orange (0.64, 0.35). The branching ratio (β_R) was most significant at 612 nm, and the JO parameter trend was Ω₂ > Ω₆ > Ω₄. Furthermore, all characterizations confirm its applicability in optical display devices.