Impact of Bi3+ amounts on the structural, emission, and photometric properties of Eu3+-doped NPZC glasses for reddish-orange light applications

Sodium-phosphate (NPZC) glasses by co-doping of Eu³⁺ with different Bi³⁺ amounts were fabricated via the melt-quenching method. Physical properties like refractive indices, molar volumes, and densities of current co-doped glasses were obtained. No sharp crystalline peaks via XRD (X-ray diffraction) were observed, indicating the amorphous features of the prepared glasses. The FTIR (Fourier transform infrared) spectra of glasses were recorded in the infrared (400–4000 cm⁻¹) and visible (200–600 nm) regions. The cut-off edges (293- 312 nm) and band gap energies (4.23–3.97 eV) of glasses were estimated from the FTIR. Upon 327 nm excitation, co-doped glasses exhibit bluish-green (350–550 nm) of Bi³⁺(³P₁ → ¹S₀) and red 612 nm of Eu³⁺ (⁵D₀ → ⁷F₂). JO (Ω₂ /Ω₄) parameters and R/O ratios of current glasses are studied. The double-exponential formula is accorded to the decay curves of current glasses, and the decrease in lifetime (472˗378 ns) indicates the Bi³⁺ to Eu³⁺ energy transfer (ET). The maximum ET efficiency of co-doped glasses was found to be 45%. The dipole–dipole interaction causes for PL decay, which is proved by Dexter and Reisfeld’s ET formula. The higher emission cross-section (19.15 × 10^–22 cm²) and optical gain (7.45 × 10^–28 cm²s) values of glasses were obtained. Moreover, the reddish-orange emission of co-doped glasses demonstrates a CCT value below 2500 K and a CP value above 75%.