Impact of Nb2O5 on the Glass Structure and Quantum Efficiency of Eu3+–doped Phosphate Glasses

Abstract

This work investigates the influence of Nb2O5 incorporation on the structural and luminescent properties of Eu3+–doped phosphate glasses. Raman spectroscopy revealed that the addition of Nb2O5 promotes the substitution of PO4 units by NbO6 octahedra, leading to depolymerization of the glass network and a reduction in phonon energy. Optical absorption spectra showed a redshift in the absorption edge and a decrease in the optical band gap, associated with an increased number of nonbonding oxygens. Photoluminescence spectra exhibited an enhancement in the hypersensitive 5D0 → 7F2 transition and increases in both the relative intensity ratio (R) and the Judd–Ofelt parameter Ω2, indicating a rise in local asymmetry. Lifetime measurements revealed a reduction in the experimental lifetime, along with an increase in total radiative emission rate and suppression of non–radiative processes, yielding a quantum efficiency of up to 93%. These findings demonstrate that Nb2O5 incorporation significantly improves the red emission efficiency of Eu3+ ions in phosphate glass matrices.