Structure and Luminescent Properties of Niobium-Modified ZnO-B₂O₃:Eu³⁺ Glass

The effect of the addition of Nb2O5 (up to 5 mol%) on the structure and luminescent properties of ZnO-B2O3 glass doped with 0.5 mol% (1.32 x 10(22)) Eu2O3 was investigated by applying infrared (IR), Raman and photoluminescence (PL) spectroscopy. Through differential thermal analysis and density measurements, various physical properties such as molar volume, oxygen packing density and glass transition temperature were determined. IR and Raman spectra revealed that niobium ions enter into the base zinc borate glass structure as NbO4 tetrahedra and NbO6 octahedra. A strong red emission from the D-5(0) level of Eu3+ ions was registered under near UV (392 nm) excitation using the F-7(0) -> L-5(6) transition of Eu3+. The integrated fluorescence intensity ratio R (D-5(0) -> F-7(2)/D-5(0) -> F-7(1)) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu3+ in non-centrosymmetric sites. The higher Eu3+ luminescence emission observed in zinc borate glasses containing 1-5 mol% Nb2O5 compared to the Nb2O5-free zinc borate glass evidences that Nb2O5 is an appropriate component for modifying the host glass structure and improving the emission intensity.