Novel Eu 3+ -Doped Glasses in the MoO 3 -WO 3 -La 2 O 3 -B 2 O 3 System: Preparation, Structure and Photoluminescent Properties.

Novel multicomponent glasses with nominal compositions of (50-x)MoO ₃ :xWO ₃ :25La ₂ O ₃ :25B ₂ O ₃ , x = 0, 10, 20, 30, 40, 50 mol% doped with 3 mol % Eu ₂ O ₃ were prepared using a conventional melt-quenching method. Their structure, thermal behavior and luminescent properties were investigated by Raman spectroscopy, differential thermal analysis and photoluminescence spectroscopy. The optical properties of the glasses were investigated by UV-vis absorption spectroscopy and a determination of the refractive index. Physical parameters such as density, molar volume, oxygen molar volume and oxygen packing density were determined. The glasses are characterized by a high glass transition temperature. Raman analysis revealed that the glass structure is built up mainly from tetrahedral (MoO ₄ ) ^2- and (WO ₄ ) ^2- units providing Raman bands of around 317 cm ^-1 , 341-352 cm ^-1 , 832-820 cm ^-1 and 928-935 cm ^-1 . At the same time, with the replacement of MoO ₃ with WO ₃ some fraction of WO ₆ octahedra are produced, the number of which increases with the increasing WO ₃ content. A strong red emission from the ⁵ D ₀ level of Eu ³⁺ ions was registered under near-UV (397 nm) excitation using the ⁷ F ₀ → ⁵ L ₆ transition of Eu ³⁺ . Photoluminescence (PL) emission gradually increases with increasing WO ₃ content, evidencing that WO ₃ is a more appropriate component than MoO ₃ . The integrated fluorescence intensity ratio R ( ⁵ D ₀ → ⁷ F ₂ / ⁵ D ₀ → ⁷ F ₁ ) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu ³⁺ in non-centrosymmetric sites. All findings suggest that the investigated glasses are potential candidates for red light-emitting phosphors.