Luminescent properties of Tb³⁺ doped sodium silica germanate glasses

Tb³⁺-doped sodium silica germanate glasses were fabricated by conventional melt quenching technique with dopant concentrations of 0.3%mol and 0.9%mol. Their structural characteristics were analyzed through X-ray diffraction and Raman spectroscopy. The study of their optical properties was carried out through steady-state and time-resolved fluorescence spectroscopies. The emission spectra of both glasses are dominated by ⁵D₄ → ⁷F_J manifold transitions. The most intense band, associated with the ⁵D₄ → ⁷F₅ transition, shows a clear split into two peaks (541 nm 550 nm) due to crystal field splitting. The decay of Tb³⁺ emission at 458 nm exhibits a non-exponential evolution accompanied by a shortening of its lifetime as the concentration of Tb³⁺ increases, due to a non-radiative Tb³⁺-Tb³⁺ energy transfer through the cross-relaxation mechanism [⁵D₃, ⁷F₆] → [⁵D₄, ⁷F₀] between two terbium ions. The color coordinates at different excitation wavelengths lie in the yellow-green region of the Commission International de l’Eclairage chromaticity diagram. The results indicate that the studied glasses can be used in applications such as solid-state lighting and display devices.