Synthesis and characterization of eco-friendly, stable green-emitting Tb³⁺-doped borosilicate glasses using waste silica gel

We present the results of an investigation that aimed to optimize the conversion of silica degradation from silica gel into glasses in hopes of reducing the amount of harmful chemical waste that is released into the environment. Glass samples were created by moderate- temperature melting process at 1200°C, with the system combination of (69-x)B₂O₃–18Li₂O–12BaO–xRSGW-1.0Tb₂O₃, where x = 0, 10, 20, 30, 40, 50 and 60 mol%, and RSGW stands for recovered silica gel waste. The chemical recycled silica gel waste was characterized using x-ray fluorescence (XRF) to determine its chemical composition. The recovered silica gel waste (RSGW) was employed in the manufacturing of glass in the role of a network former due to the considerable amount of SiO₂ that it contains. The optimal concentration of RSGW in the glass matrix is 30 mol% to achieve the highest excitation and emission intensities in photoluminescence and X-ray luminescence. The spectroscopic characteristics of borosilicate glass doped with Tb³⁺ were investigated to show the influence of rare-earth ion additives on the composition, luminescence, and color of the materials. Green emissions of Tb³⁺ (544 nm, ⁵D₄→⁷F₅) was seen in Tb-doped glass when excited at 223 nm, 377 nm (under UV excitation). The color coordinates of the International Commission on Illumination chromaticity show the same shade of green color under different Tb³⁺concentrations (under 377 nm). The results of radioluminescence support the trend observed in the emission spectra. The concentration quenching of Tb₂O₃ in (40-y)B₂O₃–18Li₂O–12BaO–30RSGW-yTb₂O₃ glass is y = 1.0 mol% and suitable for use in light-emitting optoelectronic devices that emit the color green.