White‐Light and Yellow/Blue Photoluminescence Emission Based on Dy 3+ ‐Doped SiO 2 –Gd 2 O 3 Composites

This work attempts to obtain Dy 3+ ‐doped SiO 2 –Gd 2 O 3 by sol–gel process , with a molar ratio of 70Si 4+ –30Gd 3+ and Dy 3+ concentrations of 0.1, 0.3, 0.5, and 1 mol%. Heat treatment at temperatures of 1000°C, 1100°C, 1200°C, and 1300°C have been performed. From XRD , the Gd 2 O 3 cubic phase was observed at 1000°C and 1100°C, at 1200°C also were observed Gd 2 O 3 monoclinic phase, predominant at 1300°C. The band‐gap values vary between 4.4 and 5.3 eV, showing dependence on the crystalline phase. Under UV excitation, emission spectra show bands assigned to the Dy 3+ transitions: 4 F 9/2 → 6 H 15/2 (484 nm), 4 F 9/2 → 6 H 13/2 (572 nm), and 4 F 9/2 → 6 H 11/2 (668 nm). The excitation at 275 nm has shown more effective. The ratio between the most intense emission bands (yellow/blue) show values around 0.84 and 1.63. CIE chromaticity diagrams show color coordinates at blue, yellow, and white regions, as a function of Dy 3+ concentration and heat treatment. The lifetime values of excited state 4 F 9/2 were around 0.20 and 0.69 ms. The morphology of particles changed from spherical to coral‐like shape as a function of heat treatment are observed. The sol–gel process showed to be an interesting route to obtain Dy 3+ ‐doped binary system materials.