Crystallization processes of rare-earth doped GdF3 nanocrystals in silicate glass matrix: Dimorphism and photoluminescence properties

Rare-earth doped GdF3 nanocrystals embedded in silica glassy matrix have been prepared by controlled crystallization of the xerogel; the influence of rare-earth ion (Pr, Sm, Eu, Tb, Dy, Er, Yb) and additional Li-codopant on structural and optical properties was discussed. The precipitation of RE-doped GdF3 nanocrystalline phase is the result of Gd-trifluoracetate thermolysis revealed as a strong exothermic peak at around 300 °C. Structural analysis of RE-doped SiO2-GdF3 glass-ceramic sample calcined at 525 °C showed the occurrence of GdF3 nanocrystals of about 25 nm size, showing hexagonal or orthorombic structure depending on the RE-ion. Under UV-light excitation at 273 nm of Gd3+ ions (8S7/2 → 6I13/2,15/2 transition), photoluminescence spectra showed characteristic RE3+ luminescence due to the non-radiative energy transfer between the excited Gd3+ and acceptor RE ions; the highest energy transfer (≅ 80 %) was observed for Tb3+ and lowest (≅ 21 %) for Sm3+.