Structural and optical characterizations of sol–gel based fluorides materials: LiGdF4:Eu3+ and LiYF4:Er3+

Sol–gel synthesis of isostructural LiGdF4:Eu3+ and LiYF4:Er3+ crystallized powders is reported. Furthermore, LiGdF4:Eu3+ coatings were also prepared by dip- and spin-coating methods. In all cases, X-rays diffraction measurements were performed to check materials crystalline purity while infrared spectroscopy analyses showed that the organic groups are removed after annealing treatments at 550 °C in F2 atmosphere. This result was emphasized by long radiative decay time of Er3+ ions in LiYF4 (τ = 10.5 ms) attributed to the absence of both organic residues and hydroxide ions. Laser induced emission spectra of LiGdF4:Eu3+ were recorded upon excitation in both 5D2 and 6P5/2 high lying levels of respectively Eu3+ and Gd3+ ions. Eventually fluorescence decays of rare earth ions were measured and compared in both cases.