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Abstract: 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 =10.5ms) 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. [Copyright &y& Elsevier]

Abstract: Sol–gel route has been successfully used to obtain pure LiYF4:Eu3+ powders for the first time to our best knowledge. Fluorine ions were introduced through trifluoroacetic acid as reacting agent which is decomposed under heating treatment and as a result leads to the formation of fluorides. Sintering under F2 reactive atmosphere was performed to prevent any oxidation and insure residual hydroxide elimination. The materials structure was analyzed by means of X-ray diffraction (XRD) while infrared spectroscopy (IR) was carried out to examine the presence of residual organic groups. Laser induced luminescence spectra as well as fluorescence decays of Eu3+ ions were recorded and compared to those of LiYF4:Eu3+ prepared by conventional solid state reaction. In both cases, the results are undoubtedly typical of Eu3+ emitting center embedded in a unique site of D2d symmetry. Nevertheless, the sol–gel derived samples exhibit 5D0 luminescence decays characterized by longer rise times upon 5D2 excitation as well as a larger 5D1/5D0 branching ratio at room temperature or 100K. [Copyright &y& Elsevier]

Sol–gel route has been successfully used to obtain pure Y3Al5O12 and Y3Al5O12:Eu3+ powders. The formation process, the structure as well as the microstructure of the materials were analyzed by means of X-ray diffraction (XRD), thermal analysis (TG–TDA), infrared spectroscopy (IR) and scanning electron microscopy (SEM). It has been shown that sol–gel derived YAG powders crystallize around 900 °C whereas a temperature much higher is necessary to obtain this compound by solid state synthesis (≈1500 °C). Laser induced luminescence spectra, as well as luminescence decays of Eu3+ ions show undoubtedly the spectral features of a Eu3+ emitting center embedded in a unique site of D2 symmetry. [Copyright &y& Elsevier]