Comparison between the optical properties of sol–gel process and solid state reaction derived LiYF4:Eu3+ powders

Abstract Sol–gel route has been successfully used to obtain pure LiYF 4 :Eu 3+ 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 F 2 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 Eu 3+ ions were recorded and compared to those of LiYF 4 :Eu 3+ prepared by conventional solid state reaction. In both cases, the results are undoubtedly typical of Eu 3+ emitting center embedded in a unique site of D 2d symmetry. Nevertheless, the sol–gel derived samples exhibit 5 D 0 luminescence decays characterized by longer rise times upon 5 D 2 excitation as well as a larger 5 D 1 / 5 D 0 branching ratio at room temperature or 100 K.