Structural and optical characterizations of sol-gel based composites constituted of LiGdF₄-Eu³⁺ nanocrystallites dispersed into a silica matrix

The sol-gel process was utilized for preparing fluoride-oxide composites as powders constituted of undoped or Eu³⁺ doped LiGdF₄ nanocrystallites which are embedded in a silica network. Crystallization of the fluoride phase occurs after 700 °C heat treatment under inert atmosphere (Ar) using trifluoroacetic acid as in-situ fluorine source. Formation of well-crystallized and submicronic LiGdF₄ crystallites were evidenced by X-ray diffraction and transmission electron microscopy respectively. Besides emission spectra as well as decay times of Eu³⁺ recorded from SiO₂-LiGdF₄-Eu³⁺ samples are similar to those obtained from single LiGdF₄-Eu³⁺ fluoride emphasizing the formation of well-dispersed and pure fluoride nanocrystallites with a selective incorporation of Eu³⁺ ions inside this latter.