Novel Sol-Gel Route to Prepare Eu(3+)-Doped 80SiO(2)-20NaGdF(4) Oxyfluoride Glass-Ceramic for Photonic Device Applications

Oxyfluoride glass-ceramics (OxGCs) with the molar composition 80SiO(2)-20(1.5Eu(3+): NaGdF(4)) were prepared with sol-gel following the “pre-crystallised nanoparticles route” with promising optical results. The preparation of 1.5 mol % Eu(3+)-doped NaGdF(4) nanoparticles, named 1.5Eu(3+): NaGdF(4), was optimised and characterised using XRD, FTIR and HRTEM. The structural characterisation of 80SiO(2)-20(1.5Eu(3+): NaGdF(4)) OxGCs prepared from these nanoparticles’ suspension was performed by XRD and FTIR revealing the presence of hexagonal and orthorhombic NaGdF(4) crystalline phases. The optical properties of both nanoparticles’ phases and the related OxGCs were studied by measuring the emission and excitation spectra together with the lifetimes of the (5)D(0) state. The emission spectra obtained by exciting the Eu(3+)-O(2−) charge transfer band showed similar features in both cases corresponding the higher emission intensity to the (5)D(0)→(7)F(2) transition that indicates a non-centrosymmetric site for Eu(3+) ions. Moreover, time-resolved fluorescence line-narrowed emission spectra were performed at a low temperature in OxGCs to obtain information about the site symmetry of Eu(3+) in this matrix. The results show that this processing method is promising for preparing transparent OxGCs coatings for photonic applications.