Tm3+ doped oxy-fluoride glass-ceramics containing NaLaF4 nano-crystals

Oxy-fluoride glass-ceramics offer a promising alternative as hosting of lanthanide ions, making them suitable for the fabrication of optical devices. In this study, transparent oxy-fluoride glass-ceramics doped with Tm3+ have been obtained from glasses in the system K2O–Na2O–Al2O3–SiO2–LaF3 by heat treatments slightly above the glass transition temperature, Tg. Under that treatment, NaLaF4 nano-crystals with sizes up to 30 nm precipitate. The crystallisation has been studied as a function of the heat treatment by using dilatometry, X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The distribution of Tm3+ between glassy matrix and fluoride nano-crystals has been analysed from photoluminescence spectra.