Rare-earth doped glass-ceramics were prepared by heat-treating the precursor germanate glasses. The crystalline phases of the glass-ceramics were assigned to be NaAlGeO4 (NAG) and Mg2GeO4 (MG), and the primary particle sizes were derived to be ~31 and ~32nm, respectively. The secondary particle size of crystal grains was estimated to be ~30µm, and the large grain size is owing to the particles aggregation. Under 254 and 365nm radiation, Sm3+-doped glass-ceramics exhibit orange and reddish-orange fluorescences, and Eu-doped glass-ceramics present red and purplish-red lights, respectively. The investigation results of excitation spectra indicate that the Sm3+- and Eu-doped NAG-MG glass-ceramics can be excited efficiently by commercial UV and blue laser diodes, as well as blue and bluish-green LEDs.

hermodynamic properties including characteristic temperatures and thermal parameters of rare-earth (RE) ions doped lithium-yttrium-aluminium-silicate (LYAS) glasses have been investigated. Glass transition temperature (Tg), onset crystallization temperature (Tx), crystallization temperature (Tc), temperature difference value (DT) and Saad-Poulain criterion (S) in Tm3+/Yb3+ co-doped LYAS glasses are obtained to be 814, 1008, 1043, 194 and 8.34 °C, respectively, and the corresponding values of Sm3+ doped LYAS glasses are derived to be 825, 1002, 1053, 177 and 10.94 °C. Evaluations on thermodynamic properties indicate that LYAS glasses are a promising candidate for drawing optical fibers in the temperature range of 850−950 °C.