Investigation of optical and thermal properties in Er3+-doped Ga2O3-La2O3-Ta2O5 glasses fabricated by containerless solidification

Highlights: • Er³⁺-doped gallate-based glasses are prepared by containerless solidification. • The prepared glasses exhibit superior thermal properties as well as excellent down-conversion luminescence properties. • Non-isothermal kinetic analyses are adopted to further assess the thermal stability of the selected glass. • We think the glasses might be the potential promising optical materials for fiber amplifier and laser. -- Abstract: 55Ga₂O₃-(35-x)La₂O₃-10Ta₂O₅-xEr₂O₃ transparent and bulk glasses were successfully synthesized by a containerless processing method. The effects of Er³⁺ concentration on thermal stability and optical properties were studied in detail. The prepared glasses exhibited high glass-transition temperature (T_g> 798 °C) and goodo resistance to crystallization (ΔT > 134 °C) by differential thermal analysis (DTA). Moreover, the detailed crystallization kinetics of 33La₂O₃-55Ga₂O₃-10Ta₂O₅-2Er₂O₃ glass was investigated, and the activation energy (E) and the frequency factor (v) of crystallization were gained by means of Kissinger method. The refractive indices were higher than 1.94 as well as the Abbe numbers were greater than 31. The transmittance spectra showed a wide transparent window ranging from 280 nm to 7.5 µm and the prepared glasses performed high infrared transmittance of nearly 80.5%. Two intense emissions centered at 1535 nm and 2700 nm could be observed when the glasses were excited by a 980 nm laser, corresponding to the Er³⁺ ions: ⁴I_13/2→⁴I_15/2, ⁴I_11/2→⁴I_13/2 transitions, respectively. By fitting the decay curves, the highest lifetime of ⁴I_13/2 level could be evaluated to be 7.49 ms. Finally, a reasonable luminescence mechanism of down-conversion was proposed systematically.