High hardnesses of Tm3+-doped La2O3-Al2O3 luminescent glasses fabricated by containerless solidification

Abstract A series of colorless and transparent (28-x)La2O3-72Al2O3:xTm3+ (x = 0, 1, 1.5, 2, 3) luminescent glasses were successfully prepared by the containerless method. The effects of Tm3+ substitution on the physical, thermal, optical and photoluminescence properties of La2O3-Al2O3 glasses were investigated. X-ray diffraction confirmed the amorphous natures of the as-prepared glasses. Excitated at 354 nm, La2O3-Al2O3:Tm3+ glasses emitted blue luminescence at 457 nm, corresponding to the 1D2→3F4 transition of Tm3+. These glasses showed high Vicker's hardnesses (7.2–8.8 GPa), and excellent thermal stabilities (Tg: 840–851 °C), which were both augmented with increasing content of Tm3+. They also exhibited high transmittances in a wide window ranging from 220 nm to 8.9 μm. In conclusion, the substitution of Tm2O3 for La2O3 increased the Vicker's hardness, thermal stability and transmittance window of La2O3-Al2O3 glasses, allowing potential applications to optical devices in the visible to infrared region.