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

A series of colorless and transparent (28- x )La 2 O 3 -72Al 2 O 3 : x Tm 3+ ( x  = 0, 1, 1.5, 2, 3) luminescent glasses were successfully prepared by the containerless method. The effects of Tm 3+ substitution on the physical, thermal, optical and photoluminescence properties of La 2 O 3 -Al 2 O 3 glasses were investigated. X-ray diffraction confirmed the amorphous natures of the as-prepared glasses. Excitated at 354 nm, La 2 O 3 -Al 2 O 3 :Tm 3+ glasses emitted blue luminescence at 457 nm, corresponding to the 1 D 2 → 3 F 4 transition of Tm 3+ . These glasses showed high Vicker's hardnesses (7.2–8.8 GPa), and excellent thermal stabilities ( T g : 840–851 °C), which were both augmented with increasing content of Tm 3+ . They also exhibited high transmittances in a wide window ranging from 220 nm to 8.9 μm. In conclusion, the substitution of Tm 2 O 3 for La 2 O 3 increased the Vicker's hardness, thermal stability and transmittance window of La 2 O 3 -Al 2 O 3 glasses, allowing potential applications to optical devices in the visible to infrared region.