Efficient green upconversion emission in transparent Teo2-Geo2 glass-ceramic obtained by billet extrusion

Transparent Yb3+/Er3+ glass-ceramic was successfully obtained by the extrusion method. The extrusion of oxyfluoride tellurite-germanate glass co-doped with Yb3+ and Er3+ ions at 520˚C resulted in the formation of Ba0.75Er0.25F2.25 nanocrystals, leading to an increase in the upconversion (UC) emission intensity of 35 times in glass-ceramic with respect to the glass. The glass to glass-ceramic transition was confirmed by X-ray diffraction (XRD) and Transmission electron microscope (TEM). Also, the structural changes that occurred during crystallization were assessed using Fourier-transform infrared (FTIR) spectroscopy. Furthermore, the pump power and temperature UC emission dependence of glass and glass-ceramic under 976 nm laser excitation were investigated in detail. The assessments showed that i) two-phonons are involved in the UC process and ii) the temperature has a significant influence over it. The Yb3+/Er3+ codoped glass-ceramic shows relatively high Sα and Sr values in a wide temperature range from 300 to 573 K, presenting the maximal Sα value of 3.50 × 10-3 at 573 K and the maximal Sr value of 6.30 × 10-3 at 364 K. These results suggest that the glass-ceramic is a good candidate for optical applications such as luminescent thermometry.

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The research activity was granted by the National Science Centre, Poland No. 2020/39/D/ST5/ 02287, as well as in part by the “Excellence Initiative - Research University” for the AGH University of Science and Technology grant no. 501.696.7996 D2 L34 ID4844.