Study of visible, NIR, and MIR spectroscopic properties of Er3+‐doped tellurite glasses and glass–ceramics

Abstract In this paper, the structural, thermal, optical, and spectroscopic properties of Er 3+ ‐doped tellurite glasses with the composition 68.25TeO 2 –19.5ZnO–9.75X–2.5Er 2 O 3 (in mol%) with X = BaO, Na 2 O, and Bi 2 O 3 are reported. The glasses were prepared using the standard melt quenching method. The investigated glasses exhibit low phonon energy (∼745 cm −1 ) and low glass transition temperature varying between 300 and 350°C depending on the glass composition. The Raman spectra show a regular tellurite structure with variations in the number of bridging and non‐bridging oxygens depending on the glass composition, the Na 2 O and Bi 2 O 3 ‐containing glasses having the most and the least polymerized network, respectively. A thermal treatment of the glasses leads to the formation of crystals, the composition of which depends on the glass composition, as revealed by X‐ray diffraction analysis and confirmed using scanning electron microscope‐energy‐dispersive spectroscopy. The precipitation of Er‐containing crystals in the Na 2 O and BaO‐containing glasses leads to an increase in the intensity of the upconversion emissions. Although the Er 3+ ions remain in the amorphous part of the Bi 2 O 3 ‐containing glass after heat treatment, it is the precipitation of Bi 3.2 Te 0.8 O 6.4 crystals in this glass, which is thought to decrease the distance between the Er 3+ ions leading to an increase in the intensity of the upconversion and mid‐infrared emissions.