Transparent Er³⁺ doped Ag₂O containing tellurite glass-ceramics

Transparent Er³⁺ doped Ag₂O containing tellurite glass-ceramics were fabricated by melting process followed by a heat treatment at 20 °C above the glass transition temperature of the glass for 2 to 17 h. The effects of the crystallization on the optical and luminescence properties of the glasses are presented and discussed. The precipitation of Bi₄TeO₈ crystal was confirmed in all the glasses, independently of their composition. From the spectroscopic properties, the heat treatment was found to have no impact on the site of the Er³⁺ ions indicating that the Er³⁺ ions remain in the amorphous part of the glass-ceramic. Although Ag nanoparticles could be evidenced using transmission electron microscopy and nonlinear optical imaging, no surface plasmon resonance band of Ag nanoparticles appeared in the absorption spectrum of the heat treated glasses. No enhancement of the NIR emission centered at 1.5 μm was observed probably due to the low concentration of Ag nanoparticles precipitating in the glasses. However, an increase in the intensity of the upconversion and mid-infrared emissions was observed from the glass-ceramics prepared with the low amount of Ag₂O (<1 mol%). As evidenced using Raman spectroscopy, the addition of Ag₂O was found to depolymerize the tellurite network. The precipitation of the Bi₄TeO₈ crystal in the most polymerized glasses is suspected to reduce the Er–Er distances whereas it has no significant impact on the Er–Er distances in glasses with a depolymerized network.