Influence of Eu₂O₃ on phase crystallization and nanocrystals formation in tellurite glasses

Glasses of the 17ZnO·32CdO·51TeO₂ system doped with Eu₂O₃ (0–0.75 mol per 100 mol of oxides) were obtained. Non-isothermal differential scanning calorimetry (DSC) tests showed that the glass transition temperature varied in the range of 354° to 371 °C with the addition of Eu₂O₃. The samples were exposed to a thermal treatment in a laboratory oven at 420 °C. X-ray diffraction analysis of the treated samples showed crystalline phases of a variety of metallic oxides, the intensities of which decreased as the Eu doping amount in the samples increased. In all samples, the strongest peak corresponded to ZnTeO₃ with a crystallite size of about 36 nm. Fourier Transform Infrared Spectroscopy showed that CdO and ZnO change their role from modifier to a glass former. Raman spectra showed characteristic bands corresponding to γ–TeO₂. The observations suggest that Eu₂O₃ induced structural changes which in turn led to the formation of molecular oxygen in the interstitial network. Deconvolution analysis of Raman spectra and High-Resolution Transmission Electron Microscopy images confirmed the formation of Te₂O₅, ZnTeO₃ and Te nanocrystals. Photoluminescence analysis showed that Eu ions are incorporated as Eu³⁺ and no reduction occurred after heat treatment.