Effect of the Eu³⁺ addition on photoluminescence and microstructure of ZnO - CdO - TeO₂ glasses

In this work, the role of europium doping of glasses formulated in the ternary system ZnO-CdO-TeO₂ is described. The Eu-doped oxide glasses were prepared by the conventional melt-quenching method and by using three different compositions. Structural studies reveal that there exists a good affinity between Cd and some rare earth (RE) ions to form the crystalline phase. The X-ray diffraction (XRD) diagrams display that the structure of these glasses is amorphous and with the increase in CdO content and the compatibility of Eu³⁺, there is a tendency to form nanocrystals of CdTe ₂O₅. The scanning electron microscopic (SEM) observation of their microstructure confirms the presence of phase separation. Differential thermal analysis (DTA) of these glasses showed small exothermic peaks noted around 450°C for the V2 glass and 480°C for V1 and V3 glasses, which could be attributed to the formation of these crystals. The infrared spectra showed a main absorption band around 800-600 cm^-1 corresponding to the Te-O stretching mode in TeO₄ and TeO₃ groups. By optical absorption (OA), the band gap (E_g) for each glass was determined; these values were 3.27, 3.14, and 3.3 eV for the V1-V3 glasses, respectively. Furthermore, the presence of Eu³⁺ was detected in the 370-470 nm short-range wavelengths. The photoluminescence (PL) experiments of the glasses showed light emission due to the following transitions: ⁵D₀ → ⁷F₁,⁵D ₀ → ⁷F₂,⁵D₀ → ⁷F₃, and⁵D₀ → ⁷F₄.