Correlated EPR and optical study of charge trapping phenomena in tellurite glasses. The role of barium oxide

Tellurite glasses of the compositions TeO₂(60%)-ZnO(40%) and TeO₂(60%)-ZnO(20%)-BaO(20%) were prepared in the bulk form with following grinding into powders. The samples were X-ray irradiated. The created charge trapping centers were studied in both types of samples using electron paramagnetic resonance (EPR) spectroscopy. The O⁻ defect and two types of F⁺ centers were discovered. One of the F⁺ center remained unchanged whereas the other one as well as the O⁻ defect were affected by the presence of BaO. Moreover, photo-, radio- and thermoluminescence (PL, RL, TL, respectively) methods were applied as well. The discovered charge trapping centers have been proven to influence luminescence properties as well – improving them in the TeO₂(60%)-ZnO(40%) and vice versa degrading them in the TeO₂(60%)-ZnO(20%)-BaO(20%) glasses. The effect was even stronger in the grinded samples as compared to the bulk ones. The role of the BaO has been disclosed as supporting oxygen leakage from the host.

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