Reduction of Eu 3+ to Eu 2+ in aluminoborosilicate glasses under ionizing radiation

Abstract

Eu 2O 3-doped aluminoborosilicate glasses were prepared by melting in air at high temperature (∼1500 °C). It was shown by luminescence and Electron Paramagnetic Resonance (EPR) measurements that both Eu 3+ and Eu 2+ ions can exist simultaneously in the glass matrix studied after glass synthesis as well as after exposure to ionizing radiation. Increase of total Eu 2O 3 concentration leads to the increase of Eu 3+ luminescence intensity while the luminescence intensity of Eu 2+ ions tends to decrease. In contrast the EPR indicates that the amount of Eu 2+ ions in the glass increases with total Eu 2O 3 concentration. The difference in the results of the two spectroscopies is explained in terms of energy transfer from Eu 2+ to Eu 3+ leading to an Eu 2+ luminescence quenching. Irradiation results in the increase of reduced Eu 2+ quantity detected by EPR measurements. It was shown that Eu 2+ ions are located in both high ( g ∼ 4.6) and low symmetry (“U’ spectrum) sites in the structure of aluminoborosilicate glasses. The increase of Eu 2+ content by the increase of the irradiation dose manifests the strong reduction process Eu 3+ → Eu 2+.