Extended study of the influence of europium doping on phosphate glass

Abstract

The phosphate glasses with various Eu2O3 concentrations (0.1–3.0 w/w%) were synthesized and studied regarding the influence of europium dopant on the properties of irradiated phosphate glasses. During studies, samples were irradiated using two types of ionizing radiation sources (β− and γ), with obtained doses up to 40 kGy. TL studies were investigated using various methods, such as TL response vs. radiation dose and the TMax-Tstop method. To further investigate, if increasing the europium concentration affects the structure of electron traps, Computer Glow Curve Deconvolution studies linked with various heating rates methods were applied –increasing the concentration of dopant does not influence the number and energy of electron traps in irradiated samples. This fact was also supported by the results of the thermoluminescence spectrum – where no additional signals, besides wide signals from native glass were observed. OSL and IRSL studies were also conducted, for OSL we observed quenching of the signals, similar as in the TLD case. For IRSL studies all samples didn't display any signals. Finally, to understand if Eu3+ also has a “protective” effect, decreasing the yield of generating F-centers during irradiation, UV-VIS spectroscopy was used. It was established that samples doped with europium oxide possess ca. 20% lower signals at F-center maximum (at 475 nm), the building-up maximum at 320 nm was observed, characteristic of the absorption band of Eu2+. All data indicate that europium in phosphate glass is taking the role of an efficient electron quencher. This quenching phenomenon occurs in three ways: first (direct) when the ion reduction process (Eu3+→Eu2+) competes with the formation of F-centers, and second (indirect) when during heating electrons coming from F-centers were quenched by near Eu3+ ions. The third mechanism of quenching occurs through the electron's non-radiative transition induced by increased stress in the glass matrix caused by a large ionic radius of the dopant.