Study of formation and sequential relaxation of paramagnetic point defects in electron-irradiated Na-aluminosilicate glasses: Influence of Yb

Impact of rare earth element clusters on the excited state lifetime evolution under irradiation in oxide glasses

“…The composition of these glasses was chosen to study the influence of Yb 3+ clustering on spectroscopic changes. This was motivated by our previous observation of Yb 3+ clustering impact on the thermal recovery of radiation induced paramagnetic point defects [9]. Here, we show that Yb 3+ excited state lifetime decreases at a lower rate as a function of the irradiation dose in glasses with high clusters amount.…”

“…The high clustering in ASI09 and ASI11 glass compositions can be explained by a lower amount of NBO due to an increasing Al 3+ content that must be compensated by Na + ions [2]. We checked by MAS NMR of 27 Al the fourfold coordination of Al 3+ in those glasses [9] in order to exclude any modifications of Al 3+ coordination number. To further probe Yb 3+ environment and clustering, EPR spectra were recorded at 4K (Fig.…”

“…This behavior can be understood by considering that the 2 F 5/2 level is quenched by the defects induced by the irradiation. Indeed, the concentration of paramagnetic point defects induced by irradiation decreases with time, with a slower rate in glasses with higher Yb 3+ clustering [9]. This is explained by the ability of clustered Yb 3+ ions to efficiently trap charges under a stable form during the irradiation process.…”

“…Figure 7 displays the total amount of paramagnetic point defects as a function of irradiation dose. This was determined from double integration of the EPR spectra in the g = 2 region [9]. A plateau (10 5 -3·10 6 Gy) is followed by an increase of defects with increasing dose, and then further followed by a decrease at the highest radiation exposure level.…”

“…8. The precise analysis of paramagnetic defect in those glasses was reported in details elsewhere [9]. In ASI03_Yb5, the lifetime of Yb 3+ excited state 2 F 5/2 is already back to its pre-irradiation value ~2.14 ms after annealing at 244 °C [ Fig.…”