Influence of external β-irradiation in oxide glasses

doi:10.1016/S0022-3093(03)00307-7

Journal of Non-Crystalline Solids

Volume 323, Issues 1–3, 1 August 2003, Pages 200-206

https://doi.org/10.1016/S0022-3093(03)00307-7 Get rights and content

Abstract

Radiation effects in oxide glass as external β-irradiation has been investigated by Raman spectroscopy, Cr³⁺ luminescence and EPR spectroscopy to analyze microstructure evolution. Comparison between simplified and complex glasses (high-level nuclear waste glass analogue) was undertaken. Migration and segregation of sodium have been confirmed on simplified irradiated glasses by a polymerization increase and dissolved oxygen presence. Densification under irradiation has also been demonstrated with the increase of three-membered silicate rings in silicate glass and the decrease of the average Si–O–Si angle in the borosilicate glass. In both glasses, Cr³⁺ crystal field was increased, suggesting a Cr–O length decrease. The complex borosilicate glass responds differently: densification effect and Na segregation were not detected. Under β-irradiation, electron-trapping processes on Cr⁶⁺ occurred, forming Cr⁴⁺ and Cr⁵⁺ species.

Introduction

Radiations from beta and alpha decay can produce structural changes in glasses. In particular, some changes occur in high-level waste glasses submitted to radiation [1], [2]. Therefore, understanding the glass structure change under irradiation is important to predicting the long-term behaviour of this material. Even if radiation effects on SiO₂ structure have been extensively studied [3], [4] and external beta irradiation on six oxides glasses have been recently studied by Boizot et al. [5], [6], to our knowledge, mechanisms in complex glasses are limited. To simulate the β dose irradiation accumulated during nuclear waste storage, external electron irradiation has been performed with a Van de Graaff accelerator.

This paper aims to compare the changes in a complex borosilicate glass having a composition very close to the French nuclear SON68 borosilicate glass with those of simplified borosilicate and silicate glasses. Raman, Cr³⁺ photoluminescence and EPR spectra were investigated. Raman spectroscopy can reveal glasses microstructure changes under radiation [5]. Cr³⁺ plays the role of a local luminescent probe in order to follow the Cr³⁺ crystal field change under radiation. Radiation-induced valence state changes in the glass network are also studied by EPR technique.

Section snippets

Experimental

Two borosilicate (BS1) and (S) silicate glasses were synthesized and doped with chromium while a complex borosilicate glass (BS2) with a composition close to the SON68 glass (Table 1) was fused. Compounds were melted at 1200 °C in a platinum crucible (excepted for S glass where fusion temperature is 1400 °C) then annealed at 520 °C during 1 h in a graphite crucible (this temperature corresponds to T_g+20 °C). Chromium solubility was checked in 1.5% of Cr₂O₃ doped glasses. Small crystals of Cr₂O₃

Raman spectra of β irradiated samples

The spectrum of the irradiated silicate glass (S; 4.6 × 10⁹ Gy) on Fig. 1 shows that bands near 850 and 910 cm⁻¹ disappear after irradiation. These bands are respectively assigned to the Si–O symmetric bond stretching motion of Q⁰ and Q¹ species [7] (Qⁿ species correspond to SiO₄ units with n bridging oxygen [7]). Moreover, the lower frequency spectrum of the irradiated S glass shows an increase of a peak near 600 cm⁻¹ similar to the D₂ ‘defect’ peak of pure silica, corresponding to the

Discussion

Raman experiments indicate that: the average Si–O–Si angle decreases in irradiated BS1 and D₂ species increase in irradiated S glasses. We interpret theses results as indicating a possible densification of simplified irradiated glasses. The increase of D₂ species was previously observed by Bates et al. [4] in SiO₂ irradiated with neutrons, known to be compacted.

Concerning the local luminescent probe Cr³⁺, absorption peak positions ν₁ (⁴A₂ → ⁴T₂) and ν₂ (⁴A₂ → ⁴T₁) are in relation to the ligand

Conclusion

This study has shown different changes in simplified and complex glasses under irradiation. Segregation and migration of sodium was confirmed on irradiated simplified silicate and borosilicate glasses. Densification on simplified samples is also attested with the production of three-membered silicate rings in the 4.6 × 10⁹ Gy silicate glass, the decrease of Si–O–Si average angle in the borosilicate glass as well as the Cr–O length bond in both glasses. Actually, Cr³⁺ crystal field increases with

Acknowledgements

The authors thank P. Jollivet (CEA Marcoule) for the synthesis of glasses. The authors are also indebted to the LSI laboratory for the runs at the Van de Graaff accelerator and to T. Pouthier and S. Guillous of the LSI for preparing β-irradiation experiments.

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Influence of external β-irradiation in oxide glasses

Abstract

Introduction

Section snippets

Experimental

Raman spectra of β irradiated samples

Discussion

Conclusion

Acknowledgements

Nucl. Instrum. and Meth. B

Prog. Nucl. Energy

Nucl. Instrum. and Meth. B

J. Non-Cryst. Solids

Nucl. Instrum. and Meth. B

Solid State Commun.

J. Alloys Compd.

J. Lumin.