Positron Annihilation Investigation in Ion-implanted Yttria-stabilized Zirconia
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0908-OO10-01.1
Positron Annihilation Investigation in Ion-implanted Yttria-stabilized Zirconia 1,2
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R.I. Grynszpan , G. Brauer +, W. Anwand
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DGA-DCE-CTA-LOT, 16 bis Av. Pr. de la Côte d’Or, 94114 Arcueil, France SERAM, Ecole Nationale Supérieure d’Arts et Métiers, 75013 Paris, France 3 Forschungszentrum Rossendorf, Postfach 510119, 01314 Dresden, Germany 2
Abstract Implantation with a variety of sub-MeV ions (He, Ar, Xe, O, and I) were performed on cubic single crystals of yttria-stabilized zirconia in order to assess the capability of such material to withstand high fluences as a confinement matrix for nuclear waste. In this work, we confronted the results of both Doppler Broadening using slow positron implantation spectroscopy (DB-SPIS) and the Rutherford Backscattering/Channeling spectroscopy (RBS-C) which are sensitive to lattice defects almost opposite in nature. In spite of their difference in defect specific sensitivity, and except for a precursory damage production stage almost exclusively exhibited by SPIS for very low doses (< 0.1 dpa), either techniques show a similar fluence dependence, which exhibits 3 stages starting respectively around 0.1, 2 and 3 dpa, regardless of the damaging ion. However, owing to the stage I plateau displayed in the variation of the DB-SPIS lineshape parameter, we were able to estimate an ion-mass dependence of the critical size of open-volume defects reached before the production of new predominant defects. Keywords: zirconia, ion-irradiation, positrons, RBS-Channeling + Corresponding author: [email protected]
1 - Introduction The use of zirconia as a confinement matrix of nuclear waste is contemplated in the transmutation processes designed to eliminate long-lived isotopes [1]. In addition to the exposure to high neutron fluxes, ions will be released in the host material (noble-gas ions in particular), owing to the decay of actinides. It is therefore necessary to assess the possible defective consequences of such an external or internal irradiation on in-service properties of zirconia. Although only affecting the near surface of a material, ion beam implantation, which allows the accumulation of high doses in short periods of time, is a common procedure to monitor this aging process [2]. Since open-volume defects resulting from the irradiation are expected to be the prime factor responsible for the degradation of mechanical characteristics, Slow Positron Implantation Spectroscopy (SPIS) seems the most appropriate technique to probe the microstructure of the damaged material [3]. However, the high sensitivity of this technique to the presence of vacancies is generally counterbalanced by the low saturation threshold of its response to defect concentration. Therefore, as the fluence range of interest also encompasses large damage contents, SPIS results are compared with those of Rutherford Backscattering Spectroscopy and Channeling (RBS/C), the latter technique being sensitive to much larger atomic fractions of defects than the former [4]. Nevertheless, in mak
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