Radiation Induced Structural Changes in Normal Spinels
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1043-T03-03
Radiation Induced Structural Changes in Normal Spinels David Simeone1, Gianguido Baldinozzi2, Dominique Gosset3, Leo Mazerolles4, and Lionel Thome5 1 CEA, Materiaux Fonctionnels pour l Energie, Equipe Mixte CEA-CNRS-ECP, DEN/DMN/SRMA/LA2M, CEN Saclay, Gif sur yvette, 91191, France 2 CNRS, Materiaux Fonctionnels pour l'Energie, CNRS-CEA-ECP, Laboratoire SPMS, Ecole Centrale de Paris, Chatenay Malabry, 92292, France 3 CEA, Materiaux Fonctionnels pour l'Energie, CEA-CNRS-ECP, DEN/DMN/SRMA/LA2M, CEN Saclay, Gif sur yvette, 91191, France 4 CNRS, Institut des Sciences Chimiques Seine Amont, Thiais, 92000, France 5 CNRS, CSNSM Orsay, Université Paris XI, Orsay, 91400, France ABSTRACT Ion irradiation induced phase transformations in three normal spinel compounds MgAl2O4, MgCr2O4 and ZnAl2O4 have been investigated by X-ray diffraction, Raman spectroscopy and Transmission Electron Microscopy. This work presents a unified framework to describe the radiation effects in these spinels. Irradiation modifies the atomic and mesoscopic structures of theses spinels in different ways. At the atomic scale, radiation damages act like the temperature and only produce the inversion of different cations. At the mesoscopic scale, they produce microdomains, responsible for important changes in the X-ray diffraction patterns. INTRODUCTION There has been growing interest in recent years in radiation tolerant ceramics with potential applications that range from nuclear wastes storage (oxides), to new generation of nuclear reactors (carbides). One of the principal factors to select ceramics for nuclear application is its susceptibility to detrimental radiation damages1. Collisions processes occurring during the slowing down of high and low energy incident particles in solids are able to eject many atoms from their equilibrium positions over an important length (few nanometers for low energy particles and few microns for high energy particles). Under irradiation, new metastable phases2 can be produced. They result from the balance between the radiation induced3,4 atomic defects production due to nuclear or electronic collisions and their annihilation due to the thermal diffusion. If the accumulation of atomic defects produced by the slowing down of recoils occurs, crystalline ceramics succumb to an amorphization transformation5 often associated with an important swelling and microcracking. In many simple oxides like MgO and Al2O3, interstitials and vacancies can migrate to form dislocation loops and voids6. On the other hand, MgAl2O4 spinel resulting from a mixture of these two compounds does not exhibit the same behavior7,8,9. Even if dislocations loops are created during irradiation in this oxide8, no void swelling has been reported after high9 and low energy irradiations8. Irradiated by low energy ions at cryogenic temperature7,8 or by high energy ions9 at room temperature, x ray diffraction patterns exhibit a large decreasing of odd Bragg reflexions in this solid. Increasing the temperature of irradiation or the number of incident
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