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2 Acta Physica Polonica A

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Phase Transformations in Pyrochlores Irradiated with Swift Heavy Ions: Influence of Composition and Chemical Bonding

100%

Sattonnay G. , Thomé L. , Sellami N. , Monnet I. , Grygiel C. , Legros C. , Tetot R.

Acta Physica Polonica A

2013

tom 123

nr 5

862-866

Gd_2Ti_2O_7 and Gd_2Zr_2O_7 pyrochlores were irradiated with swift heavy ions in order to investigate the effects of the chemical composition on the structural changes induced by high electronic excitation. The XRD results show that the structural modifications induced by irradiation with 93 MeV Xe ions are strongly dependent on the sample composition: Gd_2Ti_2O_7 is readily amorphized, whereas Gd_2Zr_2O_7 is transformed into a radiation-resistant anion-deficient fluorite structure. Atomistic simulations with the second-moment tight-binding QEq model allow us to calculate the lattice properties of both Gd_2Ti_2O_7 and Gd_2Zr_2O_7, and also to quantify the degree of covalency and ionicity in these compounds. These calculations clearly show that Gd_2Ti_2O_7 is more covalent than Gd_2Zr_2O_7, thus confirming that the amorphization resistance can be related to the covalent character of insulators.

Damage Accumulation in Nuclear Ceramics

100%

Thomé L. , Moll S. , Jagielski J. , Debelle A. , Garrido F. , Sattonnay G.

Acta Physica Polonica A

2011

tom 120

nr 1

7-12

Ceramics are key engineering materials in many industrial domains. The evaluation of radiation damage in ceramics placed in a radiative environment is a challenging problem for electronic, space and nuclear industries. Ion beams delivered by various types of accelerators are very efficient tools to simulate the interactions involved during the slowing-down of energetic particles. This article presents a review of the radiation effects occurring in nuclear ceramics, with an emphasis on new results concerning the damage build-up. Ions with energies in the keV-GeV range are considered for this study in order to explore both regimes of nuclear collisions (at low energy) and electronic excitations (at high energy). The recovery, by electronic excitation, of the damage created by ballistic collisions (swift heavy ion beam induced epitaxial recrystallization process) is also reported.