Temperature and Ion-Mass Dependence of Amorphization Dose for Ion Beam Irradiated Zircon (ZrSiO₄)

Abstract

The temperature dependence of amorphization dose for zircon under 1.5 MeV Kr ion irradiation has been investigated using the HVEM-Tandem Facility at Argonne National Laboratory. Three regimes were observed in the amorphization dose-temperature curve. In the first regime (15 to 300 K), the critical amorphization dose increased from 3.06 to 4.5 ions/nm2. In the second regime (300 to 473 K), there is little change in the amorphization dose. In the third regime (> 473 K), the amorphization dose increased exponentially to 8.3 ions/nm2 at 913 K. This temperature dependence of amorphization dose can be described by two processes with different activation energies (0.018 and 0.31 eV respectively) which are attributed to close pair recombination in the cascades at low temperatures and radiation-enhanced epitaxial recrystallization at higher temperatures. The upper temperature limit for amorphization of zircon is estimated to be 1100 K. The ion-mass dependence of the amorphization dose (in dpa) has also been discussed in terms of the energy to recoils based on data obtained from He, Ne, Ar, Kr, Xe irradiations and a 238Pu-doped sample.

Ion irradiation-induced amorphization and nano-crystal formation in garnets

“…Zircon shows a two-step dependence of critical dose for amorphization as a function of temperature under 1.5 MeV Kr þ irradiation; below 300 K and above 475 K [24]. The two-step recovery also has been reported for synthetic zircon [25].…”

“…The previously reported dose for zircon is 0.33 (dpa) [24]; thus, the amorphization dose for garnet is less than that of zircon, but of the same order of magnitude at room temperature. The susceptibility of ceramics to amorphization may be evaluated by a consideration of the structural topology [40,41].…”

Energetics of radiation damage in natural zircon (ZrSiO4)

“…In nuclear waste disposal, zircon has been considered as an actinb -a > c Fig. 1, The zircon structure (after Speer 1982) ide-host phase (Harker and Flintoff 1984;Ewing 1981); the a-decay event damage in natural zircons of great age has been compared to the damage observed in Pu-doped zircon (Weber 1990) and ionbeam irradiated zircon (Wang and Ewing 1992;Wang et al 1993). Radionuclide loss from nuclear waste forms has been evaluated using models for Pb-loss from zircon (Gentry et al 1984;Ludwig et al 1984).…”