Irradiation of synthetic garnet by heavy ions and α-decay of 244Cm

Garnet, A3B2X3O12, has a structure that can incorporate actinides. Hence, the susceptibility of the garnet structure to radiation damage has been investigated by comparing the results of self-radiation damage from α-decay of 244Cm and a 1 MeV Kr2+ ion irradiation. Gradual amorphization with increasing fluence was observed by X-ray diffraction analysis and in situ transmission electron microscopy. The critical dose, Dc, for an yttrium-aluminum garnet (Y3Al5O12) doped with 3 wt.% 244Cm is calculated to be 0.4 displacements per atom (dpa). While the doses obtained by ion irradiation experiments of garnets with different compositions (Y2.43Nd0.57)(Al4.43Si0.44)O12, (Ca1.64Ce0.41Nd0.42La0.18Pr0.18Sm0.14Gd0.04)Zr1.27Fe3.71O12, and (Ca1.09Gd1.23Ce0.43)Sn1.16Fe3.84O12, varied from 0.29 to 0.55 dpa at room temperature. The similarity in the amorphization dose at room temperature and critical temperature of the different garnet compositions suggest that the radiation response for the garnet structure is structurally constrained, rather than sensitive to composition, which is the case for the pyrochlore structure-type.