Comparison of Ion-Beam Irradiation Effects in X2YO4 Compounds

phases with the olivine (A2VIBIVO4), spinel (AIVB2VIO4), and phenakite structures have been investigated using in situ and high-resolution transmission electron microscopy (HRTEM) over a wide temperature range (20–873 K). At low temperatures (<200 K), the olivine and phenakite are susceptible to radiation-induced amorphization with a criti-cal amorphization dose of 0.2–0.5 displacement per atom (dpa). The critical amorphization dose increases with in-creasing irradiation temperature at varying rates for the various phases, resulting in a distinct critical amorphiza-tion temperature for each phase. For the Mg-Fe series of olivine, the susceptibility to amorphization at higher tem-peratures (room temperature or above) increases with increasing Fe content. Although the spinel phases are, in general, much more resistant to amorphization, a high-pressure metastable spinel phase, g-SiFe2O4, is easily amorphized at doses <0.2 dpa at temperatures below 723 K. This phase decomposes after irradiation at 873 K. At 20 K, complete amorphization of the FeCr2O4 spinel (chromite) is achieved at ~ 4 dpa, but no evidence of amorphization is observed in MgAl2O4 spinel after 5.4 dpa. The distinct dif-ferences in the relative susceptibility of these phases to amorphization are discussed in terms of the structural and chemical controls on the amorphization process