Amorphization of ceramic materials by ion beam irradiation

Ion-beam-induced amorphization of a wide variety of ceramic materials has been investigated using in situ TEM with 1.5 MeV Kr+ or Xe+ ions at temperatures between 20 and 1000 K. Except for a few ‘amorphization resistant’ materials which usually have simple crystal structures, most ceramic materials under study amorphized after a fraction of a dpa (displacement per atom) at cryogenic temperatures. In general, critical amorphization dose increases with the irradiation temperature at a rate determined by the kinetics of the amorphization and crystallization processes. Based on a cascade quenching model and an analysis on the structural resistance to recrystallization, a semiempirical parameter which can easily be calculated from both structural and chemical parameters of a material, has been developed to predict the susceptibility of ceramics to amorphization. The calculated results for over ten phases in the Al2O3–MgO–SiO2 system agree quite well with the experimental data. The results for phases in the Al2O3–MgO–SiO2 system have also suggested a parallel in the kinetics between ion-beam-induced amorphization and glass formation. The critical amorphization temperature, above which irradiation-induced amorphization cannot be completed, is found to be closely related to the glass transition temperature. The ratio between glass transition and melting temperatures can also be used to predict the susceptibility of a ceramic material to amorphization, equivalent to the Debye temperature criterion.