ION IRRADIATION-INDUCED AMORPHIZATION IN THE AL2O3-SIO2 SYSTEM - A COMPARISON WITH GLASS-FORMATION

The ion beam-induced crystalline-to-amorphous transition has been inve stigated for crystalline phases in the Al2O3-SiO2 system: Al2O3, SiO2 (quartz), Al2SiO5 (kyanite, andalusile, sillimanite), and 3Al(2)O(3) . 2SiO(2) (mullite). Xe+ 1.5 MeV was used to irradiate samples at tempe ratures from 15 to 1023 K in situ in a transmission electron microscop e to determine the critical amorphization doses. The susceptibility to amorphization is (highest to lowest): quartz, sillimanite, kyanite, a ndalusite, mullite, and alumina. These data are compared to viscositie s and activation energies for viscous flow of melts in this system. Th e doses required for amorphization by ion irradiation are related to t he viscosities of the melts. The activation energies for irradiation-e nhanced annealing are qualitatively correlated with the activation ene rgies of viscous flow. These results suggest a parallel between ion be am irradiation-induced amorphization and glass formation. Glass-formin g ''ability'' correlates with susceptibility to radiation-induced amor phization. (C) 1997 American Institute of Physics.