| 1.5 MeV Xe{dollar}sp+{dollar} irradiations were carried out on phases in the MgO-Al{dollar}sb2{dollar}O{dollar}sb3{dollar}-SiO{dollar}sb2{dollar} system. They include: {dollar}alpha{dollar}-quartz (SiO{dollar}sb2{dollar}), {dollar}alpha{dollar}-alumina (Al{dollar}sb2{dollar}O{dollar}sb3{dollar}), periclase (MgO), sillimanite (Al{dollar}sb2{dollar}SiO{dollar}sb5{dollar}), kyanite (Al{dollar}sb2{dollar}SiO{dollar}sb5{dollar}), andalusite {dollar}rm (Alsb2SiOsb5){dollar}, mullite {dollar}rm (3Alsb2Osb3cdot 2SiOsb2){dollar}, enstatite {dollar}rm (MgSiOsb3){dollar}, cordierite {dollar}rm (Mgsb2Alsb4Sisb5Osb{lcub}18{rcub}){dollar}, and pyrope {dollar}rm (Mgsb3Alsb2Sisb3Osb{lcub}12{rcub}){dollar}. Data from the literature are used for the following phases: spinel {dollar}rm (MgAlsb2Osb4){dollar} and forsterite {dollar}rm (Mgsb2SiOsb4){dollar}. The susceptibilities of the phases to amorphization is ordered as: quartz, cordierite, enstatite, sillimanite, kyanite, andalusite, mullite, pyrope, forsterite, {dollar}alpha{dollar}-alumina, spinel, periclase.; The results are discussed in terms of glass formation. The susceptibility of a material to amorphization is qualitatively related to the ease of glass formation. From experimental amorphization data and viscosity data, the same trends for the variations in the activation energies for viscous flow and for irradiation-enhanced annealing are shown. Increases of viscosities at melting temperatures correlate with the decrease of amorphization doses. These results support the idea of a parallel between irradiation-induced amorphization and glass formation.; Based on the analysis of glass formation from melt, A semi-empirical parameter, S, is derived to evaluate the susceptibility to irradiation-induced amorphization. S is based on three factors: (1) topological connectivity; (2) field strength; and (3) the phase transition temperature of the crystalline phase. The S value is a good measure of structural "resistance" to recrystallization from a melt, which is a necessary condition for amorphization. The sequences of S values and the ease of amorphization of phases in the MgO-{dollar}rm Alsb2Osb3{dollar}-SiO{dollar}sb2{dollar} ternary are in good agreement. The calculated S values are: quartz (10), cordierite (6.46), enstatite (5.71), sillimanite (5.82), kyanite (5.65), andalusite (5.58), mullite (5.42), pyrope (4.56), forsterite (3.93), {dollar}alpha{dollar}-alumina (2.69), spinel (2.67), periclase (1.29).; The similarities between irradiation-induced amorphization and glass formed by quenching from melt are related to the thermal spike model. A detailed model is derived based on the fast quenching and epitaxial crystallization within a molten zone. A unified view of the ion beam-induced amorphization can be obtained through the model. The predicted amorphous volume accumulation with increasing ion dose fit the experimental data on zircon and silicon. The temperature dependence of amorphization dose is also predicted by the model. The success of the model suggests the cascade-quenching hypothesis is a reasonable description of radiation-induced amorphization. |
