Radiation response of nano-crystalline cubic Zirconia: Comparison between nuclear energy loss and electronic energy loss regimes
Résumé
Nano-crystalline stabilizer free cubic Zirconia films were irradiated with 400 keV Kr and 80 MeV Ag ions in order to compare the effects of nuclear collisions and electronic excitations on nano-structured materials. Grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM) measurements reveal that the radiation response of the nano-crystalline films is critically dependent on the type of irradiation i.e. energy dissipation mechanism of the impinging ions. The 400 keV Kr irradiations did not result in major structural changes except little grain growth; whereas, a significant degradation in the crystallinity of the films was observed after the 80 MeV Ag ion irradiations. The opposite behavior under the two types of irradiation is attributed to the presence of large density of grain boundaries in the nano-crystalline films. The grain boundaries act as sinks for the irradiation induced defects (created via collision cascades) in-case of the 400 keV Kr irradiations thereby leading to defect removal and hence excellent radiation tolerance. On the other hand, reduced mobility of electrons and phonons due to scattering from the grain boundaries enhances the temperature and duration of the thermal spike, created upon the 80 MeV Ag irradiations, consequently leading to the formation of the highly damaged state (significant degradation in crystallinity).