Formation and growth process of defect clusters in magnesia under ion irradiation

In order to understand the effect of damage cascades on the formation and growth process of dislocation loops in MgO under ion irradiation, in-situ observations of microstructural evolution have been performed with the use of a 400 keV TEM combined with two sets of ion accelerators. In-situ observations under 1000 keV electrons have been also done with the use of high voltage electron microscopy. The 1/2〈110〉{110} type of interstitial dislocation loops are formed under irradiation with various kinds of particles. The minimum necessary dose at which the loops are able to be observed in TEM and their formation and growth rates, strongly depends on the irradiation particles. Such dependences of between kinetic processes on irradiation particles are considered to be influenced not only by the distribution of point defects but also by their stability, that is, the higher density of point defects inside damage cascades or at their periphery results in suppressing the growth of loops due to the enhancement of loop nucleation.