Electron irradjation damage in magnesium oxide

Abstract

High densities of small defect clusters have been observed in MgO irradiated in the high voltage electron microscope. The threshold voltage at nominal room temperature has been determined as 480 ± 10 kV, corresponding to 64 ± 2 eV for the displacement energy of the magnesium ions. This energy is very similar to the value for oxygen ion displacement from optical absorption studies on accelerator irradiated specimens.¹ The similarity of the displacement energy for the two ions is discussed and the values compared with those for other ceramic materials. Calculations of the displacement cross sections show that at 600 kV the rate of production of oxygen ions is a factor ∼1.8 higher than the rate foi magnesium ions, whereas at 1 MV the rates are very similar. The effect of increasing dose and irradiation temperature on the defect clusters has been investigated and the results are compared with neutron irradiation damage in MgO and electron irradiation damage in other materials.