Surface reactivity of irradiated magnesium oxide. Effects of dose on defect concentrations, specific surface areas and chemisorption kinetics

Abstract

The e.s.r. signals from F, V and S centres have been measured in MgO over the fast neutron dose range from 5 × 10¹⁶ to 10²⁰ fast neutrons cm^–2. S centres are initially generated at a faster rate (% available sites per unit dose) than F centres but saturation concentrations of these isolated defects are similar. The specific surface areas of some MgO powders increase on neutron irradiation and this effect has been ascribed to a fragmentation of aggregates at grain boundaries. The fresh surfaces thus produced can play an important role in the radiation-induced reactivity of MgO towards oxygen. The height of the charge barrier produced by reaction of oxygen with F centres has been inferred from the chemisorption kinetics and is shown to be inversely proportional to the F centre concentration, in agreement with theory.