The influence of point defects on the sintering of magnesium oxide

Abstract

In this study, the influence of foreign and native point defects in magnesium oxide on the sintering process is examined. We have introduced dopants into magnesium oxide, with cations that share similar sizes but possess varying charges to minimize the direct impact of strain. The selected foreign cations were as follows: (1) Li¹⁺, an acceptor that enhances the concentration of oxygen vacancies; (2) Sc³⁺, a donor that enhances the concentration of magnesium (metal) vacancies; and (3) Zn²⁺, an isovalent dopant. The results reveal that oxygen vacancies introduced by lithium doping greatly decrease the sintering temperature of magnesium oxide compared to the magnesium vacancies’ effect (scandium doping). Zinc doping was found to increase the surface oxygen vacancies with only a minor effect on the sintering temperature. Enhancing the oxygen vacancy concentration by lithium doping creates an additional mechanism for sintering because the anion sublattice is the backbone of the material, and oxygen ion diffusion is the rate-limiting step. Scandium doping also has a sintering–promoting effect, yet a minor one. The doping factor analysis is considered and implies that aliovalent dopants do not affect the concentration of the fast-diffusing species, which are native vacancy associates.