THE STABILITY OF DEFECTS IN THE CERAMIC INTERFACES, MGO/MGO AND CEO2/AL2O3

We investigate the effect of defects on the stability of ceramic interfaces. We show that a reduced density of ions at the interface is essential for the stability of MgO(100)/MgO(100) twist grain boundaries. Triple layer CeO2 on an Al2O3 support with the Sigma(CeO2(111)(P))/Sigma(alpha-Al2O3(001)(P)) = 7/4 (Theta = 19.1 degrees) interface configuration is shown to exhibit lower oxygen vacancy formation energies compared with the unsupported CeO2. Furthermore, these vacancies are stabilised on approaching the interfacial plane. The presence of the interface, for this system, will therefore promote the migration of oxygen from the interfacial plane to the surface, a process that may be of importance in catalytic reactions. In contrast, for a CeO2 monolayer on Al2O3 with the same interfacial configuration, oxygen vacancies at the interface are less stable than in the corresponding unsupported CeO2.