It was recalled that point defects and impurities could interact with an extended defect and lead, under thermodynamic equilibrium, to a species concentration in the extended defects that was different to that in the bulk; together with electrical charge phenomena. Such concentrations in the proximity of interfaces could screen the core charge. Redistribution of these entities could then be observed in concentration profiles, indicating segregation. The aim of the present work consisted firstly of studying the segregation and potential of Al, Co and Ce in NiO bicrystal grain boundaries with misorientations of (12¯2)/[011] and (310)/[001]. The problem was considered for dilute solutions as well as real ones. In the latter case, the use of Debye–Hückel theory permitted calculation of the activity coefficients of species whose values had a significant effect upon the variations in the impurity intergranular concentration curves.

Grain Boundary Segregation of Impurities and Point Defects in Ionocovalent Materials - the Case of NiO Bicrystals. S.Benlamari, N.H.Djaballah, D.E.Mekki, C.J.Monty: Materials Science and Engineering C, 2006, 26[2-3], 169-76