Surface Diffusion and Surface Layer in Ceramics

Abstract

Methods of measuring surface diffusion coefficients and related phenomena have been reviewed. These include grain boundary grooving, sinusoidal profile decay, isolated scratch decay, tracer, 18O-exchange reaction, sintering, spheroidization of cylindrical voids, work function, etc. Most of the surface diffusion coefficients of oxides measured by these methods involve Al2O3, MgO and NiO. The activation energies of surface diffusion measured at low temperature were generally smaller than those measured at high temperature. In MgO and NiO, the surface diffusion coefficient of oxygen is slower than that of cations.Methods of measuring surface layer thickness at elevated temperature are also reviewed and the results for oxides are summarized. In general, the surface layer thicknesses measured by solid state reaction are larger than those measured by 18O-exchange reaction.