Measurement of oxygen grain boundary diffusion in mullite ceramics by SIMS depth profiling

Abstract

We have measured the oxygen self-diffusivity in mullite ceramics via gas/solid exchange experiments in an atmosphere enriched in the rare stable isotope 18 O . The resulting 18 O isotope depth distributions were measured by SIMS depth profiling. Our investigation showed that grain boundary diffusion coefficients are about five orders of magnitude higher than lattice diffusivities. While the pre-exponential factors differ by about two orders of magnitude, the activation enthalpies in the volume (433±21 kJ/mol) and in the grain boundaries (363±25 kJ/mol) are surprisingly close to each other.