Secondary Ion Mass Spectroscopy Study of Oxygen‐18 Tracer Diffusion in 2/1‐Mullite Single Crystals

Abstract

Oxygen 18 O tracer diffusion in Czochralski‐grown mullite single crystals is investigated along [010] and [001]. Oxygen diffusion coefficients range between ∼5 × 10 −20 m 2 /s (1250°C) and ∼9 × 10 −18 m 2 /s (1525°C). The data does not show any significant anisotropy. The values of the activation enthalpy (4.5 eV) and of the activation entropy ((3.4 ± 1.6) k B , where k B is the Boltzmann constant) suggest that the atomic transport occurs via thermally activated vacancies.