Oxygen Diffusion in Mayenite

Abstract

Oxygen transport in mayenite single crystals was studied by means of 18O/16O isotope exchange experiments and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Oxygen tracer diffusion coefficients D* and oxygen surface exchange coefficients k* were determined as a function of temperature, 773 ≤ T/K ≤ 1273, at an oxygen activity of aO2 = 0.1, and as a function of oxygen activity, 0.01 ≤ aO2 ≤ 0.9, at a temperature of T = 1123 K. Two diffusion processes were observed: a fast diffusion process that is attributed to the interstitialcy diffusion of free oxygen ions (O2–) and a slow diffusion process that is attributed to the interstitialcy diffusion of superoxide ions (O2–).