Oxygen Diffusion in Mayenite

Oxygen transport in mayenite single crystals was studied by means of 18 O/ 16 O 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 a O 2 = 0.1, and as a function of oxygen activity, 0.01 ≤ a O 2 ≤ 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 (O 2– ) and a slow diffusion process that is attributed to the interstitialcy diffusion of superoxide ions (O 2 – ).