Diffusion of 18O in CoO in air†

Abstract

The diffusion coefficient of 18O in CoO single crystals has been measured in the temperature range of 1100–1500°C in air ( p o 2 = 2 × 10 4 Pa). The penetration profiles were measured by secondary ion mass spectrometry, and diffusion coefficients could be obtained if evaporation of the sample and exchange of the diffusant with the ambient were taken into account. The diffusion coefficient is given by D = (86 ± 30) exp(− 431 ± 5 KJ mol −1 RT ) cm 2s −1 . The activation energy for diffusion agrees with the activation energy obtained from deformation studies. The heat of sublimation calculated from the evaporation rate, 510 kJ mol −1, agrees with a theoretical estimate.