DIFFUSION OF O-18 IN COO IN AIR

The diffusion coefficient of **1**8O in CoO single crystals has been measured in the temperature range of 1100-1500 degree C in air (p//o//2 equals 2 multiplied by 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 equals (86 plus or minus 30)exp( minus 431 plus or minus 5 kJ mol** minus **1/RT) cm**2S** minus **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** minus **1, agree with a theoretical estimate.