The diffusion of 18O was measured in monocrystalline samples by monitoring the exchange of gaseous oxygen, enriched in 18O, with the crystals. At an oxygen pressure of 50mm, and 1100 to 1500C:

D(cm2/s) = 1.0 x 10-5 exp[-54(kcal/mol)/RT]

M.O'Keeffe, W.J.Moore: Journal of Physical Chemistry, 1961, 65[8], 1438-9