Secondary ion mass spectroscopy and nuclear microprobe analysis were used to measure 18O diffusion profiles. It was found that both methods furnished similar results for O volume diffusivity (1.5 x 10-16 to 3 x 10-16cm2/s) and O intergranular diffusion (4 x 10-21

to 7 x 10-21cm2/s). These Ds values were an order of magnitude smaller than those for the  phase.

C.Mons, G.Moulin, L.Priester, G.Rautureau, E.Beauprez, J.Gosset, P.Trocellier: Materials Science Forum, 1993, 126-128, 379-82