Tracer diffusion in the b direction of single crystals was investigated at temperatures ranging from 1121 to 1313K. The diffusivities, as found by determining penetration profiles using secondary ion mass spectrometry, could be described by:

D(m2/s) = 9.9 x 10-2exp[-384.5(kJ/mol)/RT]

and

D(m2/s) = 1.8 x 106exp[-369.2(kJ/mol)/RT]

for bulk and grain boundary diffusion, respectively. A tail region in the 18O diffusion profile was suggested to arise from twin boundaries.

I.Sakaguchi, H.Haneda: Journal of Solid State Chemistry, 1996, 124[1], 195-7