The tracer diffusivity of 18O in dense polycrystalline samples, or in the c-axis direction of monocrystals, was measured at temperatures ranging from 300 to 700C, under an O partial pressure of 1atm. Penetration profiles were obtained by means of secondary ion mass spectrometry. It was found that the results for polycrystalline material (table 21) could be described by:

D (cm2/s) = 1.7 x 10-5 exp[-0.93(eV)/kT]

while the results for c-axis migration (table 22) could be described by:

D (cm2/s) = 0.6 exp[-2.20(eV)/kT]

The ratio of the 2 values was large, and temperature-dependent. It was concluded that diffusion in the ab-plane and the c-axis direction involved different mechanisms.

M.Runde, J.L.Routbort, S.J.Rothman, K.C.Goretta, J.N.Mundy, X.Xu, J.E.Baker: Physical Review B, 1992, 45[13], 7375-82

Table 21

Diffusion of 18O in Polycrystalline Bi2Cu2Sr2CaOx

Table 22

The c-Axis Diffusion of 18O in Monocrystalline Bi2Cu2Sr2CaOx