The self-diffusivity of O in monocrystals was studied as a function of the O pressure, at 1100C, by using the gas-solid isotope exchange method. Diffusion annealing was carried out in H2-18H2O atmospheres, and the resultant 18O diffusion profiles were measured by means of secondary ion mass spectrometry. The diffusion coefficients were calculated by
using a solution of Fick's second law which took account of evaporation and exchange at the surface. The results (table 70) showed that O diffusion coefficients at 1100C did not depend upon the O pressure, and the values were smaller than published ones. A comparison with previous data on Cr self-diffusion in the same monocrystals revealed that O diffusion was faster than Cr diffusion.
A.C.S.Sabioni, A.M.Huntz, F.Millot, C.Monty: Philosophical Magazine A, 1992, 66[3], 351-60
Table 67
Grain-Boundary Diffusion of Fe in Polycrystalline Cr2O3
Temperature (C) | PO2(atm) | D (cm2/s) |
740 | 10-4 | 5.9 x 10-12 |
800 | 10-4 | 8.1 x 10-12 |
900 | 10-4 | 1.7 x 10-12 |
1000 | 10-4 | 4.0 x 10-11 |
1000 | 1 | 3.9 x 10-11 |
1100 | 10-4 | 7.5 x 10-10 |
Table 68
Bulk Diffusion (PO2 = 10-4atm) of Fe
in a Cr2O3 Film on Ni70Cr30
Temperature (C) | D (cm2/s) |
720 | 1.2 x 10-19 |
800 | 1.7 x 10-18 |
900 | 1.0 x 10-17 |
Table 69
Grain-Boundary Diffusion (PO2 = 10-4atm) of Fe
in a Cr2O3 Film on Ni70Cr30
Temperature (C) | D (cm2/s) |
720 | 3.1 x 10-14 |
800 | 2.5 x 10-13 |
900 | 3.0 x 10-12 |