Chemical relaxation experiments were performed on magnetite-hercynite solid solutions, (Fe1-xAlx)3-δO4, with x = 0.0, 0.067, 0.133 or 0.20, at 1300 to 1400C (table 89). The vacancy diffusion coefficient decreased markedly with increasing x. The activation energy was found to be equal to 20.8, 33.5, 50.4 and 66.3kcal/mol for x = 0.0, 0.067, 0.133 and 0.20, respectively. A strong dependence upon x was also found. The dependence of the vacancy diffusion coefficient upon x was interpreted as indicating that the jump frequency of cation vacancies decreased upon introducing Al ions.
Vacancy Diffusion in Magnetite-Hercynite Solid Solution. S.Yamauchi, A.Nakamura, T.Shimizu, K.Fueki: Journal of Solid State Chemistry, 1983, 50[1], 20-32
Table 89
Chemical Diffusion in (Fe0.8Al0.2)3-δO4 at 1300C
Initial PO2 (atm) | Final PO2 (atm) | D (cm2/s) |
2.71 x 10-3 | 1.11 x 10-3 | 1.255 x 10-6 |
1.11 x 10-3 | 2.71 x 10-3 | 1.317 x 10-6 |
5.84 x 10-3 | 2.34 x 10-3 | 1.993 x 10-6 |
2.34 x 10-3 | 5.84 x 10-3 | 2.150 x 10-6 |
5.84 x 10-3 | 2.34 x 10-3 | 1.539 x 10-6 |
7.24 x 10-3 | 1.77 x 10-2 | 3.200 x 10-6 |
1.77 x 10-2 | 7.24 x 10-3 | 2.591 x 10-6 |