Diffusion of iron and cobalt in α-(Fe 0.80Cr 20) 2O 3 and (Fe 0.80Cr 0.20) 3O 4

Abstract

The diffusion coefficients of iron and cobalt in the sintered samples of α-(Fe 0.80Cr 0.20) 2O 3 and (Fe 0.80Cr 0.20) 3O 4 were measured in air at temperatures in the range 1498 to 1673 K and under controlled oxygen partial pressures at 1573 K, respectively. It was found that the diffusion coefficient of cobalt in α-(Fe 0.80Cr 0.20) 2O 3 was about one order of magnitude larger than that of iron, but the diffusion coefficients of iron and cobalt in (Fe 0.80Cr 0.20) 2O 3 were the same within the experimental error. The diffusion coefficients of iron and cobalt in α-(Fe 0.80Cr 0.20) 2O 3 were expressed by the following equations: D Fe = 1.5 × 10 5 exp (−610/RT) and D Co = 9.8 × 10 5 exp (−572/RT) , where the units of D and activation energy are m 2 · s −1 and kJ.mol −1, respectively. The diffusion coefficient of iron in α-(Fe 0.80Cr 0.20) 2O 3 was compared with those of cations in other oxides with corundom structure such as α-Al 2O 3, α-Fe 2O 3 and α-Cr 2O 3.