An atomic diffusion mechanism (so-called voidal diffusion) was proposed, in which N atoms migrated through the lattice by jumping from a 9(e) site to a thermodynamically unstable tetrahedral 18(g) site and thence to a new 9(e) site. For the first time, the anisotropic nature of diffusion and growth kinetics (together with direct observation of the diffusion fields via Bitter domain patterns) were taken into account and used for N diffusivity measurements. It was found that the planar and axial pre-exponential factors were equal to 7.2 x 10-7 and 2.26 x 10-6m2/s, respectively. The activation enthalpy for diffusion was equal to 143kJ/mol.

C.N.Christodoulou, N.Komada: Journal of Applied Physics, 1994, 76[10], 6041-3

 

Table 197

Lattice Diffusion Parameters for 22P in Fe-Si

 

P (at%)

Si (at%)

Phase

Do (m2/s)

E (kJ/mol)

-

-

paramagnetic

2.87 x 10-2

271

-

-

ferromagnetic

1.38 x 101

332

0.16

-

paramagnetic

3.76 x 10-2

275

0.16

-

ferromagnetic

1.08 x 10-1

288

0.18

-

paramagnetic

2.55 x 10-3

247

0.18

-

ferromagnetic

1.06 x 103

359

0.38

-

paramagnetic

8.87 x 10-3

259

0.38

-

ferromagnetic

4.90 x 100

316

0.13

0.96

paramagnetic

8.48 x 10-4

241

0.13

0.96

ferromagnetic

1.80 x 101

329