The tracer diffusion of Fe in polycrystalline samples of the α-phase was studied by using the radioactive isotope, 59Fe. The dependence of the diffusion coefficient upon the S activity and temperature was investigated (figure 6, table 2). It was found that the predominant transport mechanism was volume diffusion which proceeded via point defects, and that the Fe-diffusion rate was higher than the self-diffusion of Mn in manganous sulfide. Overall, the results could be described by:

D (cm2/s) = 4.36 x 10-4 PS1/6 exp[-127(kJ)/RT]

where PS was the S partial pressure.

Tracer Diffusion of Iron in α-MnS Polycrystals. J.Gilewicz-Wolter, M.Wolter: Solid State Communications, 2001, 117[12], 719-22

 

 

 

Table 2

Diffusivity of 59S in MnS

 

Temperature (K)

PS (Pa)

D (cm2/s)

1069

4.3 x 103

1.08 x 10-9

1173

4.3 x 103

4.32 x 10-9

1173

3.0 x 102

2.50 x 10-9

1173

1.5 x 101

1.38 x 10-9

1173

2.5 x 10-9

4.40 x 10-10

1173

9.0 x 10-11

6.80 x 10-10

1258

4.3 x 103

9.27 x 10-9

 

 

 

Figure 6

Diffusivity of 59Fe in MnS