The serial sectioning technique was used to study the isotope effect for the diffusion of Na in crystals at temperatures ranging from 589 to 796C (table 146). The isotope effect was found to decrease as the temperature increased (table 147); indicating a vacancy-pair contribution to the self-diffusion of Na in NaCl. This contribution attained 30 to 45% near to the melting point.

S.J.Rothman, N.L.Peterson, A.L.Laskar, L.C.Robinson: Journal of the Physics and Chemistry of Solids, 1972, 33[5], 1061-9

 

 

Table 146

Diffusivity of Na in NaCl

 

Temperature (C)

D (cm2/s)

796.6

1.97 x 10-8

767.1

9.85 x 10-9

751.2

5.83 x 10-9

719.7

3.33 x 10-9

718.8

3.49 x 10-9

683.8

1.25 x 10-9

648.1

4.36 x 10-10

633.7

3.32 x 10-10

627.4

2.90 x 10-10

621.6

1.93 x 10-10

603.8

1.37 x 10-10

602.7

1.39 x 10-10

589.3

8.75 x 10-11

587.4

8.50 x 10-11

 

 

 

Table 147

Isotope Effect for Na Diffusion in NaCl

 

Temperature (C)

E

796.6

0.484

751.2

0.522

718.8

0.574

683.8

0.631

648.1

0.674

633.7

0.604

621.6

0.695

589.3

0.624