The migration of small homovalent cations in the monocrystalline material was studied by using tracer/sectioning methods. It was found that the results (table 253) could be described by the expression:

D (cm2/s) = 74.4 exp[-34.94(kcal/mol)/RT]

The temperature dependence of the isotope effect for 22Na and 24Na (table 254) was described by:

E = 126 exp[-13.3(kcal/mol)/RT]

It was concluded that the diffusion behavior of the cations was in good agreement with the so-called displaced homovalent small-radius cation model.

S.M.Klotsman, I.P.Polikarpova, G.N.Tatarinova, A.N.Timofeev: Physical Review B, 1988, 38[11], 7765-76

 

 

Table 253

Diffusivity of 22Na in CsI

 

Temperature (K)

D (cm2/s)

400.1

3.613 x 10-10

420.3

7.923 x 10-10

424.1

9.436 x 10-10

447.0

2.095 x 10-9

494.2

8.777 x 10-9

531.3

2.140 x 10-8

594.2

1.163 x 10-7

611.2

1.928 x 10-7

616.8

2.266 x 10-7

 

 

 

Table 254

Isotope Effect for Na in CsI

 

Temperature (C)

D (22Na)/D(24Na)-1

601.5

0.0034

599.3

0.0026

592.3

0.0026

551.3

0.0019

550.3

0.0014

550.5

0.0012

500.8

0.0018

450.1

0.0005