The diffusion of Cs+ was measured at temperatures of between 300 and 420C (table 7), by using tracer and serial sectioning techniques. The diffusion involved a vacancy mechanism. The Cs+ ions, which were over-sized in comparison with the host Ag+ ions, produced local strains in the AgBr lattice. This led to diffusivities which were larger than those of substitutional Ag+ and partially compensated for the intrinsic curvature in the Arrhenius plot which was expected to result from the non-linear decrease in the Gibbs free energy for Frenkel defect formation with increasing temperature. The diffusivity of Cs+ in AgBr was lower than that in AgCl. This was attributed to the larger size effect in a more compact lattice.

P.A.Cardegna, A.L.Laskar: Physical Review B, 1985, 32[10], 7000-2

 

 

Table 7

Diffusivity of Cs in AgBr

 

Temperature (C)

D (cm2/s)

419.49

1.38 x 10-7

411.57

1.03 x 10-7

396.43

5.92 x 10-8

387.73

4.72 x 10-8

382.87

4.23 x 10-8

366.10

2.62 x 10-8

352.37

1.58 x 10-8

344.26

1.29 x 10-8

330.79

8.78 x 10-9

329.95

8.20 x 10-9

322.20

6.15 x 10-9

315.99

5.34 x 10-9

300.21

2.79 x 10-9