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.

Diffusion of Cesium in Silver Bromide: a Surprising Observation of the Strain Effect due to an Oversize Solute. P.A.Cardegna, A.L.Laskar: Physical Review B, 1985, 32[10], 7000-2

Table 8

Diffusivity of Fe2+ in AgBr