The self-diffusion of 42K+ was measured (figure 21) in single crystals of KClxKBr1-x solid solutions, where x ranged from zero to unity, at a temperature of 650C. It was found that the diffusion coefficient increased in going from pure KBr (x = 0) to pure KCl (x = 1). The increase with increasing x-value was non-linear, with the maximum value occurring around the middle composition. It was suggested that the enhancement of diffusion in mixed crystals was due mainly to a lowering of the Schottky-defect formation energy.

F.Bénière, V.Hari-Babu: Crystal Lattice Defects and Amorphous Materials, 1987, 15[1-4], 263-70