Enhanced tracer self-diffusion coefficient in NaCl-Al2O3 composites

The comparison of the electrical conductivity measured in NaCl single crystals and in NaCl-Al2O3 composites, respectively, shows a strong enhancement due to the presence of the Al2O3 particles. The Na+. self-diffusion shows the same enhancement in the extrinsic range as well as in the intrinsic high temperature region. The correlation factor is derived from the Nernst-Einstein relation. The value f = 0.78 +/- 0.1 shows that the mass transport in the composite proceeds by the same mechanism as in the unmixed ionic crystals, i.e. via Schottky defects in NaCl. The Nernst-Einstein relation is closely verified by involving all the ions of the alkali halide phase, in contrast with the space charge model.