Measurements were made of the intrinsic ionic conductivity (550 to 800C), of the diffusion of Na tracers (640 to 790C), of Na tracer diffusion in a direct-current electric field (600 to 770C) and of Cl tracers (690 to 770C) in pure crystals. The results could be explained in terms of the contributions to cationic and anionic diffusion which were made by free vacancies and by neutral vacancy pairs. The best fit to all of the available conductivity, diffusion and mobility data furnished expressions of the form:
free vacancies: D (cm2/s) = 182 exp[-2.10(eV)/kT]
vacancy pairs: D (cm2/s) = 1130 exp[-2.35(eV)/kT]
The vacancy pairs accounted for nearly 40% of the Na diffusion at the melting point. The above fit gave an essentially constant anion transport number of 0.34.
Diffusion of Vacancies and Vacancy Pairs in NaCl. V.C.Nelson, R.J.Friauf: Journal of Physics and Chemistry of Solids, 1970, 31[4], 825-43
Table 140
Self-Diffusion of 115mCd in Molten NaCl-CdCl2
CdCl2 (mol%) | T (C) | Do (cm2/s) | Q (kcal/mol) | D1000K (cm2/s) |
100.0 | 607-806 | 1.10 x 10-3 | 6.8 | - |
64.4 | 600-900 | 1.45 x 10-3 | 7.4 | 3.63 x 10-5 |
48.0 | 600-730 | 3.80 x 10-3 | 8.8 | 4.54 x 10-5 |
44.3 | 500-600 | 4.47 x 10-3 | 8.7 | 5.86 x 10-5 |
34.2 | 500-690 | 5.62 x 10-3 | 9.2 | 6.28 x 10-5 |
19.9 | 750-990 | 2.82 x 10-3 | 8.4 | 4.25 x 10-5 |