Diffusion and ionic conductivity in sodium-β-alumina below room temperature

Sodium tracer diffusivity and ionic conductivity have been measured from room temperature down to -79°C on the same single crystals of sodium-β-alumina of composition 1.23Na2O·11Al2O3. The Haven ratio decreases from 0.35 at room temperature to 0.18 at -79°C. The low value of HR and its temperature dependence can be explained in terms of high correlation effects for ionic diffusion due to large associated defects present at low temperatures. © 1981.