The anomalously large excess ionic conductivity displayed by AgCl at high temperatures has been variously interpreted in terms of the onset of a second type of cation interstitialcy mechanism, or alternatively as due to a decrease in the Frenkel-defect formation energy with increasing temperature. A detailed measurement of the temperature dependence of the diffusivity of substitutional sodium-ion tracer in AgCl is here shown quantitatively to confirm the latter of these possibilities.

• Received 19 May 1975

DOI:https://doi.org/10.1103/PhysRevB.12.3473