Evaluation of the activation volume from ionic conductivity measurements under pressure in porous materials

A porous (or polycrystalline) dielectric solid is treated as a two-phase he terogeneous system, consisting of an electrolytic conductive matrix and ins ulating inclusions. The conductivity is described by the Bruggeman's approx imation. We derive analytical expressions for the first- and second-order p ressure derivative of the conductance. The correction terms to the activati on volume value and its compressibility are viewed as functions of the elas tic properties of the porous material. The present model is used to interpr et experimental results published recently for polycrystalline insulators a nd compare with a model which has appeared previously. [S0163-1829(98)04647 -5].