Abstract
An experimental study of ionic thermocurrents in doped LiF, NaCl, KBr and KI has been carried out in order to study the dependence of the activation parameters with the ionic radius of the impurity Ri. A simple model, which includes lattice distortion around the impurity, has also been developed. This model can explain the different behaviour shown in the activation energy, E, with Ri in these materials (decreasing in LiF and increasing in NaCl, KCl, KBr and KI).