It was pointed out that, although the importance of boundary layers in the general behavior of electronic systems had been recognized long ago, the main emphasis had been placed on bulk properties in the case of ionic conduction; especially with regard to the search for super-ionic conductors. It was recalled that the full significance of boundary layers, with respect to ionic conductivity, was first revealed by Liang’s 1973 study of the electrical properties of the 2-phase system, LiI-Al2O3. It had been found that the ionic conduction was anomalously high in comparison with that of the pure phases. The present lengthy review of so-called composite electrolytes summarized the experimental and theoretical approaches which were used in this field. Emphasis was placed on defect chemistry and space charges.

J.Maier: Progress in Solid State Chemistry, 1995, 23[3], 171-263