Composites which contained up to 50mol% of alumina were prepared by using conventional and solution-casting methods, and were characterized by means of complex impedance analysis, X-ray diffractometry, differential thermal analysis and scanning electron microscopy. This revealed that the materials were 2-phase in nature. It was found that the dependence of the conductivity upon composition and particle size was consistent with the space-charge theory of conduction. The composites which had been prepared by using the solution casting method exhibited an order-of-magnitude lower conductivity than that of those prepared by using the conventional method. The macroscopic data could be explained in terms of a random resistor network which was based upon the existence of a highly-conductive region due to the generation of excess cation vacancies at the matrix/particle interface.

A.Kumar, K.Shahi: Journal of the Physics and Chemistry of Solids, 1995, 56[2], 215-22