COMPOSITION AND PARTICLE-SIZE EFFECTS ON IONIC-CONDUCTION IN KCL-AL2O3 COMPOSITE SOLID ELECTROLYTES

The composite solid electrolytes KCl-xAl2O3 (0 less-than-or-equal-to x less-than-or-equal-to 50 mol%) have been prepared by conventional and solution-casting methods and characterized by means of complex impeda nce analysis, X-ray diffraction (XRD), differential thermal analysis ( DTA) and scanning electron microscopy (SEM). The XRD, DTA and SEM stud ies reveal that the samples are biphasic. The dependence of conductivi ty on composition and particle size is found to be consistent with the space charge theory of conduction. The composites prepared by the sol ution-casting method exhibit about an order-of-magnitude lower conduct ivity than those prepared by the conventional method. Macroscopically, the results are satisfactorily explained on the basis of a random res istor network model that assumes the formation of a highly-conducting space region as a result of generation of excess cation vacancies at t he matrix-particle interface.