The contributing factors for the conductivity enhancement in Na4Zr2Si3O12 by the dispersion of SbF5/(SiO2-Al2O3) have been confirmed. Theoretical estimations of the enhanced conductivity based on the space-charge formation and interfacial acid-base interaction showed lower conductivity than the observed conductivity of the composite. This means that the obtained enhancement includes the chemical and structural contributions of dispersed solid superacid particles such as change of density, crystal structure of the matrix, grain size and induced dislocation. These effects would also result in the formation of ionic defects leading to an increase in conductivity.