It was recalled that the variation in conductivity in this system, as a function of composition and dispersoid size, differed markedly from that of most other known composite systems. Two maxima instead of one were observed, in the conductivity versus composition plot, at 5.5 and 35mol%Al2O3. The greatest conductivity enhancement was observed for 35mol%Al2O3. The increase was equal to about 20 times at 400C, and to 450 times at 200C. A reduction in alumina particle size, from 0.5 to 0.004μm, did not cause any further increase in conductivity.

Na2SO4-Al2O3 Composite Electrolytes - Some Interesting Observations. A.Jain, S.Saha, P.Gopalan, A.Kulkarni: Materials Research Bulletin, 2000, 35[14-15], 2337-42