Composite mixtures were synthesized, and their ionic conduction characteristics were studied. It was found that the maximum conductivity was attained in the composite, 0.9Sc2(WO4)3-0.1Al2O3. From conductivity measurements performed using various O pressures and polarizations, the mobile species in the composite was deduced to be purely ionic. Oxide anions were also eliminated as possible conducting-ion species. Among the remaining possible cationic species, the mobile ion was verified to be the Sc3+ ion alone. The other cations, W6+ and Al3+, were found to function as lattice-forming ions with oxide anions and insulating-oxide constituents, respectively. It was concluded that a suitable technique for enhancing ionic conducting properties was clearly to form a composite between a trivalent-ion conductor and a refractory-oxide insulator.

Trivalent Scandium Ion Conduction in Scandium Tungstate Alumina Composites. N.Imanaka, Y.Okazaki, Y.Kobayashi, S.Tamura, T.Asano, T.Egawa, G.Adachi: Solid State Ionics, 1999, 126[1-2], 41-6