Trivalent ionic conduction was investigated in solid solutions which had the Sc2(WO4)3 structure. Substitution of the larger Lu3+ ion caused the unit-cell volume of the solid solution to increase linearly with increasing Lu content. The ionic conductivity of the solid-solution system increased with increasing Lu substitution, at the Sc sites of Sc2(WO4)3, up to 50mol%. On the other hand, the conductivity was decreased by replacing the Lu in Lu2(WO4)3 with up to 40mol% of Sc3+. A discontinuity appeared, in the relationship between ionic conductivity and composition, at some 50 to 60mol% of Lu substitution at Sc sites in the Sc2(WO4)3 structure. The electrolysis results indicated that the solid solution was a Sc3+ and Lu3+ trivalent mixed conductor, in which the predominant conducting species was Sc3+ below 50 to 60mol%Lu; and Lu3+ above.

Trivalent Ion Conduction of the Sc2(WO4)3-Lu2(WO4)3 System. Y.Kobayashi, T.Egawa, S.Tamura, N.Imanaka, G.Adachi: Solid State Ionics, 1999, 118[3-4], 325-30