Trivalent ion conduction of the Sc-2(WO4)(3)-Lu-2(WO4)(3) system

The trivalent ionic conduction in the Sc-2(WO4)(3)-Lu-2(WO4)(3) solid solut ion, which possesses the Sc-2(WO4)(3)-type structure was investigated. The Sc site substitution in Sc-2(WO4)(3) for larger Lu3+ occurred completely an d the cell volume of the solid solution linearly expanded with increasing t he Lu content. The ionic conductivity of the solid solution system enhanced with increasing the Lu substitution of the Sc site in Sc-2(WO4)(3) up to 5 0 mol%. On the other hand, the conductivity decreased by replacing the Lu s ite in Lu-2(WO4)(3) for Sc3+ UP to 40 mol%. A discontinuity appeared in the relation between the ionic conductivity and the composition of the solid s olution around 50-60 Lu mol% substitution of the Sc site in the Sc-2(WO4)(3 )-type structure. The electrolysis results derive the conclusion that the s olid solution is a Sc3+ and Lu3+ trivalent mixed conductor and the mainly c onducting species is Sc3+ and Lu3+ below and above 50-60 Lu mol%, respectiv ely. (C) 1999 Elsevier Science BN. All rights reserved.