Solid solutions of the form, (1-x)Sc2(WO4)3-xSc2(MoO4)3, were prepared and their ion-conducting characteristics were investigated. It was found that the conductivity increased, and the activation energy decreased linearly, with increasing Mo content. The end-member, Sc2(MoO4)3, exhibited the highest conductivity; which was 2.6 times as high as that of the other end-member. By the use of direct-current electrolysis, the conducting species in this system was identified as being the Sc3+ ion. The enhancement of Sc3+-ion conduction in Sc2(MoO4)3 was attributed to a reduction in the electrostatic interaction between mobile Sc3+ and O2- upon introducing a smaller, Mo6+, ion into the tetrahedral unit of (MO4)2-, where M was W or Mo. The Sc2(MoO4)3 end-member was found to possess the most suitable lattice size for Sc3+ ion migration, and thus exhibited the highest Sc3+ ion conductivity in the system.

Trivalent Sc3+ Ion Conduction in Sc2(WO4)3-Sc2(MoO4)3 Solid Solutions. Y.Okazaki, T.Ueda, S.Tamura, N.Imanaka, G.Adachi: Solid State Ionics, 2000, 136-137, 437-40