Trivalent Sc3+ ion conduction in the Sc2(WO4)3–Sc2(MoO4)3 solid solution

The solid solutions of the (1−x)Sc2(WO4)3−xSc2(MoO4)3 system were synthesized and their ion conducting characteristics were investigated. The electrical conductivity increased and the activation energy decreased linearly with increasing the Mo content. Sc2(MoO4)3 (x=1) showed the highest conductivity of 2.6 times as high as that of Sc2(WO4)3 (x=0). By DC electrolysis, the conducting ion species in this system were identified to be trivalent Sc3+ ion. The enhancement of the Sc3+ ion conduction in Sc2(MoO4)3 is due to the reduction of the electrostatic interaction between mobile Sc3+ and O2− by introducing a smaller Mo6+ ion into the tetrahedral unit of (MO4)2− (M=W, Mo). Sc2(MoO4)3 was found to possess the most suitable lattice size for the Sc3+ ion migration, exhibiting the highest Sc3+ ion conductivity among the (1−x)Sc2(WO4)3−xSc2(MoO4)3 system.