Ion conducting behavior in (Lu1-xMx)2(WO4)3 solid solutions (M = Sm, Ho, Er) with the Sc2(WO4)3 type structure

Solid solutions in the trivalent cationic conducting system (Lu1-xMx)(2)(WO4)(3) (M = Er, Ho, Sm) that crystallize in the Sc-2(WO4)(3) type structure were prepared and their conducting behaviors were characterized electrochemically. The partial replacement of the Lu3+ cation site in (Lu1-xMx)(2)(WO4)(3) by larger M3+ cations caused a crystal lattice expansion. Due to the opened ion-migration pathways, the solid solutions generally exhibited an increased cationic conductivity relative to pure Lu-2(WO4)(3). The ion conductivity can be optimized by substituting the appropriate amount of M3+ into (Lu1-xMx)(2)(WO4)(3) in order to adjust the expansion of the migration pathways for the Lu3+ cations. Furthermore, a relationship between the average ionic radius of the trivalent cations involved and the ionic conductivity was characterized which makes it possible to predict the composition of the optimum ion-conducting compound in each solid solution system with the Sc-2(WO4)(3) type structure.