This material was selected, for the purpose of obtaining trivalent ionic conduction, due to presence of mobile trivalent cations and a structure which weakened electrostatic interactions, between mobile trivalent ionic species and the framework, as much as possible. Among the rare-earth tungstates, this compound (with its conductivity of 6.5 x 10-5S/cm and 600C and activation energy of 44.1kJ/mol) offered the most suitable size for trivalent ionic conduction; with regard to the relationship between the mobile-ion radius and the lattice volume. The ion-conducting characteristics of the rare earths were studied by means of rare-earth concentration-cell measurements and direct-current electrolysis. The electromotive force measurements, using yttrium tungsten bronzes as electrodes, strongly indicated the possibility of trivalent ionic conduction of the rare earth. The mobile species was shown to be rare-earth ions.

Trivalent Ion Conduction in the Sc2(WO4)3-Type Structure. N.Imanaka, Y.Kobayashi, T.Egawa, S.Tamura, G.Adachi: Materials Science Forum, 1999, 315-317, 331-8