The electrical properties of trivalent cation conducting tungstates of Sc-2(WO4)(3)-type structure have been improved by a composite effect using insulating Al2O3. The corresponding composite materials were prepared by the thermal decomposition of special precursor compounds (solid solutions in the M-2(WO4)(3)-Al-2(MoO4)(3) systems (M = Sc, Sc0.8Lu0.2)), which simultaneously produces both ionic conducting grains and insulating particles within an homogeneously distributed mixture. Impedance spectroscopy, polarization methods and DC electrolysis experiments were used to characterize the electrical properties of the resulting M-2(WO4)(3)-Al2O3 (M = Sc, Sc0.8Lu0.2) composite materials in detail. The electrical conductivity is enhanced 2-4 times in comparison with the pure tungstate compounds. The trivalent rare earth cations are clearly identified as mobile charge carriers which are the origin of the electrical properties within these materials. Neither conductivity contributions by oxygen anions nor by electronic species were observed.