Enhanced Al3+ conduction in Al2(WO4)3–Sc2(MoO4)3 solid solutions

Solid solutions in the system (Al2(WO4)3)1−x(Sc2(MoO4)3)x have been formed and electrically characterized. These compounds are mixed trivalent cation conducting solid electrolytes in which both Al3+ and Sc3+ cations are mobile. However, whether Al3+ or Sc3+ cations represent the main charge carrying species depends on the sample composition. In solid solutions with a low Sc2(MoO4)3 content (x<0.6), the Al3+ cations are the predominant charge carriers whereas Sc3+ cations transport the main electrical current fraction in compounds with x>0.7. In comparison to pure Al2(WO4)3, the electrical conductivity is maximally increased by 22 times in (Al2(WO4)3)0.4(Sc2(MoO4)3)0.6, up to 7.7×10−5 S cm−1 (600°C) with a corresponding activation energy of 76.0 kJ/mol. The trivalent cations are clearly identified as mobile charge carriers which generate the electrical properties within these materials. Neither conductivity contributions by oxygen anions nor by electronic species were observed.