Conductivity of Al2(WO4)3–WO3 and Al2(WO4)3–Al2O3 Composites

Abstract

Composites of (1 – x)Al₂(WO₄)₃–xWO₃ and (1 – x)Al₂(WO₄)₃–xAl₂O₃ are synthesized and their conductivity is studied as dependent on the temperature and oxygen pressure in the gas phase. The transport numbers of charge carriers are determined using the EMF and Tubandt methods. It is shown that there is a composite effect in the Al₂(WO₄)₃–Al₂O₃ system: when 20–60 mol % of nanodispersed Al₂O₃ is added to Al₂(WO₄)₃, ionic conductivity of the composites increases by 0.5–0.8 orders of magnitude as compared to Al₂(WO₄)₃. The dependence of conductivity of the (1 – x)Al₂(WO₄)₃–xAl₂O₃ composites on the Al₂O₃ content passes through a maximum. Such an effect is typical for composite solid electrolytes and can be explained by an additional contribution of interfaces, where the complex oxide is more disordered. There is no composite effect in the Al₂(WO₄)₃–WO₃ system. When Al₂(WO₄)₃ and WO₃ are mixed, a statistical composite is formed with its conductivity determined by the conductivity of the main phase.