Electrical conductivity of uranium–antimony oxide catalysts

Abstract

The relative ionic and electronic contributions to the electrical conductivity of a uranium–antimony oxide catalyst and of USbO₅ have been determined from measurements of a.c. and d.c. conductance.

Under inert atmospheres (390–775 K) conduction in the catalyst (predominantly USb₃O₁₀ together with small proportions of Sb₂O₄ and USbO₅) is associated with both electronic and effectively charged atomic point defects. Only electronic conduction occurs in USbO₅. Under oxygen (10–70 kPa, 493–682 K) both materials are n-type semiconductors at higher temperatures, but at lower temperatures semiconducting behaviour varies with the pressure of oxygen. Heating USbO₅ in oxygen induces an ionic contribution to conductivity. Ionic conduction in the catalyst is eliminated by heating in hydrogen or propene at 470 K but is restored by heating in oxygen.

It is suggested that both charged oxygen vacancies and interstitial oxide ions are involved in interactions of gaseous components with uranium–antimony oxides. With alkenes, interstitial oxide ions give rise to the products of selective partial oxidation.