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.