Enhanced oxide ion conductivity in stabilized δ-Bi2O3

The substitution of Re into Bi2O3 allows stabilization of the δ-Bi2O3 structure by additional substitution of any lanthanide ion to give, for example, phases of composition Bi12.5La1.5ReO24.5. Some of these phases have been found to show exceptionally high oxide ion conductivity at low temperatures, ca 10-3 S cm-1 at 300 °C. The phases show a significant structural difference from other δ-Bi2O3 phases previously reported, with interstitial anion sites displaced further from the ideal fluorite position, (1/4,1/4,1/4).