Oxygen ion conductivity of yttria-niobia mixed oxide with fluoride related structure

The oxygen ion conductivity of Y₂O₃---Nb₂O₅ with a fluorite-like structure was studied. Substitutional solid solutions of Nb₂ O₅ in Y₂O₃ lattice formed the defect fluorite phase and remarkably enhanced the oxygen ion conductivity. Doping with tetravalent cations, especially Ti⁴⁺ or Ce⁴⁺, in yttria-niobia oxide is effective in enhancing the oxygen ion conductivity. Although the n-type semiconducting property appeared below P_O2 = 10⁻¹⁸ atm at 1243 K, the yttria-niobia mixed oxide doped with Ce⁴⁺, Ti⁴⁺, and Zr⁴⁺ stably exhibited oxygen-ion conduction in the wide range of oxygen partial pressures studied.