Abstract:For the doping technique with single dopant of Sb₂O₃, Ga₂O₃, In₂O₃, AlCl₃, Bi₂O₃ or Sm₂O₃, the dopant concentrations of 10%(molar fraction) were selected for the CeO₂-based oxygen-ion conductors. A wet chemical method by polymerization of polyvinyl-alcohol was performed for the compound preparation. X-ray diffraction analysis result shows that the calcined powders have nanocrystalline structure with grain size less than 40 nm, and the sintered samples have pure single fluorite-type phase in all doped cerium oxides. Impedance measurement results show that the conductivities and activation energies of CeO₂-based oxides depend closely on the dopants. The Sb₂O₃-doped CeO₂ has the largest conductivity and In₂O₃-doped CeO₂ has the lowest one at 200 ℃, the Bi₂O₃-doped oxide shows the highest activation energy and Al₂O₃-doped oxide shows the lowest one. Ionic radii and association enthalpies of dopants were taken account for different conductivities and activation energies of the CeO₂-based oxygen-ion conductors.

Key words: cerium oxides; doping technique; synthesis process; ionic conductivity; enthalpy