Ionic Conductivity of Doped Cerium Trifluoride

The electrical conductivities of the tysonite‐type fluorides based on CeF 3 in the sintered state were measured for various aliovalent cation dopants. Doping of difluoride such as CaF 2 , SrF 2 , or BaF 2 up to 5 mole percent made the conductivity increase while the doping of tetrafluoride such as ThF 4 led it to decrease. These facts together with the experimental results of electrolysis indicated that the specimens were fluoride ion conductors resulting from the easy movement of fluoride ion vacancies. The activation energies for conduction at the high temperature range above 250°C were, in general, about 0.25 eV irrespective of divalent dopant species, while those at lower temperatures were 0.28 ∼ 0.50 eV depending on the dopant species. Their conductivities are, in general, higher than those of the LaF 3 ‐ based electrolytes which are also the tysonite‐type fluorides. ( CeF 3 ) 0.95 ( CaF 2 ) 0.05 had the highest conductivity among the tysonite‐type fluorides ever examined.