Electrical conduction mechanism of LaNixMe1−xO3−δ (Me = Fe, Mn)

•Electrical conduction mechanism of LaNixMe1−xO3 (Me = Fe, Mn) was investigated.•Hopping conduction model could be applied for conductivity of both specimens.•The difference of Ea due to that of energy level of Fe and Mn was observed.•Hole concentration estimated by iodimetry increases with increasing Ni content.

Electrical conduction mechanism of LaNixFe1−xO3−δ and LaNixMn1−xO3+δ expected as Sr-free new cathode material for solid oxide fuel cells was analyzed. Electrical conduction behaviors of both specimens could be well fitted by small polaron hopping conduction model. The electrical conductivity of LaNixFe1−xO3−δ increased with increasing Ni content, showing agreement with decrease of activation energy for hopping conduction. The decrease of electrical conductivity and increase of activation energy of LaNixMn1−xO3+δ were observed with increasing Ni content for 0.0 ≤ x ≤ 0.4. Further Ni substitution increased electrical conductivity and decreased activation energy for 0.4 ≤ x ≤ 0.6. It was revealed using iodometry that the difference of hole carrier density between LaNixFe1−xO3−δ and LaNixMn1−xO3+δ was small. It was suspected that the origin of the difference of electrical conduction behavior of LaNixFe1−xO3−δ and LaNixMn1-xO3+δ was difference of energy level of eg band composed of Fe 3d or Mn 3d orbitals and their overlapping quantity with O 2p and Ni 3d band.

Graphical abstractCompositional dependence of (a) electrical conductivity and (b) Ea for hopping conduction of LaNixMe1−xO3 (Me = Fe, Mn).Figure optionsDownload full-size imageDownload as PowerPoint slide