Crystal structure, thermal expansion and electrical conduction behavior of PrNi_1-xFe_xO_3-δ at high temperature

In order to evaluate potential of PrNi_1-xFe_xO_3-δ as new cathode material for solid oxide fuel cells, single phase preparation, crystal structure at various temperatures, thermal expansion property and electrical conduction behavior at high temperature were investigated. Single phase of PrNi_1-xFe_xO_3-δ (0.3 ≤ x ≤ 1.0) with orthorhombic distorted perovskite structure was successfully prepared by Pechini method. No structural phase transition was observed between room temperature and 1000°C in air. Linear thermal expansion coefficient was evaluated to be around 1.16 × 10^-5K^-1, showing fair agreement with that of yttriastabilized zirconia and gadolinia-doped ceria which were frequently employed as electrolyte material. Electrical conductivity of PrNi_1-xFe_xO_3-δ increased with increasing Ni content; however, the conductivity did not exceed that of LaNi_1-xFe_xO_3-δ. From the comparison of activation energy of variable range hopping conduction and Mössbauer spectroscopy between PrNi_1-xFe_xO_3-δ and LaNi_1-xFe_xO_3-δ, it was suggested that hole carrier concentration of PrNi_1-xFe_xO_3-δ was lower than that of LaNi_1-xFe_xO_3-δ owing to variation of valence of Pr ion.