Oxygen Transport in Higher-Order Ruddlesden-Popper Phase Materials

A series of Ruddlesden-Popper phase materials – La3PrNi3O10- δ, La2Pr2Ni3O10-δ and LaPr3Ni3O10- δ – were synthesised and investigated by neutron powder diffraction to understand the oxygen defect structure. The thermal expansion coefficient was calculated for all compositions and was found to be in the range of 13.0 - 13.4 × 10-6 ˚C-1, which is compatible with the commonly used electrolyte materials for solid oxide fuel cells. A weak preference for Pr occupying the M(2) site in the rocksalt layer was also observed. The majority of the oxygen vacancies were confined to the perovskite layers with a particular preference for O(1) and O(5) sites at high temperatures observed by neutron diffraction measurements. Further, a preference for a curved oxygen transport pathway around the NiO6 octahedra was observed which agrees with the published literature for these materials.