Ionic diffusion via oxygen vacancies and interstitial positions in layered Ruddlesden-Popper nickelates: A high-temperature study

Rare-earth nickelates Ln2NiO4+δ (Ln = La, Pr, Nd) with perovskite-related layered Ruddlesden-Popper (RP) structure are promising mixed ionic-electronic conductors (MIEC) for high-temperature electrochemical applications such as dense MIEC membranes for oxygen separation and oxygen electrodes for solid oxide fuel/electrolysis cells. The objective of the proposed study is to provide an insight on the changes in oxygen diffusion mechanism on a gradual transition from oxygen excess to oxygen deficiency in the RP structure occurring on substitution of lanthanum by strontium in La2-xSrxNiO4+δ. To this end, the neutron diffraction patterns of three compositions (x = 0, 1.0 and 1.6) will be collected at room temperature, 700°C and 900°C and analyzed by a combination of Rietveld analysis and maximum-entropy method to reveal the dominating pathway of oxygen-ion diffusion.