Thermal stability of Ln2NiO4+δ (Ln: La, Pr, Nd) and their chemical compatibility with YSZ and CGO solid electrolytes

Thermal stability and chemical compatibility with electrolyte materials for Solid Oxide Fuel Cells (SOFC) have been studied on Ruddlesden-Popper nickelates Ln2NiO4+δ with Ln: La, Pr and Nd. Samples of each composition prepared by three different routes, were characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Different microstructures were achieved by each preparation method. The thermal stability of these compounds was analyzed by annealing all the samples at 700 and 900 °C in air. Pr2NiO4+δ (PNO) decomposes after 24 h of annealing at 700 °C confirming its instability at these conditions. Evidences of chemical reaction between La2NiO4+δ (LNO) and both Ce0.9Gd0.1O1.96 (CGO) and Zr0.92Y0.08O1.96 (YSZ) were observed at 700 and 900 °C, respectively. No decomposition or chemical reaction with YSZ or CGO were found for Nd2NiO4+δ (NNO) below 900 °C. Nevertheless, reactivity with both electrolytes was found for this compound at 1000 °C. The kinetics of these reactions strongly depends on the microstructure of Ln2NiO4+δ.