Thermal stability of Ln_2NiO_(4+δ) (Ln: La, Pr, Nd) and their chemical compatibility with YSZ and GGO solid electrolytes

摘要

Thermal stability and chemical compatibility with electrolyte materials for Solid Oxide Fuel Cells (SOFC) have been studied on Ruddlesden-Popper nickelates Ln_2NiO_(4+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 ℃ in air. Pr_2NiO_(4+δ) (PNO) decomposes after 24 h of annealing at 700 ℃ confirming its instability at these conditions. Evidences of chemical reaction between La_2NiO_(4+δ) (LNO) and both Ce_(0.9)Gd_(0.1)O_(1.96) (CGO) and Zr_(0.92)Y_(0.08)O_(1.96) (YSZ) were observed at 700 and 900 ℃, respectively. No decomposition or chemical reaction with YSZ or CGO were found for Nd_2NiO_(4+δ) (NNO) below 900 ℃. Nevertheless, reactivity with both electrolytes was found for this compound at 1000 ℃. The kinetics of these reactions strongly depends on the microstructure of Ln_2NiO_(4+δ)