Cathodes based on rare-earth metal nickelate ferrites prepared from industrial raw materials for solid oxide fuel cells

Abstract

Powders of composite materials based on lanthanum nickelate-ferrite with different contents of lanthanides were synthesized using Ln-Ni-Fe-O (LnNF) mischmetal. The phase composition of the powders was determined by XRD. The crystal structure of the main phase in LnNF obtained using a mischmetal with a high lanthanum content is perovskite-like, while the structure with a high cerium content is fluorite-like. The temperature coefficients of linear expansion of the synthesized materials were determined by dilatometry. The temperature dependences of electric conductivity of the compact samples and porous electrodes from these materials were studied by the DC four-probe method. The electric conductivity of compact samples from materials prepared using the mischmetal with the perovskite-like structure of the main phase exceeds the electric conductivity of the materials based on the mischmetal with a high cerium content by approximately three orders of magnitude. The temperature dependences of polarization conductivity of electrodes in cells with the Ce0.8Sm0.2O1.9 (SDC) electrolyte at 600–900°C in air were studied by impedance spectroscopy. The LnNF electrodes with a perovskite-like crystal structure of the main phase showed high electrochemical activity.