La1.98Ni04±δ, a new cathode material for solid oxide fuel cell: Impedance spectroscopy study and compatibility with gadolinia-doped ceria and yttria-stabilized zirconia electrolytes

A new SOFC cathode material, La1.98NiO4±δ, was tested in presence of two electrolytes, yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC). XRD analysis showed the absence of undesirable phases at the La1.98NiO4±δ/GDC interface, whereas lanthanum zirconate (La2Zr2O7), an insulating phase, is present between electrode La1.98NiO4±δ and YSZ electrolyte. XPS analysis showed that the oxygen lattice can be present in form of LaO and LaNiO3, which explains the high conductivity for these materials. At temperatures lower than 650 °C, the area specific resistance of the electrodes, measured by electrochemical impedance spectroscopy is significantly inferior when associated to GDC rather than YSZ electrolyte. In addition, in the case of GDC, a lower activation energy of about 0.7 eV was obtained, which could be explained by a higher mobility of oxide ions at the La1.98NiO4±δ/GDC interface compared to the La1.98NiO4±δ/YSZ one.