Compatibility and conductivity of La 2 Ni 1−x Fe x O 4+ δ and LaNi 0·6 Fe 0·4 O 3− δ with GDC electrolyte

The compatibilities and conductivities of K₂NiF₄ typed La₂Ni_0·9Fe_0·1O_4+δ (L₂NF91) and LaNi_0·6Fe_0·4O_3−δ (LNF64) perovskites, promising cathode materials for solid oxide fuel cell, with Gd_0·1Ce_0·9O_1·95 (GDC) electrolyte were investigated. L₂NF91 and LNF64 were synthesised using citrate and modified citrate methods with the calcination temperature of 1000°C for 5 h. The single phased oxides with the average particle sizes of L₂NF91 and LNF64 ∼0·2 μm were obtained. The thermal expansion coefficients of L₂NF91 and LNF64 were 12·7×10⁻⁶ and 13·2×10⁻⁶ K⁻¹ respectively. The mixtures of cathode materials and the electrolytes were heated between 800 and 1200°C to observe the formation of secondary phases at the operation temperatures of solid oxide fuel cell. The X-ray diffraction and scanning electron microscopy–energy dispersive X-ray results indicated that L₂NF91 and LNF64 had good chemical compatibility with GDC from room temperature up to 900°C. Both L₂NF91 and LNF64 showed higher conductivities when in contact with GDC electrolyte than with Zr_0·92Y_0·08O_1·96 electrolyte.