Characterization of cation-ordered perovskite oxide LaBaCo_2O_(5-δ) as cathode of intermediate-temperature solid oxide fuel cells

摘要

A-site cation-ordered perovskite oxide LaBaCo_2O_(5-δ) (LBCO) was synthesized and evaluated as a cathode material of intermediate-temperature solid oxide fuel cells (IT-SOFCs). LBCO was structurally stable when calcined at 850 ℃ in air but transformed into cation-disordered structure at 1050 ℃. LBCO showed chemical compatibility with Gd_(0.1)Ce_(0.9)O_(1.95) (GDC) electrolyte at 850℃ and 1000 ℃ in air. Conductivity of LBCO firstly increased slightly with higher temperature to a maximum of 470 S cm~(-1) at ～250℃ and then decreased gradually with further increase in temperature. Electrochemical impedance spectra of the LBCO/GDC/LBCO symmetric cell were measured, and electrode reaction mechanism for the LBCO cathode was analyzed. The electrode polarization resistance of LBCO was mainly contributed by oxygen ionic transfer across the cathode/electrolyte interface and oxygen atom diffusion-electronic charge transfer process. Low area-specific resistances with values ranging from 0.15 n cm~2 at 650℃to 0.0086 Ω cm~2 at 800 ℃ were obtained. These results have demonstrated that the A-site cation-ordered perovskite oxide LBCO is a promising cathode material for IT-SOFCs.