Compositionally continuously graded cathode layers of (Ba _0.5Sr_0.5)(Fe_0.91Al_0.09)O _3-δ-Gd_0.1Ce_0.9O₂ by wet powder spraying technique for solid oxide fuel cells

Compositionally continuously graded cathode layers (CGCLs) of (Ba _0.5Sr_0.5)(Fe_0.91Al_0.09)O _3-δ-Gd_0.1Ce_0.9O₂ (BSFA-GDC) have been constructed by a handy and effective technique called wet powder spraying (WPS). CGCLs exhibit similar thermal expansion coefficient (TEC) value between adjacent thin layers. The continuously graded structure and the well-distributed components of BSFA-GDC cathode are confirmed by morphological characterization with scanning electron microscopy (SEM), and by compositional analysis with energy dispersion X-ray spectrometer (EDS), respectively. The polarization resistance (R_p) of CGCLs with three different thicknesses is investigated by electrochemical impedance spectra (EIS). The EIS results show that CGCLs with a moderate thickness of 20 μm achieve the lowest R_p of 0.301 Ω cm² at 800 C. In addition, anode-supported single cells with the configuration of NiO-YSZ/YSZ/GDC/BSFA-GDC have been fabricated and tested. The cell with the CGCLs thickness of 20 μm reaches the highest output power density of 848 mW cm^-2 at 800 C.