Ba0.5Sr0.5Co0.8Fe0.2O3-δ as a cathode for IT-SOFCs with a GDC interlayer

The chemical compatibility of the Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) with the yttria-stabilized zirconia (YSZ) electrolyte or Gd-doped ceria electrolyte (GDC), as well as that of the GDC with the YSZ electrolyte were examined. It was found that BSCF had a good compatibility with the GDC electrolyte but a poor chemical compatibility with the YSZ electrolyte. The BSCF cathode was adopted for anode-supported YSZ electrolyte cells with and without the application of a 1mum thick GDC buffering layer between the cathode and the YSZ electrolyte. The interfacial reactions of the BSCF with the YSZ electrolyte surface and the GDC coated YSZ surfaces were investigated. The single cells were evaluated by using I-V curve measurements and AC impedance spectroscopy. The results depicted a great improvement in cell performance and a significant decrease in polarization resistance after adding the GDC buffer layer. The optimum firing temperature of the GDC film onto the YSZ film was around 1250 deg C, which led to the maximum power density of 1.56Wcm-2 at 800 deg C using air as oxidant and hydrogen as fuel.