STUDY ON MULTI-LAYER COMPOSITE CATHODE FOR SOLID OXIDE FUEL CELLS

A multi-layer composite cathode material has been investigated. The cathode on YSZ electrolyte disk was fabricated by spraying the mixtures with different ratios of La_0.7Sr_0.3MnO₃ (LSM), La-Sr-Co-Fe-O (LSCF) and YSZ for different layers. The preparation process was separated into two steps, the LSM/YSZ layers were sprayed at first and the samples were sintered at 1100°C, then the layers of LSM/LSCF were sprayed and sintered at 900°C-1000°C. XRD results show that the solid reaction between YSZ and perovskite phase has been restrained. There are more pores in the topper layers with LSCF and LSM sintered at lower temperature than the layers with LSM and YSZ sintered at higher temperature. The results of resistance for each layer measured at high temperature show that the conductivity increases with the increasing of LSM and LSCF ratio. However, the thermal expansion coefficient (TEC) increases too. The results of electrochemical measurement show that the material has the better performance than that of LSM and LSCF, the polarization resistance for this sample is about 0.3Ω.cm² at 800°C. The preparing process has been optimized and the best technique condition is to sinter the cathode at 900°C for 4h.