Preparation and performance of solid oxide fuel cells with YSZ/SDC bilayer electrolyte

YSZ (Y₂O₃-stabilized ZrO₂)/SDC (Sm-doped CeO₂) bilayer electrolyte film was successfully fabricated on NiO/YSZ anode substrate using stepwise sintering processing by screen-printing technique. OCVs (open-circuit voltages) of 1.06 V, 1.05 V and 0.88 V were achieved at 750 °C for single cells with bilayer electrolyte of 12 μm-SDC/8 μm-YSZ, 12 μm-SDC/5 μm-YSZ, and 12 μm-SDC/2 μm-YSZ, respectively. Interdiffusion of ions at YSZ/SDC interface and formation of YSZ-SDC solid solution after sintering at 1400 °C for 2 h was investigated. The EDX result suggested that the region for the interdiffusion in a YSZ/SDC bilayer structure was 2.0 μm from the YSZ/SDC interface into the YSZ layer for Sm and Ce, and 0.5 μm into the SDC layer for Zr and Y. The YSZ-SDC solid solution exhibited a low electrical conductivity, which negatively affected the performance of single cell. After two thermal cycles, the maximum power density of the single cell exhibited a significant decrease. The destruction of YSZ/SDC bilayer electrolyte structure was not observed during the thermal cycles.