Influence of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δMicrostructure on GDC Interlayer Stability and Cation Diffusion across the LSCF/GDC/YSZ Interfaces

The degradation of GDC interlayer is one of the key issues in the long-term stability of LSCF cathode-YSZ electrolyte based solid oxide fuel cells (SOFCs). Here we demonstrate that the cathode microstructure has a strong influence on the stability of GDC interlayer and cation diffusion behavior of LSCF/GDC/YSZ triplets. LSCF was prepared into two distinct morphologies: porous layers by screen-printing and dense layers by pulsed laser deposition (PLD). Dense GDC barriers by PLD were applied to both porous and dense LSCF cathodes. Interdiffusion and microstructural evolution were investigated at temperatures of 800°C to 1000°C in air. At 800°C, both cathodes showed no apparent formation of SrZrO 3 at the GDC/YSZ interface. Instead, SrZrO 3 formed at the LSCF/GDC interface, and was more evident for the porous LSCF annealed at 900°C. At 1000°C, severe cation interdiffusion at the LSCF/GDC interface became remarkable for the porous cathode, which exhibited rapid degradation of the GDC layer accompanied by the severe SrZrO 3 formation; by contrast the dense cathode only showed localized SrZrO 3 grains. The superior barrier stability of GDC in a dense cathode can be related to the air-tight interface which would minimize microstructural degradation occurring near the oxygen/LSCF/GDC triple phase boundary.