Magnetron sputtered gadolinia-doped ceria diffusion barriers for metal-supported solid oxide fuel cells

• Sputtered gadolinia-doped ceria barriers implemented in metal-based SOFCs.
• Sr diffusion along column boundaries in the barrier layer is observed.
• Tuning deposition parameters makes 0.6 μm GDC effectively stop Sr diffusion.
• Area specific resistance of 0.34 Ω cm2 is achieved for cells operating at 650 °C.

Gadolinia-doped ceria (GDC) thin films are deposited by reactive magnetron sputtering in an industrial-scale setup and implemented as barrier layers between the cathode and electrolyte in metal-based solid oxide fuel cells consisting of a metal support, an electrolyte of ZrO2 co-doped with Sc2O3 and Y2O3 (ScYSZ) and a Sr-doped lanthanum cobalt oxide cathode. In order to optimize the deposition of GDC to obtain high electrochemical performance of the cells, the influence of film thickness and adatom mobility is studied. The adatom mobility is varied by tuning the deposition temperature and substrate bias voltage.A GDC layer thickness of 0.6 μm is found to effectively block Sr diffusion when bias voltage and deposition temperature is tuned to promote dense coatings. The adatom mobility has a large influence on the film density. Low temperature and bias voltage result in underdense column boundaries which function as channels for Sr to diffuse to the GDC–ScYSZ interface. By tuning deposition temperature, bias voltage and film thickness area specific resistances down to 0.34 Ω cm2 are achieved at cell tests performed at an operating temperature of 650 °C.