Densification of an YSZ electrolyte layer prepared by chemical/electrochemical vapor deposition for metal-supported solid oxide fuel cells

A densification process based on chemical/electrochemical vapor deposition (CVD/EVD) was successfully performed to produce a dense and gas-tight YSZ electrolyte on a metal support for solid oxide fuel cell applications. Micro Ni/YSZ (7:3 wt%) was deposited by screen printing and YSZ was deposited by an atmospheric plasma spray (APS) process on a metal support prior to the CVD/EVD refinement process. The initial nitrogen permeation flux through the YSZ layer prepared by the APS process was in the range of 1.8–2.7×10⁻⁷ mol/s cm² at 25 °C, which shows that residual pores/pinholes existed in the YSZ layer. After YSZ density refinement by the CVD/EVD process, a dense and gas-tight YSZ layer can be obtained after five hours of deposition. An additional 4–7 µm of YSZ was observed after the refinement process was finished. The average film growth rate during CVD/EVD was approximately 1.14 µm/h. From XRD analysis, the YSZ layer prepared after CVD/EVD showed a dominant cubic structure; nonetheless, a secondary phase was also observed. From the SEM and elemental mapping analyses, the YSZ layers showed a homogeneous distribution on the surface of the metal support. The present results showed that the CVD/EVD process is capable of refining the YSZ electrolyte density/tightness by plugging residual pores/pinholes, along with increasing the YSZ thickness, for application in metal-supported solid oxide fuel cells.