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

Abstract

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 1.8-2.7x 10(-7) mol/s cm(2) at 25 degrees 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 pm of YSZ was observed after the refinement process was finished. The average film growth rate during CVD/EVD was approximately 1.14 mu m/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.