Effects of polymer binder in electrolyte slurries and their microtubular SOFC applications

The electrolyte slurry was prepared by mixing Gd-doped CeO₂ (GDC), solvent (ethanol and toluene), a polymer (polyvinyl butyral (PVB)) binder, and a dispersant (an amine system). The slurries were processed by an atomization process and coated on the top of microtubular tubes. A very smooth (with no cracks) electrolyte surface was obtained when the PVB polymer content was 8 wt. % (regular solution); however, a unique natural patchwork-type nanoporous grain boundary was obtained when the polymer content was increased to 16 wt. % (excess solution) in the same slurries. The results of this study show that polymers (binders) can be used not only to fabricate a dense electrolyte but also to generate a nanoporous grain boundary. The fabricated electrolytes have been tested for solid oxide fuel cell (SOFC) applications in the intermediate-temperature region. The microtubular cell with dense electrolytes maintained a high performance even under 600 °C.