Synthesis of Porous and Dense Elements of SOFC by Electron Beam Physical Vapor Deposition (EBPVD)

Abstract

EBPVD synthesis of certain elements that constitute the functional components of SOFCs i.e. the porous electrodes and dense electrolyte were examined. Partially stabilized zirconia (YSZ) plus 10 wt % Ni porous electrode elements were produced in the form of thick layers. The microporous structure was formed during non-equilibrium deposition of the vapor phase condensates whose two phases do not appreciably interact in the solid state and resulted from a so-called “shadowing” effect. During initiation subsequent growth of various crystallographic faces of the nuclei at different rates, certain microrelief forms and the faces and microprotrusions screen the adjacent regions of the surface from the vapor flow. This results in microporosity aligned normal to the electrolyte layer and permits fuel molecules to reach the electrolyte interface. Subsequent deposition of a thin dense crack free YSZ electrolyte layer resulted in the synthesis of two of the four operating components, i.e. anode, electrolyte, cathode and interconnects. This high rate vapor condensation synthesis of SOFC elements is in sharp contrast to the current powder technology route that uses tape casting or sintering of expensive colloidal powder. The potential value effectiveness of EBPVD processing appears to make it an attractive alternative to the high cost of powder technology.