PNNL

Abstract

SOFCs operating at reduced temperatures (800?C or less) require a thin (*25 microns) YSZ electrolyte membrane in order to minimize ohmic losses within the cell. Such a thin membrane cannot be self-supporting, so the electrolyte must be fabricated on a supporting electrode structure. In the present study, tape casting, a proven low-cost method of fabricating planar ceramic structures, was used to prepare anode tapes and electrolyte tapes. The resulting anode and electrolyte tapes were laminated together through a combination of heat and pressure, and then co-sintered to form the anode/electrolyte structure. Optimization of the composition of the tapes (accomplished by adjusting a number of variables, including particle size and relative amounts of the constituent powders, size and amount of fugitive phases, and binder content) and sintering conditions was performed in order to eliminate warping and cracking, and to assure high porosity in the anode, and high density in the electrolyte membrane. After sintering the anode/electrolyte structures, cathodes were applied to the electrolyte membranes by screen-printing. After sintering of the cathode, the resulting cells were tested to determine their performance. Direct testing of the current-voltage behavior of the cells allowed their performance to be optimized by evaluating the effect of changes in the composition and morphology of the cathode and anode on cell performance. The performance of these cells has been analyzed using a "one-dimensional," steady-state SOFC model (see abstract submitted by Chick, Stevenson, Meinhardt, and Simner, "Modeling and Performance of Anode-Supported SOFC.").