Effect of Bismuth Oxide as Sintering Aid for Gadolinia-doped Ceria at 1050°C

Abstract

Dense GDC electrolytes can work as high ion-conducting material for innovative IT-SOFCs. These electrolytes will be used as a base to develop sulfur resistant anodes using copper oxide and GDC, in order to avoid the use of nickel oxide. An aqueous tape casting process to produce dense gadolinia-doped ceria (GDC) electrolyte was developed. The study developed in three main steps. First, the dispersant concentration was idealized for slurries consisting of only distilled water, an ammonium polyacrylate (PAA) dispersant and ceramic powder (commercial Ce0.9Gd0.1O1.95). By examining the rheological behavior of the slurry, the ideal ratio between the active part of dispersant and powder surface was found to be between 0.15 and 0.30 mg/m2 . Second, starting with the dispersed slurry, fixed amounts of acrylic binder and plasticizer were added and the pH was varied in order to identify the optimum pH interval in which the suspension is stable and no agglomerates form. The ideal pH was found to be between 8 and 9. Finally, the amounts of binder and plasticizer were varied and the suspensions were tape casted (thickness 200 µm) to produce a defect free, smooth and high relative green density (about 50%) tape. SEM observations of samples sintered at 1500 °C showed satisfactory dense section profile (about 95%). Figure 1