The effect of solids loading on the screen-printing and properties of nickel/scandia-stabilized-zirconia anodes for solid oxide fuel cells

Abstract

Screen-printing is a commonly used technique to fabricate thick film solid oxide fuel cell (SOFC) electrodes, followed by drying and high temperature sintering, and this study focuses on the rheology of such screen-printing inks for SOFC anode fabrication, and in particular on the effect of solids content. Commercially available powders of NiO and scandia stabilized zirconia were used, with average particle sizes of 0.714 and 2.151 μm, respectively. The thixotropy and viscosity of inks increased with increasing solid content. The particle network strength, important to the production of films with good particle connectivity and mechanical strength, also increased as the solids content increased. The complex modulus, G*, (indicative of the overall elasticity and tackiness of the inks) ranged from 500 to 4000 Pa, a range found acceptable for screen-printing. The minimum and maximum acceptable solids content were determined to be 25 and 30 vol% respectively. Inks having solids content outside this range were too liquid like and tacky, respectively, for effective screen-printing. The percentage of ink recovery, indicative of the print quality of the resultant films, also increased with solid content. The relevant properties of the anode films, including mechanical strength, electronic conductivity and electrochemical performance, all improved with increasing solids content as a result of improved particle connectivity, consistent with the conclusions drawn from the rheological study. In summary, from the perspective of ink rheology, screen-printability and performance, inks having 28–30 vol% solids were determined as the most suitable for the production of high quality SOFC anode films with a thickness of around 10 μm.