Hot corrosion of yttria-stabilized zirconia by liquid antimony and antimony oxide

Direct carbon solid oxide fuel cells (DC-SOFCs) with a liquid Sb anode have many advantages over other types of SOFCs; however, their electrolyte faces corrosion by liquid Sb and Sb2O3. To evaluate the tolerance of the electrolyte to the liquid Sb and Sb2O3, 8 mol.% Y2O3-ZrO2 electrolyte (YSZ) discs are prepared and evaluated at 750 degrees C for up to 100 h in both chemical and electrochemical modes, simulating DC-SOFC operating conditions. In the chemical mode, the corrosion by liquid Sb causes Y dissolution from YSZ into the liquid Sb, while the YSZ experiences a phase transformation from cubic to tetragonal structure and grain boundary crack on the surface. Liquid Sb2O3 is more corrosive than liquid Sb, penetrating additionally the grain boundaries into a depth around 15 mu m. In the electrochemical mode, liquid Sb is separated from YSZ by a layer (similar to 150 mu m) of liquid Sb2O3 formed during cell operation. The liquid Sb2O3 layer so formed corrodes YSZ in the same way as in the chemical mode, but the corrosion is intensified with the presence of a current, resulting in a top porous layer (similar to 15 mu m) on YSZ surface with a grain boundary penetration layer (similar to 100 mu m) underneath.