Role of Divalent Co-Dopant As Structure Stabilizer in Scandia-Stabilized Zirconia Electrolyte for SOFC

The present investigation reports the role of divalent binary co-dopant (Ca2+) in 11 mol% scandia stabilized zirconia (11SSZ) electrolytes to resolve its severe long-term aging issue for application in solid oxide fuel cells (SOFC). Dense electrolytes were formulated via the solid-state reaction method and their crystal structure was identified by X-ray diffractometer (XRD). To examine total electrical conductivity and its stability in oxidizing and reducing atmosphere DC four-point probe measurement was used. Among all the compositions, 0.2Ca11SSZ demonstrates the highest conductivity of 0.075 S cm-1 at 800 degrees C, with excellent stability of 6.7%/100 h in a reducing (97 vol% H2/3 vol% H2O) atmosphere. However, the presence of 0.5 mol% calcium in 11SSZ results in more than threefold suppression of aging rate compared to undoped11SSZ i.e. 2.19%/200 h in air atmosphere at 800 degrees C. Additionally, the doping of divalent Ca2+ widens the electrolytic domain up to pO2 similar to 10-26 atm at 1000 degrees C compared to state-of-art 8YSZ (pO2 similar to 10-22 atm), with 0.024% linear expansion on phase transition and 172 MPa flexural strength. Convincingly, the excellent structure stability and ionic conductivity of calcium co-doped 11SSZ compared to state-of-the-art electrolytes make them potential candidates to be used as an electrolyte for SOFC application. Addition of divalent cations (Mg2+, Ca2+) in 11 mol% scandia stabilized zirconia.Three-fold less conductivity aging in 0.5Ca11SSZ compare to 11SSZ in air atmosphere.Two-fold less conductivity aging of 0.2Ca11SSZ than 11SSZ in reducing atmosphere.Three-fold higher stable conductivity of 0.2Ca11SSZ than 1Ce10SSZ in wet hydrogen.