Role of Divalent Co-Dopant as Structure Stabilizer in Scandia-Stabilized Zirconia Electrolyte for SOFC
Lakshya Mathur, Donghwi Shin, Muhammad Pramaditya Garry Hanantyo, Yeon Namgung, Bhupendra Singh, Sivaprakash Sengodan, Sun‐Ju Song
Abstract
The present investigation reports the role of divalent binary co-dopant (Ca 2+ ) 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 °C, with excellent stability of 6.7%/100 h in a reducing (97 vol% H 2 /3 vol% H 2 O) 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 °C. Additionally, the doping of divalent Ca 2+ widens the electrolytic domain up to p O 2 ∼ 10 −26 atm at 1000 °C compared to state-of-art 8YSZ ( p O 2 ∼ 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.