Solid oxide membrane (SOM) electrolysis process is an eco-friendly process with low energy consumption and low greenhouse gas emissions by using an oxygen ion conductive solid electrolyte as a membrane. For yttria stabilized zirconia as an anode in the SOM process, yttrium is eluted from the zirconia lattice and destabilized under molten fluoride salt, and CeO₂-Y₂O₃-ZrO₂-based electrolytes are being studied to improve corrosion resistance.
We studied oxygen vacancy ordering and corrosion-induced destabilization behavior of 4Ce4YSZ with the addition of ZnO. In the (4Ce4YSZ)_1-x (ZnO)_x powder synthesized by the Sol-gel method, the proportion of cubic crystals increased with the addition of ZnO, but no secondary phase was formed. As for local atomic structure analysis using EXAFS, the Zr-O peak decreased and oxygen vacancies increased as the amount of Zn doping increased and the oxygen vacancies were considered to have formed near the dissolved Zn²⁺ through the calculated coordination number. Conductivity was measured through impedance and higher conductivity was shown as the addition amount of ZnO increased. These results indicate that dissolved ZnO in the zirconia lattice contributed to the formation of oxygen vacancies.
Fluoride molten salt was applied to the specimen to evaluate corrosion resistance. After the corrosion test, monoclinic phase was observed in YSZ, but no monoclinic phase was formed in (4Ce4YSZ)_1-x (ZnO)_x. EDS line scan was performed to confirm the elution of stabilizing agent yttria and ceria, and the intensity of yttrium peaks on the surface decreased at YSZ and (4Ce4YSZ)_1-x (ZnO)_x, which is due to the formation of an yttria depleted layer. In (4Ce4YSZ)_1-x(ZnO)_x, the peak intensity of cerium was kept constant at the surface and no depletion layer was formed, so the phase transformation was suppressed by cerium, and the phase transformation suppression mechanism by cerium will be discussed.