Specifically, the main function of adding Y2O3 (yttria) to ZrO2 is to create oxygen ion vacancies and establish a completely stable cubic phase crystal structure. ZrO2 solid electrolyte is essentially an ionic conductor, with its conductivity achieved through the migration of ions facilitated by oxygen ion vacancies within the lattice. The addition of zirconium-based conductive metal oxides induces the formation of a large number of oxygen ion vacancies in the ZrO2 lattice. For every two trivalent yttrium ions (Y3+) introduced, a corresponding oxygen ion vacancy (V?O) is formed. Therefore, the concentration of point defects (vacancies) in the ZrO2 lattice primarily depends on the amount of stabilizer added. The ionic conductivity of ZrO2 is achieved through the directional migration movement of oxygen ions (O2-) between vacancies within its lattice.