In this case, alloying the zirconia with ceria (similar fluorite structure, but 𝑟 -. "# > 𝑟 () "# ), while it does not result in the creation of additional positively charged vacancies, will facilitate the stability of the cubic structure. It has been studied that addition of less than 2% of 𝐶𝑒𝑂 ! brings higher symmetry to the 𝑆𝑐 ! 𝑂 " -𝑍𝑟𝑂 ! system . The ionic radii of 𝑍𝑟 &% , 𝐶𝑒 &% , and 𝑆𝑐 "% are 84, 111, and 87 pm . The presence of a small amount of 𝐶𝑒 &% dopant will decrease in 𝑐 and increase in 𝑎 = 𝑏 lattice parameter in a way that contributes to the stabilization of the unit cell.