“…Doping zirconia with various cations such as Ca 2+ , Mg 2+ , Sc 3+ , Y 3+ , and some other rare earth metal cations such as Yb 3+ , Gd 3+ , Nd 3+ , and Sm 3+ result in the formation of stabilized zirconia with fcc cubic structure that offers excellent ionic conductivity, particularly above 1000 • C [15]. Introducing certain amounts of the tetragonal gadolinia (Gd 2 O 3 ) into the zirconia structure can create a stable gadolinium zirconate with various cubic, tetragonal, and monoclinic phases offering high ionic conductivity and thermal stability [16,17]. Gadolinium-doped zirconia (GDZ: Gd 2x Zr 2(1−x) O 4-x ) can also be used as a promising alternative top coating material to improve the conductivity and thermochemical stability of YSZ [18,19].…”