Ternary co-doped ytterbium-scandium stabilized zirconia electrolyte for solid oxide fuel cells

The present work aims to understand the effect of binary and ternary co-dopant's presence on the ionic mobility and structural stability of stabilized zirconia. To evaluate that, binary co-dopant combinations with Yb³⁺-Sc³⁺ have been opted (Seg[sbnd]I), followed by the addition of ternary co-dopant in the later part (Seg-II). The crystallographic data suggests that all the compositions consist of cubic or tetragonal symmetry of zirconia without any other phases. Moreover, the highly dense morphology and clear grain boundaries suggest the absence of segregation of impurities. Later on, the electrical conductivity of 0.087 S/cm with a degradation of 5.4% in 150 h at 800 °C in air was obtained for x = 0.08 in (Sc₂O₃)_x(Yb₂O₃)_0.1-x (ZrO₂)_0.9. This huge degradation has been suppressed in the Seg-II of this work, by adding various ternary co-dopant with a chemical formula of (M)_0.005(Sc₂O₃)_0.08(Yb₂O₃)_0.02 (ZrO₂)_0.895, Where M = MgO, In₂O₃, Sm₂O₃, CaO. Among various ternary co-dopants, the presence of In³⁺ shows the lowest degradation of 3% in 270 h with a remarkable conductivity of 0.08 S/cm at 800 °C in air. This suppression of aging without affecting much the conductivity and absence of any pO₂ dependency shows the potential of ternary co-doped (In-2Yb8SSZ) stabilized zirconia to be used as an electrolyte for solid oxide fuel cells (SOFCs) applications.