Phase formation and ionic conductivity studies on ytterbia co-doped scandia stabilized zirconia (0.9ZrO2–0.09Sc2O3–0.01Yb2O3) electrolyte for SOFCs

The effect of ytterbia co-doping in scandia stabilized zirconia (ScSZ) on phase formation and electrical conductivity was studied. The ternary (ZrO2)0.90 (Sc2O3)0.09 (Yb2O3)0.01 composition was prepared by solution combustion synthesis. The powder was characterized by X-ray diffraction, scanning and transmission electron microscopy. The processed powder of the co-doped sample was found to be nanocrystalline and it exhibited a single cubic phase. The powder was compacted in to disc and sintered to produce a dense electrolyte pellet. X-ray diffraction analysis showed that the cubic phase remains after sintering in the co-doped sample whereas peaks corresponding to the rhombohedral β phase appear in the sintered binary (without co-doping) scandia stabilized zirconia (ScSZ) sample. The electrical conductivity was measured as a function of temperature by impedance spectroscopy. The electrical conductivity of the ytterbia co-doped sample was found to be higher than the ScSZ sample without co-doping. Consequently the activation energy of the co-doped sample was lower compared to the ScSZ sample.

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► Ytterbia co-doping in scandia stabilized zirconia suppressed formation of β phase.
► Ionic conductivity of the ytterbia co-doped sample was higher than 10ScSZ.
► Conductivity difference was higher at lower temperatures.
► Activation energy for conduction was lower in the co-doped sample than 10ScSZ.