Phase formation and ionic conductivity studies on ytterbia co-doped scandia stabilized zirconia (0.9ZrO_2-0.09Sc_2O_3-0.01Yb_2O_3) electrolyte for SOFCs

摘要

The effect of ytterbia co-doping in scandia stabilized zirconia (ScSZ) on phase formation and electrical conductivity was studied. The ternary (ZrO_2)_(0.90)(Sc_2O_3)_(0.09)(Yb_2O_3)_(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.