Conductivity Degradation of Transition Metal (Mn, Fe, Co) Doped Yttria Stabilized Zirconia by Phase Transformation

Abstract

Conductivity degradation behavior of 1 mol% transition metal (Mn, Fe, Co) doped yttria stabilized zirconia (YSZ) under SOFC operation atmospheres was examined by AC impedance technique under an OCV condition, using a test cell consisting of dry air, Pt / transition metal (Mn, Fe, Co) doped 8YSZ / Pt, 1.2 % H2O–H2, at 1173 K for 300 h. Phase transformation of YSZ from the cubic to the tetragonal phase was analyzed by Raman spectroscopy. The phase transformation occurs significantly in the area corresponding to the transition metal oxides reduction in the YSZ lattice. Cross section analysis of the tested electrolyte revealed that color changed into dark from the anode side surface to inside the electrolyte. Micro-Raman analysis indicated the phase transformation of transition metal (Mn, Fe, Co) doped 8YSZ from the cubic phase to the tetragonal phase. We have experimentally demonstrated that the conductivity degradation of transition metal (Mn, Fe, Co) doped YSZ is closely associated to the phase transformation under SOFC operation atmospheres at 1173 K. All the transition metal (Mn, Fe, Co) doped YSZ showed a lesser conductivity degradation and a lower phase transformation than the Ni doped YSZ. The Fe doped YSZ showed the least Conductivity degradation and lowest phase transformation during the transition metal (Mn, Fe, Co, Ni) doped YSZ under SOFC operation atmospheres at 1173K.