The phase stability and conductivity of Ho2O3-Gd2O3 co-doped electrolyte for solid oxide fuel cell

In this study, Bi2O3 ternary system sample materials were synthesized by using solid state reaction method. Two oxides, Ho2O3 and Gd2O3, were used to stabilize the delta (cubic) Bi2O3 phase used as an electrolyte of solid oxide fuel cell applications. The characteristics and electrical properties of these electrolyte samples for solid oxide fuel cells were evaluated by X-ray diffraction (XRD), scanning electron microscope and the four-point probe technique. According to XRD measurements, delta-phase (x = 0.05-0.1, y = 0.05, 0.1, 0.15, 0.2) samples were obtained with a stable structure. The results of the electrical measurements of the (Bi2O3)(1-x-y)(Ho2O3)(x) (Gd2O3) y ternary system show that the electrical conductivity increase with decreasing amount of Gd2O3 molar ratio at a fixed molar ratio of Ho2O3. The value of highest conductivity was found as 2.53 x 10(-1) S cm(-1) for the (Bi2O3)(1-x-y)(Ho2O3)(x)(Gd2O32O3)(y) ternary system (x = 0.05 mol% and y = 0.05 mol%) at 973 K. It was found that activation energy at low temperature varied from 1.10 to 1.29 eV and the activation energy at high temperature varied from 0.61 to 0.70 eV.