Synthesizing of (Bi₂O₃)_{1-x-y}(Ho₂O₃)_x(Dy₂O₃)_y Electrolytes for Intermediate-Temperature Solid Oxide Fuel Cells

In present study, Ho₂O₃ and Dy₂O₃ doped Bi₂O₃ composite materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) were investigated. $(Bi_2 O_3)_{1-x-y}(Ho_2 O_3)_x(Dy_2 O_3)_y$ ternary systems (x=0.11, 0.13, 0.15 and y=0.01, 0.03, 0.05, 0.07) were fabricated using conventional solid-state synthesis techniques. The samples were characterized by means of X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, differential thermal analysis/thermal gravimeter, and the four-point probe technique. X-ray powder diffraction measurements indicated that all samples have the stable fluorite type face centered cubic (fcc) δ-Bi₂O₃ phase. Scanning electron microscopy micrographs of all of the samples showed that grain size distribution was uniform. Four-point probe technique measurements showed that the conductivity of the samples increase with increase of temperature. Additionally, it has been found that the maximum conductivity values of all samples fall in a range $8.44×10^{-2}-4.60×10^{-1} Scm^{-1}$ and their conductivity values corresponding to the intermediate-temperature region vary in the range $1.65×10^{-3}-2.30×10^{-1} Scm^{-1}$. The activation energy values of the samples were calculated from łogσ graphics versus 1000/T using the Arrhenius equation. It was found that there is a good agreement between the activation energy values and conductivity values.