Synthesizing of (Bi2O3)(1-x-y)(Ho2O3)(x)( Dy2O3)(y) Electrolytes for Intermediate-Temperature Solid Oxide Fuel Cells

Abstract

In present study, Ho2O3 and Dy2O3 doped Bi2O3 composite materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) were investigated. (Bi2O3)(1-x-y)(Ho2O3)(x)(Dy2O3)(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) delta-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 8.4 4 x 10(-2)-4.60 x 10(-1) S cm(-1) and their conductivity values corresponding to the intermediate-temperature region vary in the range 1.65 x 10(-3)-2.30 x 10(-1) S cm(-1). The activation energy values of the samples were calculated from log sigma 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.