Bismuth oxide doped scandia-stabilized zirconia electrolyte for the intermediate temperature solid oxide fuel cells

Abstract

Electrical and structural properties of bismuth oxide doped scandia-stabilized zirconia (ScSZ) electrolyte for solid oxide fuel cells (SOFCs) have been evaluated by means of XRD, TGA, DTA, and impedance spectroscopy. The amount of Bi 2O 3 in the ScSZ was varied in the range of 0.25–2.0 mol%. The original ScSZ samples indicated a rhombohedral crystalline structure that in general has lower conductivity than the cubic phase. However, the addition of Bi 2O 3 to ScSZ electrolyte was found to stabilize the cubic crystalline phase as detected by XRD. Impedance spectroscopy measurements in the temperature range between 350 and 900 °C indicated a sharp increase in conductivity for the system containing 2 mol% of Bi 2O 3 that is attributed to the presence of the cubic phase. In addition, impedance spectroscopy measurements revealed significant decrease of both the grain bulk and grain boundary resistances with respect to the temperature change from 600 to 900 °C and concentration of Bi 2O 3 from 0.5 to 2 mol%. The electrical conductivity at 600 °C obtained for 2 mol% Bi 2O 3 doped ScSZ was 0.18 S cm −1.