Electrical and sintering behaviour of Y 2Zr 2O 7 (YZ) pyrochlore-based materials—the influence of bismuth

Abstract

Solid oxide fuel cell can convert fuels rich in H 2 into electrical energy directly without pollution by electrochemical reaction with oxygen. The efficiency of energy conversion and durability of performance mainly depend on the oxide ion conducting solid electrolyte activity. The global experience gained all these years in the solid oxide fuel cell (SOFC) development has prompted for a change from the state of the art functional electrolyte material, yttria-stabilized zirconia (YSZ), having a conductivity of 0.1 S cm −1 at 1000 °C, to a new material which exhibits equivalent conductivity values in the intermediate temperature range (600–700 °C). In this work, yttrium zirconate (Y 2Zr 2O 7 (YZ)), an ionic conducting stable pyrochlore-based oxide prepared by glycine nitrate combustion route, is systematically characterised. Both circular and rectangular pellets were fabricated by uniaxial compression followed by annealing at different temperatures. The functional properties such as porosity, percentage thermal shrinkage in volume and percentage densification of the sintered pellets are compiled. Bismuth oxide is found to be an effective sintering aid in general. So, the effect of bismuth oxide addition on YZ was investigated through sintering studies, X-ray diffraction (XRD), TGA/DTA, scanning electron microscopy (SEM) and conductivity measurements. The results obtained on YZ with and without bismuth oxide addition are discussed with respect to the requirement of an electrolyte for intermediate temperature solid oxide fuel cell (ITSOFC) application.