The Influence of Interface Structures on the Conducting Properties of Zirconia (ZrO2)-Based Solid Electrolytes

Abstract

Zirconia-based materials are the solid electrolytes used as the principal component of solid oxide fuel cells. The present generation of fuel cell designs incorporates self-supporting thin films (80–100 μm) of the electrolyte on which various coatings of electrode are applied. The operating temperature of the cell is currently in the range 800–1000°C, and understanding the interface structures associated with these structurally complex components at these temperatures remains a constant challenge. Incremental changes in conductivity brought on by interface modifications can have a large influence on the viability of any particular system for commercial application. This review outlines the influence that a number of interface structures associated specifically with zirconia-based electrolytes have on the ionic conductivity. These include grain boundary structures, structures within grains, and the influence of additives. In addition, the effect of long-term anneals on the various interfaces is addressed. In each case, the combination of ionic conductivity measurements with detailed analytical electron microscopy has provided the clues as to how the various interface structures influence the physical properties of the solid electrolyte ceramic.