Characterization of interconnects and cathodes for intermediate temperature solid oxide fuel cells

Abstract

Solid oxide fuel cells (SOFCs) have an electrolyte that is a solid, non-porous metal oxide, usually Y2O3-stablilized ZrO2. The cell operates at 600-1000 oC where ionic conduction by oxygen ions takes place. Typically, the anode is a Ni-ZrO2 cermet and the cathode is Sr-doped LaMnO3. There is no liquid electrolyte with its attendant material corrosion or electrolyte management problems. The high temperature of the SOFC, however, places stringent requirements on its materials. The development of suitable low cost materials and the low-cost fabrication of ceramic structures are presently the key technical challenges facing SOFCs. The objective of this dissertation is to characterize interconnect and cathode materials for SOFCs. In chapter III, LCC/glass composite interconnect materials for high temperature SOFCs were studied to improve the sintering ability and electrical conductivity of La0.8Ca0.2CrO3 (LCC). Glass is known as a sintering aid for improving sintering ability. It promotes liquid phase sintering and improves densification during the sintering process. The components of the glass used in this study are B2O3, SrO, La2O3, SiO2 and Al2O3.The phase stability, microstructure, electrical conductivity and thermal expansion coefficient (TEC) were measured to determine the optimal glass content in the composite materials. All of the tested composite materials showed perovskite structures and dense microstructures. It was found that the addition of up to 5 wt.% glass increased the sintering ability and the electrical conductivity in both air and hydrogen atmospheres. The glass powder enhances the sintering behavior because it acts as a liquid phase sintering aid and the Sr2+ ion in glass powder generates and . These lead to improvement in the electrical conductivity of the material. The TEC of the composites indicated compatibility with other cell components. The above results present that LCC/glass composite materials are suitable to be used as interconne...