Processing of LaCrO₃ Solid Oxide Fuel Cell Applications

Abstract

In this portion of the research the authors are focusing on the microstructure <-- --> property relations in solid oxide fuel cells (SOFC's) to better understand the mechanisms involved in cell performance. The overall aim is to fabricate SOFC's with controlled microstructures utilizing La{sub 1-x}Sr{sub x}MnO{sub 3} (LSM), yttria stabilized zirconia (YSZ), and Ni-YSZ composites as the cathode, electrolyte, and anode, respectively. Ideally, the electrode materials would be tailored for an increased reaction rate (grain size {le} 1 {micro}m), be stable with time (> 10,000 h), have a thermal expansion match to YSZ ({alpha} {approx} 11 x 10{sup -6}/C), show limited chemical interaction with the electrolyte, and show no degradation in electrical performance. This paper describes anodic studies, including starting powder characteristics, electrical conductivity and overpotential measurements, and resultant microstructures as a function of processing conditions (i.e. powder calcination temperature, and annealing temperature) and composition. During the last year several important discoveries have been made regarding the influence of composition and microstructure of anodes on the performance of the SOFCs. These results can be summarized as follows: (1) YSZ anodes prepared with lower Ni volume fractions (40 and 45%) resulted in lower overpotentials and improved stability. (2) Higher sintering temperatures effectively lowered the overpotential and increased the in-plane conductivity. Due to constrained sintering between the anode and the YSZ electrolyte, higher sintering temperatures allowed more densification in the z-direction, resulting in a rigid YSZ structure to support Ni particles. (3) By decreasing the densification between Ni grains, there are more paths for conduction (more Ni-Ni contacts throughout the structure and higher conductivities) and a larger number of Ni-YSZ contacts (lower overpotentials). (4) The 45 vol% Ni composition co-fired with the electrolyte had the lowest initial overpotential of any cermet with a similar composition.

Department(s)

Materials Science and Engineering

Sponsor(s)

United States. Department of Energy

Keywords and Phrases

30 Direct Energy Conversion; Annealing; Anodes; Calcination; Cermets; Electric Conductivity; Electrodes; Electrolytes; Microstructure; Oxides; Processing; Reaction Kinetics; Sintering; Solid Oxide Fuel Cells; Stability; Thermal Expansion

Document Type

Technical Report

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1999 University of Missouri--Rolla, All rights reserved.

Publication Date

01 Nov 1999

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