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Research Papers

Electrical Properties of Sr0.86 Y0.08 TiO3 Under Redox and Full Cell Fabrication Conditions

[+] Author and Article Information
Li Zhao

jb@apep.uci.edu Advanced Power and Energy Program, University of California, Irvine, CA 92697-3550

Jacob Brouwer1

jb@apep.uci.edu Advanced Power and Energy Program, University of California, Irvine, CA 92697-3550

1

Corresponding author.

J. Fuel Cell Sci. Technol 9(5), 051006 (Aug 22, 2012) (5 pages) doi:10.1115/1.4007117 History: Received May 10, 2012; Revised May 21, 2012; Published August 22, 2012; Online August 22, 2012

The effects of manufacturing and preparation conditions on the structural and electrical properties of Sr0.86 Y0.08 TiO3 (SYT) reduced in 5% NH3 (95% N2 ) are discussed. The realization of an SYT-based SOFC anode is challenging because the conductivity of SYT is highly dependent upon the thermal history combined with heat treatment atmosphere used in manufacturing. To obtain highly conductive SYT as a candidate for an SOFC anode material, all samples in this study were prereduced to 1400 °C under reducing conditions (ammonia) for 8 h. After prereduction, three samples were oxidized in air at 850 °C, 950 °C, and 1050 °C, respectively, for 4 h to evaluate the impact of oxidizing conditions in practical cell fabrication processes on the SYT conductivity. XRD analyses showed that the lattice parameter of SYT sintered in ammonia was slightly different than the sample sintered in air. Measured at 800 °C in reducing atmosphere (dry N2 /4% H2 ), the maximum electrical conductivity of 36.3 S/cm was observed in SYT reduced in ammonia at 1400 °C. However, the observed conductivities were not preserved after oxidation-reduction cycles. Various SYT samples prereduced in ammonia at 1400 °C and then oxidized in air at 850 °C, 950 °C, and 1050 °C showed an irreversible drop on conductivity measured in a reducing atmosphere, and the higher the oxidation temperature, the lower the conductivity became. The conductivity results indicate a strong dependence upon the SYT manufacturing and processing conditions. Despite the irreversible drop due to the oxidation cycle, the conductivity of SYT sintered in ammonia at 1400 °C is still reasonable as a candidate for SOFC anodes, with careful management of cell fabrication conditions to avoid any oxidation processes at temperatures above 1050 °C.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

SYT synthesis via modified Pechini method, (a) flow chart, (b) SYT SOL, (c) SYT gel, (d) SYT powder

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Figure 2

XRD patterns for samples prepared in different conditions

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Figure 3

Temperature dependence of the electrical conductivity measured in dry N2 /4% H2 for samples with different preparation conditions. All samples prereduced in dry N2 /4% H2 at 800 °C for 36 h.

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Figure 4

Time dependence of the electrical conductivity measured in dry N2 /4% H2 for samples with different preparation conditions, measured at 800 °C

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Figure 5

(a) Calculated ASR of 1 mm thick composite anode with various thermal histories, (b) microstructure of STY-YSZ composite after sintered to 1400 °C

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Figure 6

ASR of porous SYT-YSZ composite anode that is reduced at 1400 °C without any oxidative manufacturing processes in air, calculated and measured

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