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Research Papers

Sintering Characteristics and Electrical Conductivity of (Sr1−x Lax )TiO3 Synthesized by the Citric Acid Method

[+] Author and Article Information
Zhenwei Wang

 Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka, Kanagawa 240-0196, Japan

Masashi Mori1

 Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka, Kanagawa 240-0196, Japanmasashi@criepi.denken.or.jp

1

Corresponding author.

J. Fuel Cell Sci. Technol 8(5), 051018 (Jul 05, 2011) (5 pages) doi:10.1115/1.4003993 History: Received January 25, 2011; Revised April 05, 2011; Published July 05, 2011; Online July 05, 2011

The air-sintering characteristics and electrical conductivity of (Sr1−x Lax )TiO3 perovskites (0 ≤ x ≤ 0.3) synthesized by the citric acid method were evaluated in terms of their use as interconnect materials in solid oxide fuel cells. A single perovskite phase of (Sr0.8 La0.2 )TiO3 powder was formed at 800 °C. In this powder, a Ruddlesden–Popper Sr2 TiO4 layer appeared in the temperature range of 1100–1500 °C, and disappeared at 1600 °C. (Sr0.8 La0.2 )TiO3 powders which were calcined at 1000–1100 °C showed the best sintering characteristics. The relative density of the samples reached 94% at 1400 °C, although the Ruddlesden–Popper layer remained in this dense sample. Electrical conductivities of (Sr1−x Lax )TiO3 bars at 1000 °C were approximately 0.10–1.1 S cm−1 in air and 7.1–12 S cm−1 in a reducing atmosphere. For a (Sr0.9 La0.1 )TiO3 pellet placed between both air and reducing atmospheres, the conductivity at 850 °C was 0.033 S cm−1 , which is close to that in air. No compositional dependency on electrical conductivity was observed for the (Sr1−x Lax )TiO3 pellets.

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Figures

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Figure 1

Experimental equipment for electrical conductivity measurement of the (Sr1 − x Lax )TiO3 pellet placed in an SOFC atmosphere condition

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Figure 2

XRD patterns of (Sr0.8 La0.2 )TiO3 after firing at selected temperatures for 5 h. (a) Firing at 800-1100 °C. (b) Firing at 1200–1600 °C. The symbols (×) represent the second phase (Sr2 TiO4 ).

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Figure 3

Lattice parameters of (Sr0.8 La0.2 )TiO3 as a function of firing temperature

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Figure 4

Relative density of (Sr0.8 La0.2 )TiO3 as a function of firing temperature

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Figure 5

SEM micrographs of (Sr0.8 La0.2 )TiO3 after firing at 1600 °C. (a) Surface-section. (b) Cross-section.

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Figure 6

SEM micrographs of (Sr0.7 La0.3 )TiO3 after firing at 1600 °C. (a) Surface-section. (b) Cross-section.

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Figure 7

SEM micrographs of (Sr0.9 La0.1 )TiO3 after firing at 1650 °C. (a) Surface-section. (b) Cross-section.

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Figure 8

Temperature dependency of electrical conductivity of the (Sr1 − x Lax )TiO3 bar samples. (a) In air. (b) In 30% H2 -N2 atmosphere.

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Figure 9

Electrical conductivity of the (Sr1 − x Lax )TiO3 bar samples as a function of La content. (a) In air. (b) In 30% H2 -N2 atmosphere.

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Figure 10

Electrical conductivity of the dense (Sr0.9 La0.1 )TiO3 pellet sample. (a) Time dependence of the conductivity at 850 °C after supplying 30% H2 –N2 gas. (b) Temperature dependence of the conductivity in an SOFC atmosphere.

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Figure 11

Temperature dependence of electrical conductivity of the dense (Sr1 − x Lax )TiO3 pellet samples in an SOFC atmosphere condition

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