Swedenborgite-type oxides YBaCo4-xZnxO7+δ (x = 0.8, 1) as cathode materials for IT-SOFCs

Dmitry Tsvetkov, Ural Federal University, Ekaterinburg, Russian Federation
Nadezhda Tsvetkova, Ural Federal University, Ekaterinburg, Russian Federation
Andrey Zuev, Ural Federal University, Ekaterinburg, Russian Federation

The YBaCo4O7+δ oxide is considered as promising cathode material for intermediate temperature SOFCs due to lower thermal expansion coefficient (TEC) as compared to other cobalt-containing complex oxides [1]. The main disadvantage of YBaCo4O7+δ is its instability in the temperature range of 700–900 °C due to oxidation in the oxygen-containing atmosphere [2]. However, the substitution of Zn for Co is believed to enhance the stability of YBaCo4O7+δ [3]. The present work is devoted to study of YBaCo4-xZnxO7+δ (x = 0.8, 1) oxides as cathode materials for IT-SOFCs based on Ce0.8Sm0.2O1.9 solid electrolyte.

The YBaCo4-xZnxO7+δ (x = 0.8, 1) and Ce0.8Sm0.2O1.9 powders were prepared by glycerin-nitrate method. The products obtained were characterized by X-Ray diffraction using Shimadzu XRD-7000 diffractometer (Cu Kα radiation). The chemical reactivity tests were carried out by mixing the YBaCo4-xZnxO7+δ (x = 0.8, 1) and the Ce0.8Sm0.2O1.9 powders with subsequent calcination at different temperatures. Thermal expansion coefficients of the samples were evaluated using dilatometer NETZSCH DIL 402 C in the temperature range 30–1100 °C in air. Electrical conductivity of the samples was measured with a four-probe direct current method in the temperature range 30–1100 °C in air. Polarization measurements were carried out by electrochemical impedance spectroscopy with an “Elins Z500-PX” impedance analyzer in the frequency range 10 Hz–0.5 MHz and temperature range 600–750 °C with 25 °C steps.

Acknowledgement: This work was supported by the project SP-3440.2016.1 funded by the President of the Russian Federation.

[1] E.V. Tsipis, V.V. Kharton, J.R. Frade, P. Núnez, J. Solid State Electrochem, Vol. 9 (2005), p. 547–557.
[2] M. Karppinen, H. Yamauchi, S. Otani, T. Fujita, T. Motohashi, Y.-H. Huang, M. Valkeapää, H. Fjellvåg, Chem. Mater, Vol. 18 (2006), p. 490–494.
[3] D.S. Tsvetkov, N.S. Tsvetkova, I.L. Ivanov, A.Yu. Zuev, Solid State Ionics, Vol. 309 (2017), p. 92–99.

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