Title:
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Tuning the high-temperature properties of Pr2NiO4+δ by simultaneous Pr- and Ni-cation replacement
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Author:
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Istomin, S. Ya.; Karakulina, O. M.; Rozova, M.G.; Kazakov, S.M.; Gippius, A.A.; Antipov, E.V.; Bobrikov, I.A.; Balagurov, A.M.; Tsirlin, A.A.; Michau, A.; Biendicho, J.J.; Svensson, G.
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Other authors:
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Institut de Recerca en Energía de Catalunya |
Abstract:
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Novel Pr2-xSrxNi1-xCoxO4±δ (x = 0.25; 0.5; 0.75) oxides with the tetragonal K2NiF4-type structure have been prepared. Room-temperature neutron powder diffraction (NPD) study of x = 0.25 and 0.75 phases together with iodometric titration results have shown the formation of hyperstoichiometric oxide for x = 0.25 (δ = 0.09(2)) and a stoichiometric one for x = 0.75. High-temperature X-ray powder diffraction (HT XRPD) showed substantial anisotropy of the thermal expansion coefficient (TEC) along the a- and c-axis of the crystal structure, which increases with increasing the Co content from TEC(c)/TEC(a) = 2.4 (x = 0.25) to 4.3 (x = 0.75). High-temperature NPD (HT NPD) study of the x = 0.75 sample reveals that a very high expansion of the axial (Ni/Co)-O bonds (75.7 ppm K-1 in comparison with 9.1 ppm K-1 for equatorial ones) is responsible for such behaviour, and is caused by a temperature-induced transition between low- and high-spin states of Co3+. This scenario has been confirmed by high-temperature magnetization measurements on a series of Pr2-xSrxNi1-xCoxO4±δ samples. For compositions with high Ni content (x = 0.25 and 0.5) we synthesised K2NiF4-type oxides Pr2-x-ySrx+y(Ni1-xCox)O4±δ, y = 0.0-0.75 (x = 0.25); y = 0.0-0.5 (x = 0.5). The studies of the TEC, high-temperature electrical conductivity in air, chemical stability of the prepared compounds in oxygen and toward interaction with Ce2-xGdxO2-x/2 (GDC) at high temperatures reveal optimal behaviour of Pr1.35Sr0.65Ni0.75Co0.25O4+δ. This compound shows stability in oxygen at 900°C and does not react with GDC at least up to 1200°C. It features low TEC of 13 ppm K-1 and high-temperature electrical conductivity in air of 280 S cm-1 at 900°C, thus representing a promising composition for use as a cathode material in intermediate temperature solid oxide fuel cells (IT-SOFC). © The Royal Society of Chemistry 2016. |
Subject(s):
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-Àrees temàtiques de la UPC::Enginyeria dels materials::Assaig de materials -Cathodes -Cerium -Chemical compounds -Chemical stability -Cobalt -Cobalt compounds -Crystal structure -Diffraction -Electric conductivity -Fuel cells -Gadolinium -Nickel -Praseodymium -Product development -Solid oxide fuel cells (SOFC) -Thermal expansion -X ray powder diffraction |
Rights:
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Attribution-NonCommercial-NoDerivs 3.0 Spain
http://creativecommons.org/licenses/by-nc-nd/3.0/es/ |
Document type:
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Article - Published version Article |
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