High temperature properties of the n = 2 Ruddlesden–Popper phases (La,Sr)3(Fe,Ni)2O7−δ |
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| Affiliation: | 1. Key Laboratory of Physics and Technology for Advanced Batteries, Ministry of Education, College of Physics, Jilin University, Changchun 130012, PR, China;2. Beihua University, Jilin 132013, PR, China;1. International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan;2. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;3. Paul Scherrer Institut, Department of General Energy Research, CH-5225 Villigen, Switzerland |
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| Abstract: | The crystal chemistry and mixed conductor properties of the n = 2 member of the Ruddlesden–Popper (R–P) phases Sr3−xLaxFe2−yNiyO7−δ with 0 ≤ x ≤ 0.3 and 0 ≤ y ≤ 1.0 have been studied at high temperature. High-temperature X-ray diffraction and thermogravimetric measurements of the equilibrium pO2 (10− 5 ≤ pO2 ≤ 1 atm) in the temperature range 400 ≤ T ≤ 1000 °C indicate that the Sr3FeNiO7−δ phase is able to accommodate a large oxygen non-stoichiometry (δ ∼ 1.5) without structural transformations. The electrical conductivity and oxygen permeability increase with the substitution of Ni for Fe in the range 550 ≤ T ≤ 1000 °C. The electrical transport of the Sr3FeNiO7−δ phase is thermally activated and the activation energy decreases with the substitution of Ni for Fe for a given oxygen content. The increase in the oxygen permeation flux with increasing Ni content is due to an increasing oxygen non-stoichiometry and a lower activation energy for permeation. |
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