Redox Behaviour of Potential SOFC Cathode Materials La1.6Sr0.4Ni1-xCoxO4+δ (x = 0.6 and 0.8) Determined from In Situ Neutron Powder Diffraction under Flowing O2 and 5%H2
| Autor: | Thibault Broux, Carmelo Prestipino, Florent Tonus, Mona Bahout, James M. Hanlon |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
010302 applied physics
Materials science Hydrogen Thermodynamic equilibrium Mechanical Engineering Analytical chemistry chemistry.chemical_element 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Decomposition Oxygen Redox Isothermal process chemistry Mechanics of Materials Impurity 0103 physical sciences General Materials Science 0210 nano-technology Thermal analysis |
| Zdroj: | Key Engineering Materials. 617:89-93 |
| ISSN: | 1662-9795 |
| DOI: | 10.4028/www.scientific.net/kem.617.89 |
| Popis: | The n = 1 Ruddlesden-Popper (RP) oxides La1.6Sr0.4Ni1-xCoxO4+δ (x = 0.6 and 0.8) have been prepared by the citrate-gel method and studied using thermal analysis and in situ neutron powder diffraction (NPD) under oxygen (x = 0.6) and subsequent 5%H2 flow. On heating under O2, the x = 0.6 sample loses oxygen from the interstitial site until it is emptied at 475 °C. Subsequent heating in 5%H2 results in reduction which proceeds within two-steps; the first one occurs between ~170 and 300 °C and involves removal of the interstitial oxygen (Oint), the second step starting at ~ 400 °C and going on up to 600 °C (the highest temperature reached) involves oxygen deintercalation from the equatorial position (Oeq). After 20 min of isothermal heating at 600 °C, unless a thermodynamic equilibrium state was not reached there was no sign of impurity related to the decomposition of the sample and the composition refined to La1.6Sr0.4Ni0.4Co0.6O3.85(3). The x = 0.8 sample exhibits similar behavior under hydrogenwith slight shifts in temperature and the composition reached after the reducing cycle refined to La1.6Sr0.4Ni0.2Co0.8O3.85(1). This study demonstrates that the Co-rich La1.6Sr0.4Ni1-xCoxO4+δ oxides can withstand hydrogen reducing conditions with topotactic deintercalation of Oint and Oeq but are not stable enough at 600 °C in comparison to La1.5Sr0.5Ni0.5Co0.5O4+δ owing toincreased Sr/La ratio in the latter. |
| Databáze: | OpenAIRE |
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