High-temperature redox chemistry of La1.5+xSr0.5-xCo0.5Ni0.5O4+delta (x=0.0, 0.2) studied in situ by neutron diffraction
Neutron powder diffraction has been used to investigate the redox behaviour of two n = 1 Ruddlesden-Popper (RP) oxides, La1.5+xSr 0.5-xCo0.5Ni0.5O4+δ (x = 0.0, 0.2) in situ and in real time during cycling through the temperature range 20 < T/°C < 600 under flowing 5% H2. Both compositi...
| Main Authors: | , , , , , , |
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| Format: | Journal article |
| Language: | English |
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2011
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| _version_ | 1826264609079689216 |
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| author | Tonus, F Greaves, C El Shinawi, H Hansen, T Hernandez, O Battle, P Bahout, M |
| author_facet | Tonus, F Greaves, C El Shinawi, H Hansen, T Hernandez, O Battle, P Bahout, M |
| author_sort | Tonus, F |
| collection | OXFORD |
| description | Neutron powder diffraction has been used to investigate the redox behaviour of two n = 1 Ruddlesden-Popper (RP) oxides, La1.5+xSr 0.5-xCo0.5Ni0.5O4+δ (x = 0.0, 0.2) in situ and in real time during cycling through the temperature range 20 < T/°C < 600 under flowing 5% H2. Both compositions retained I4/mmm symmetry throughout the heating and cooling cycle. Rietveld refinement of data collected at room temperature showed the presence of interstitial oxygen in the original samples (δ ≈ 0.06(1) and 0.12(1) for x = 0.0 and 0.2, respectively). When heated in flowing H2, both compositions were reduced over the temperature range 300 < T/°C < 600 (δ ≈ -0.22(2) and -0.06(2) for x = 0.0 and 0.2, respectively). In the case of the x = 0.2 material, reduction clearly occurred first at the interstitial site (Oint), then at the equatorial site (O eq). The changes in composition were accompanied by changes in unit-cell parameters and bond lengths. Rietveld refinements revealed residual partial occupation of the Oint site in the reduced x = 0.2 sample. This is the first structural evidence of the coexistence of both anion vacancies and interstitial anions in a hypostoichiometric n = 1 RP oxide. The temperature dependence of the atomic displacement parameters is consistent with the presence of local rotations of the anion-deficient coordination polyhedra. On heating the reduced x = 0.2 material in an O2 flow, the refilling of both the Oeq and Oint sites began at 200 °C and the stoichiometry of the original as-prepared sample was recovered by 250 °C. © 2011 The Royal Society of Chemistry. |
| first_indexed | 2024-03-06T20:10:35Z |
| format | Journal article |
| id | oxford-uuid:2a6dfb95-86a5-491b-b343-6ff12791e54c |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T20:10:35Z |
| publishDate | 2011 |
| record_format | dspace |
| spelling | oxford-uuid:2a6dfb95-86a5-491b-b343-6ff12791e54c2022-03-26T12:24:56ZHigh-temperature redox chemistry of La1.5+xSr0.5-xCo0.5Ni0.5O4+delta (x=0.0, 0.2) studied in situ by neutron diffractionJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:2a6dfb95-86a5-491b-b343-6ff12791e54cEnglishSymplectic Elements at Oxford2011Tonus, FGreaves, CEl Shinawi, HHansen, THernandez, OBattle, PBahout, MNeutron powder diffraction has been used to investigate the redox behaviour of two n = 1 Ruddlesden-Popper (RP) oxides, La1.5+xSr 0.5-xCo0.5Ni0.5O4+δ (x = 0.0, 0.2) in situ and in real time during cycling through the temperature range 20 < T/°C < 600 under flowing 5% H2. Both compositions retained I4/mmm symmetry throughout the heating and cooling cycle. Rietveld refinement of data collected at room temperature showed the presence of interstitial oxygen in the original samples (δ ≈ 0.06(1) and 0.12(1) for x = 0.0 and 0.2, respectively). When heated in flowing H2, both compositions were reduced over the temperature range 300 < T/°C < 600 (δ ≈ -0.22(2) and -0.06(2) for x = 0.0 and 0.2, respectively). In the case of the x = 0.2 material, reduction clearly occurred first at the interstitial site (Oint), then at the equatorial site (O eq). The changes in composition were accompanied by changes in unit-cell parameters and bond lengths. Rietveld refinements revealed residual partial occupation of the Oint site in the reduced x = 0.2 sample. This is the first structural evidence of the coexistence of both anion vacancies and interstitial anions in a hypostoichiometric n = 1 RP oxide. The temperature dependence of the atomic displacement parameters is consistent with the presence of local rotations of the anion-deficient coordination polyhedra. On heating the reduced x = 0.2 material in an O2 flow, the refilling of both the Oeq and Oint sites began at 200 °C and the stoichiometry of the original as-prepared sample was recovered by 250 °C. © 2011 The Royal Society of Chemistry. |
| spellingShingle | Tonus, F Greaves, C El Shinawi, H Hansen, T Hernandez, O Battle, P Bahout, M High-temperature redox chemistry of La1.5+xSr0.5-xCo0.5Ni0.5O4+delta (x=0.0, 0.2) studied in situ by neutron diffraction |
| title | High-temperature redox chemistry of La1.5+xSr0.5-xCo0.5Ni0.5O4+delta (x=0.0, 0.2) studied in situ by neutron diffraction |
| title_full | High-temperature redox chemistry of La1.5+xSr0.5-xCo0.5Ni0.5O4+delta (x=0.0, 0.2) studied in situ by neutron diffraction |
| title_fullStr | High-temperature redox chemistry of La1.5+xSr0.5-xCo0.5Ni0.5O4+delta (x=0.0, 0.2) studied in situ by neutron diffraction |
| title_full_unstemmed | High-temperature redox chemistry of La1.5+xSr0.5-xCo0.5Ni0.5O4+delta (x=0.0, 0.2) studied in situ by neutron diffraction |
| title_short | High-temperature redox chemistry of La1.5+xSr0.5-xCo0.5Ni0.5O4+delta (x=0.0, 0.2) studied in situ by neutron diffraction |
| title_sort | high temperature redox chemistry of la1 5 xsr0 5 xco0 5ni0 5o4 delta x 0 0 0 2 studied in situ by neutron diffraction |
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