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King G. New examples of non-cooperative octahedral tilting in a double perovskite: phase transitions in K 3GaF 6. ACTA CRYSTALLOGRAPHICA SECTION B, STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS 2020; 76:789-794. [PMID: 33017312 DOI: 10.1107/s2052520620009695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 07/16/2020] [Indexed: 06/11/2023]
Abstract
The crystal structures of three polymorphs of K3GaF6 and the transition temperatures between these phases are reported for the first time. Synchrotron powder diffraction data clearly show that at 300 K α-K3GaF6 crystallizes in space group I41/a with lattice parameters of a = 19.1124 (3) Å, c = 34.4165 (6) Å, and Z = 80. The structure is based on the double perovskite but with two fifths of the GaF6 octahedra rotated by ∼45°. This phase remains stable until ∼460 K, above which it undergoes a transition to I4/m with lattice parameters of a = 13.6088 (4) Å, c = 8.6764 (3) Å, and Z = 10 at 485 K. β-K3GaF6 has a similar structure but with only one fifth of the GaF6 rotated by ∼45°. Above ∼510 K, the cubic Fm3m δ-K3GaF6 structure is stabilized, with a lattice parameter of a = 8.6649 (1) Å at 550 K. The F atoms have highly anisotropic displacement parameters which suggest dynamic octahedral tilting is occurring. This work expands the fairly small group of double perovskite compounds which display non-cooperative patterns of octahedral tilting.
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Affiliation(s)
- Graham King
- Material and Chemical Sciences, Canadian Light Source, 44 Innovation Blvd, Saskatoon, SK S7N 2V3, Canada
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Gao Y, Nolan AM, Du P, Wu Y, Yang C, Chen Q, Mo Y, Bo SH. Classical and Emerging Characterization Techniques for Investigation of Ion Transport Mechanisms in Crystalline Fast Ionic Conductors. Chem Rev 2020; 120:5954-6008. [DOI: 10.1021/acs.chemrev.9b00747] [Citation(s) in RCA: 81] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yirong Gao
- University of Michigan−Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai CN-200240, China
| | - Adelaide M. Nolan
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Peng Du
- University of Michigan−Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai CN-200240, China
| | - Yifan Wu
- University of Michigan−Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai CN-200240, China
| | - Chao Yang
- University of Michigan−Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai CN-200240, China
| | - Qianli Chen
- University of Michigan−Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai CN-200240, China
| | - Yifei Mo
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States
- Maryland Energy Innovation Institute, University of Maryland, College Park, Maryland 20742, United States
| | - Shou-Hang Bo
- University of Michigan−Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai CN-200240, China
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King G, Avdeev M, Qasim I, Zhou Q, Kennedy BJ. Multi-scale structural analysis of the A-site and oxygen deficient perovskite Sr 11Mo 4O 23. Dalton Trans 2017; 46:12466-12473. [PMID: 28869268 DOI: 10.1039/c7dt02087b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The long range average crystal structure, as well as the short and medium range structural features, of the A-site deficient and oxygen deficient perovskite Sr11Mo4O23 have been determined. Rietveld refinement of synchrotron X-ray and neutron powder diffraction data show that this compound is cubic with space group Fd3[combining macron]m and a lattice parameter of a = 16.4108 Å. These findings contradict earlier reports of a tetragonal crystal structure. Sr11Mo4O23 appears to be isostructural with Ba11W4O23, except that the disordered coordination environment around one of the Mo sites seems to be a mixture of octahedral and square pyramidal instead of octahedral and tetrahedral. The short and medium range structural features have been inspected using the neutron pair distribution function (PDF). Short range correlations between the oxygen polyhedra surrounding the Mo(2) atom exist to avoid short O-O contacts. A model has been constructed which contains such correlations and is verified by reverse Monte Carlo (RMC) modeling of the PDF. The RMC refinements also give the distribution of inter-atomic distances in this compound which reveals how the various atomic positions are correlated and over what length scales. These results are important for understanding the ionic conduction pathways.
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Affiliation(s)
- Graham King
- Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
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King G, Thompson CM, Luo K, Greedan JE, Hayward MA. Identifying the local structural units in La 0.5Ba 0.5MnO 2.5 and BaY 0.25Fe 0.75O 2.5 through the neutron pair distribution function. Dalton Trans 2017; 46:1145-1152. [PMID: 28054073 DOI: 10.1039/c6dt04291k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Neutron pair distribution function data are used to investigate the local structures of two oxygen deficient perovskites with simple cubic crystal structures. La0.5Ba0.5MnO2.5 is found to have alternating layers of MnO6 octahedra and MnO4 tetrahedra, making it similar to other members of the La1-xBaxMnO2.5 series with smaller x values which have brownmillerite crystal structures. Our fitting results suggest that La0.5Ba0.5MnO2.5 is not locally similar to any one brownmillerite structure type but instead has a variety of intra-layer and inter-layer relationships. We propose that this could be due to short range segregation of the much differently sized La3+ and Ba2+ cations, which creates significantly different inter-layer distances. BaY0.25Fe0.75O2.5 is found not to have a brownmillerite-type local structure but rather seems to consist of structural units which are similar to Ba3YFe2O7.5, an earlier member of the BanYFen-1O2.5n series. The PDF analysis shows that there are never neighboring Y atoms and that the O vacancies lie exclusively between Fe atoms, such that Y is always octahedrally coordinated. The PDF also suggests that there are more tetrahedral Fe than expected, which could be due to the presence of terminal O atoms in Fe centered dimeric units, similar to what is found in Ba3YFe2O7.5.
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Affiliation(s)
- Graham King
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
| | - Corey M Thompson
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907, USA and Department of Chemistry and Brockhouse Institute of Materials Research, McMaster University, Hamilton, ON L8S 4M1, Canada
| | - Kun Luo
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK
| | - John E Greedan
- Department of Chemistry and Brockhouse Institute of Materials Research, McMaster University, Hamilton, ON L8S 4M1, Canada
| | - Michael A Hayward
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK
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de Laune BP, Rees GJ, Whitaker MJ, Hah HY, Johnson CE, Johnson JA, Brown DE, Tucker MG, Hansen TC, Berry FJ, Hanna JV, Greaves C. Oxygen Insertion Reactions within the One-Dimensional Channels of Phases Related to FeSb 2O 4. Inorg Chem 2017; 56:594-607. [PMID: 27977159 DOI: 10.1021/acs.inorgchem.6b02466] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structure of the mineral schafarzikite, FeSb2O4, has one-dimensional channels with walls comprising Sb3+ cations; the channels are separated by edge-linked FeO6 octahedra that form infinite chains parallel to the channels. Although this structure provides interest with respect to the magnetic and electrical properties associated with the chains and the possibility of chemistry that could occur within the channels, materials in this structural class have received very little attention. Here we show, for the first time, that heating selected phases in oxygen-rich atmospheres can result in relatively large oxygen uptakes (up to ∼2% by mass) at low temperatures (ca. 350 °C) while retaining the parent structure. Using a variety of structural and spectroscopic techniques, it is shown that oxygen is inserted into the channels to provide a structure with the potential to show high one-dimensional oxide ion conductivity. This is the first report of oxygen-excess phases derived from this structure. The oxygen insertion is accompanied not only by oxidation of Fe2+ to Fe3+ within the octahedral chains but also Sb3+ to Sb5+ in the channel walls. The formation of a defect cluster comprising one 5-coordinate Sb5+ ion (which is very rare in an oxide environment), two interstitial O2- ions, and two 4-coordinate Sb3+ ions is suggested and is consistent with all experimental observations. To the best of our knowledge, this is the first example of an oxidation process where the local energetics of the product dictate that simultaneous oxidation of two different cations must occur. This reaction, together with a wide range of cation substitutions that are possible on the transition metal sites, presents opportunities to explore the schafarzikite structure more extensively for a range of catalytic and electrocatalytic applications.
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Affiliation(s)
| | - Gregory J Rees
- Department of Physics, University of Warwick , Coventry CV4 7AL, U.K
| | | | | | | | | | - Dennis E Brown
- Department of Physics, Northern Illinois University , DeKalb, Illinois 60115, United States
| | - Matthew G Tucker
- Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | | | - Frank J Berry
- School of Chemistry, University of Birmingham , Birmingham B15 2TT, U.K
| | - John V Hanna
- Department of Physics, University of Warwick , Coventry CV4 7AL, U.K
| | - Colin Greaves
- School of Chemistry, University of Birmingham , Birmingham B15 2TT, U.K
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