1
|
Poienar M, Gutmann MJ, Pascut GL, Petříček V, Stenning G, Vlazan P, Sfirloaga P, Paulmann C, Tolkiehn M, Manuel P, Veber P. Phase Transitions and Physical Properties of the Mixed Valence Iron Phosphate Fe 3(PO 3OH) 4(H 2O) 4. MATERIALS (BASEL, SWITZERLAND) 2022; 15:8059. [PMID: 36431543 PMCID: PMC9696478 DOI: 10.3390/ma15228059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 11/03/2022] [Accepted: 11/10/2022] [Indexed: 06/16/2023]
Abstract
Iron phosphate materials have attracted a lot of attention due to their potential as cathode materials for lithium-ion rechargeable batteries. It has been shown that lithium insertion or extraction depends on the Fe mixed valence and reduction or oxidation of the Fe ions' valences. In this paper, we report a new synthesis method for the Fe3(PO3OH)4(H2O)4 mixed valence iron phosphate. In addition, we perform temperature-dependent measurements of structural and physical properties in order to obtain an understanding of electronic-structural interplay in this compound. Scanning electron microscope images show needle-like single crystals of 50 μm to 200 μm length which are stable up to approximately 200 °C, as revealed by thermogravimetric analysis. The crystal structure of Fe3(PO3OH)4(H2O)4 single crystals has been determined in the temperature range of 90 K to 470 K. A monoclinic isostructural phase transition was found at ~213 K, with unit cell volume doubling in the low temperature phase. While the local environment of the Fe2+ ions does not change significantly across the structural phase transition, small antiphase rotations occur for the Fe3+ octahedra, implying some kind of electronic order. These results are corroborated by first principle calculations within density functional theory, which also point to ordering of the electronic degrees of freedom across the transition. The structural phase transition is confirmed by specific heat measurements. Moreover, hints of 3D antiferromagnetic ordering appear below ~11 K in the magnetic susceptibility measurements. Room temperature visible light absorption is consistent with the Fe2+/Fe3+ mixed valence.
Collapse
Affiliation(s)
- Maria Poienar
- National Institute for Research and Development in Electrochemistry and Condensed Matter, Str. Dr. Aurel Păunescu Podeanu Nr. 144, 300569 Timisoara, Romania
- MANSiD Research Center and Faculty of Forestry, Stefan Cel Mare University, 720229 Suceava, Romania
| | | | - Gheorghe Lucian Pascut
- MANSiD Research Center and Faculty of Forestry, Stefan Cel Mare University, 720229 Suceava, Romania
| | - Václav Petříček
- Institute of Physics, Academy of Sciences of the Czech Republic, 182 21 Prague 8, Czech Republic
| | - Gavin Stenning
- Rutherford Appleton Laboratory, ISIS Facility, Chilton Didcot, Oxfordshire OX11 0QX, UK
| | - Paulina Vlazan
- National Institute for Research and Development in Electrochemistry and Condensed Matter, Str. Dr. Aurel Păunescu Podeanu Nr. 144, 300569 Timisoara, Romania
| | - Paula Sfirloaga
- National Institute for Research and Development in Electrochemistry and Condensed Matter, Str. Dr. Aurel Păunescu Podeanu Nr. 144, 300569 Timisoara, Romania
| | - Carsten Paulmann
- Mineralogisch-Petrographisches Institute, Universität Hamburg, 20146 Hamburg, Germany
| | - Martin Tolkiehn
- Deutsches Elektronensynchrotron DESY, Notkestrasse 85, 22603 Hamburg, Germany
| | - Pascal Manuel
- Rutherford Appleton Laboratory, ISIS Facility, Chilton Didcot, Oxfordshire OX11 0QX, UK
| | - Philippe Veber
- Institut Lumière Matière, Université Claude Bernard Lyon 1, University of Lyon, CNRS, F-69622 Villeurbanne, France
| |
Collapse
|