Na2Fe0.9Mn0.1PO4F Composite as Cathode Material: Structural, Magnetic, and Mössbauer Studies

• Published in: IEEE transactions on magnetics 2021-02, Vol.57 (2), p.1-4
• Main Authors: Seo, Jae Yeon, Choi, Hyunkyung, Lee, Ah-Yeon, Park, Seung-Young, Kim, Chul Sung
• Format: Article
• Language: English
• Subjects: Ball milling; Batteries; Cathodes; Crystal structure; Crystals; Electrode materials; Fluorine; Ions; Iron; Magnetic properties; Magnetism; Manganese; Mossbauer spectroscopy; Mössbauer spectroscopy; Octahedrons; Quadrupoles; sodium–iron–fluorophosphate; Spectrum analysis; Superconducting quantum interference devices; superexchange interaction; Temperature dependence; Temperature measurement; X-ray diffraction
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2020.3014738

Mn-doped sodium iron fluorophosphates Na 2 Fe 0.9 Mn 0.1 PO 4 F were synthesized using ball milling via a solid-state reaction route. The crystal structure and magnetic properties of the as-prepared materials were studied by using X-ray diffraction (XRD), superconducting quantum interference device (SQUID), and Mössbauer spectroscopy. Structural refinement of Na 2 Fe 0.9 Mn 0.1 PO 4 F was analyzed using the Fullprof program. From the XRD patterns, the crystal structure was found to be orthorhombic with the space group Pbcn . Na 2 Fe 0.9 Mn 0.1 PO 4 F has a 2-D layered structure composed of a pair of Fe(Mn)O 4 F 2 octahedrons through fluorine ion sharing, similar to that of Na 2 FePO 4 F. The temperature dependence of the zero-field-cooled (ZFC) and field-cooled (FC) curves was measured at temperatures ranging from 1.8 to 295 K under an applied field of 100 Oe. We confirmed that the Néel temperature was 2.5 K, which is lower than that of Na 2 FePO 4 F ( T_{N} =3.4 K). Mössbauer spectroscopy measurements at 4.2-295 K were conducted. At all the temperatures, the spectra were fitted with a double and were determined to be Fe 2+ ions based on an isomer shift ( \delta ). In addition, the large value of the electric quadrupole splitting ( \Delta E_{Q} ) is explained by the asymmetric local environment of the Fe ions.