Structural and magnetic characterization of barbosalite Fe3(PO4)2(OH)2

Poienar, Maria; Damay, F.; Rouquette, Jérôme; Ranieri, V.; Malo, Sylvie; Maignan, A.; Elkaı̈m, Erik; Haines, J.; Martin, C.

doi:10.1016/j.jssc.2020.121357

Cited by 5 publications

(1 citation statement)

References 23 publications

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“…Among these routes, hydrothermal synthesis was the most successful in synthesizing the naturally occurring or unknown phases of iron hydroxyphosphates or hydrate phosphates. Although many studies have been dedicated to the structural, magnetic, electronic and catalytic properties of iron phosphate minerals, such as (Fe 2+ )(Fe 3+ ) 2 (PO 4 ) 2 (OH) 2 (barbosalite) and (Fe 2+ , Mn 2+ )(Fe 3+ ) 2 (PO 4 ) 2 (OH) 2 (lipscombite) [22][23][24][25][26][27][28][29], questions still remain unanswered about the electronic-structural interplay in these compounds. Namely, how the Fe mixed valences control the temperature-dependent properties, how the valence ratio of the Fe ions can be tuned by the synthesis methods [25], etc.…”

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confidence: 99%

Phase Transitions and Physical Properties of the Mixed Valence Iron Phosphate Fe3(PO3OH)4(H2O)4

et al. 2022

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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.

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