Iron(III) oxide shows a polymorphism, characteristic of existence of phases with the same chemical composition but distinct crystal structures and, hence, physical properties. Four crystalline phases of iron(III) oxide have previously been identified: α-Fe2O3 (hematite), β-Fe2O3, γ-Fe2O3 (maghemite), and ε-Fe2O3. All four iron(III) oxide phases easily undergo various phase transformations in response to heating or pressure treatment, usually forming hexagonal α-Fe2O3, which is the most thermodynamically stable Fe2O3 polymorph under ambient conditions. Here, from synchrotron X-ray diffraction experiments, we report the formation of a new iron(III) oxide polymorph that we have termed ζ-Fe2O3 and which evolved during pressure treatment of cubic β-Fe2O3 (Ia3 space group) at pressures above 30 GPa. Importantly, ζ-Fe2O3 is maintained after pressure release and represents the first monoclinic Fe2O3 polymorph (I2/a space group) that is stable at atmospheric pressure and room temperature. ζ-Fe2O3 behaves as an antiferromagnet with a Néel transition temperature of ~69 K. The complex mechanism of pressure-induced transformation of β-Fe2O3, involving also the formation of Rh2O3-II-type Fe2O3 and post-perovskite-Fe2O3 structure, is suggested and discussed with respect to a bimodal size distribution of precursor nanoparticles.

Department of Chemistry School of Science The University of Tokyo 7 3 1 Hongo Bunkyo ku Tokyo 113 0033 Japan

Regional Centre of Advanced Technologies and Materials Departments of Physical Chemistry and Experimental Physics Faculty of Science Palacky University Slechtitelu 27 783 71 Olomouc Czech Republic

Research and Development Center for Ocean Drilling Science Japan Agency for Marine Earth Science and Technology 2 15 Natsushima cho Yokosuka shi Kanagawa 237 0061 Japan

See more in PubMed

Cornell R. M. & Schwertmann U. The Iron Oxides: Structure, Properties, Reactions, Occurrence and Uses. Wiley-VCH Publishers, Weinheim, Germany, 2003.

Zboril R., Mashlan M. & Petridis D. Iron(III) oxides from thermal processes-synthesis, structural and magnetic properties, Mössbauer spectroscopy characterization, and applications. Chem. Mater. 14, 969–982 (2002).

Tucek J., Zboril R. & Petridis D. Maghemite nanoparticles by view of Mössbauer spectroscopy. J. Nanosci. Nanotechnol. 6, 926–947 (2006). PubMed

Tucek J., Zboril R., Namai A. & Ohkoshi S. ε-Fe2O3: An advanced nanomaterial exhibiting giant coercive field, millimeter-wave ferromagnetic resonance, and magnetoelectric coupling. Chem. Mater. 22, 6483–6505 (2010).

Machala L., Tucek J. & Zboril R. Polymorphous transformations of nanometric iron(III) oxide: A review. Chem. Mater. 23, 3255–3272 (2011).

Jin J., Ohkoshi S. & Hashimoto K. Giant coercive field of nanometer-sized iron oxide. Adv. Mater. 16, 48–51 (2004).

Kay A., Cesar I. & Gratzel M. New benchmark for water photooxidation by nanostructured alpha-Fe2O3 films. J. Am. Chem. Soc. 128, 15714–15721 (2006). PubMed

Sivula K., Le Formal F. & Gratzel M. Solar water splitting: Progress using hematite (α-Fe2O3) photoelectrodes. ChemSusChem 4, 432–449 (2011). PubMed

Sivula K. et al. Photoelectrochemical water splitting with mesoporous hematite prepared by a solution-based colloidal approach. J. Am. Chem. Soc. 132, 7436–7444 (2010). PubMed

Hermanek M., Zboril R., Medrik I., Pechousek J. & Gregor C. Catalytic efficiency of iron(III) oxides in decomposition of hydrogen peroxide: Competition between the surface area and crystallinity of nanoparticles. J. Am. Chem. Soc. 129, 10929–10936 (2007). PubMed

Polshettiwar V. et al. Magnetically recoverable nanocatalysts. Chem. Rev. 111, 3036–3075 (2011). PubMed

Zhu Y. H. et al. Magnetic nanocomposites: A new perspective in catalysis. ChemCatChem 2, 365–374 (2010).

Rahman M. M., Jamal A., Khan S. B. & Faisal M. Fabrication of chloroform sensor based on hydrothermally prepared low-dimensional β-Fe2O3 nanoparticles. Superlattices Microstruct. 50, 369–376 (2011).

Carraro G. et al. Vapor-phase fabrication of β-iron oxide nanopyramids for lithium-ion battery anodes. ChemPhysChem 13, 3798–3801 (2012). PubMed

Yamamoto T. A. et al. Dependence of the magnetocaloric effect in superparamagnetic nanocomposites on the distribution of magnetic moment size. Scripta Mater. 46, 89–94 (2002).

Gupta A. K. & Gupta M. Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications. Biomaterials 26, 3995–4021 (2005). PubMed

Laurent S. et al. Magnetic iron oxide nanoparticles: Synthesis, stabilization, vectorization, physicochemical characterizations, and biological applications. Chem. Rev. 108, 2064–2110 (2008). PubMed

Lu A. H., Salabas E. L. & Schuth F. Magnetic nanoparticles: Synthesis, protection, functionalization, and application. Angew. Chem. Int. Ed. 46, 1222–1244 (2007). PubMed

Urbanova V. et al. Nanocrystalline iron oxides, composites, and related materials as a platform for electrochemical, magnetic, and chemical biosensors. Chem. Mater. 26, 6653–6673 (2014)

Gich M. et al. Magnetoelectric coupling in ε-Fe2O3 nanoparticles. Nanotechnology 17, 687–691 (2006).

Namai A. et al. Hard magnetic ferrite with a gigantic coercivity and high frequency millimetre wave rotation. Nat. Commun. 3, 1035 (2012). PubMed PMC

Namai A. et al. Synthesis of an electromagnetic wave absorber for high-speed wireless communication. J. Am. Chem. Soc. 131, 1170–1173 (2009). PubMed

Ohkoshi S. et al. A millimeter-wave absorber based on gallium-substituted ε-iron oxide nanomagnets. Angew. Chem. Int. Ed. 46, 8392–8395 (2007). PubMed

Sakurai S., Namai A., Hashimoto K. & Ohkoshi S. First observation of phase transformation of all four Fe2O3 phases (γ-> ε-> β-> α-phase). J. Am. Chem. Soc. 131, 18299–18303 (2009). PubMed

Lee C. W., Jung S. S. & Lee J. S. Phase transformation of β-Fe2O3 hollow nanoparticles. Mater. Lett. 62, 561–563 (2008).

Ito E. et al. Determination of high-pressure phase equilibria of Fe2O3 using the Kawai-type apparatus equipped with sintered diamond anvils. Am. Mineral. 94, 205–209 (2009).

Ono S., Kikegawa T. & Ohishi Y. High-pressure phase transition of hematite, Fe2O3. J. Phys. Chem. Solids 65, 1527–1530 (2004).

Ono S. & Ohishi Y. In situ X-ray observation of phase transformation in Fe2O3 at high pressures and high temperatures. J. Phys. Chem. Solids 66, 1714–1720 (2005).

Badro J. et al. Nature of the high-pressure transition in Fe2O3 hematite. Phys. Rev. Lett. 89, 205504 (2002). PubMed

Liu H., Caldwell W. A., Benedetti L. R., Panero W. & Jeanloz R. Static compression of α-Fe2O3: Linear incompressibility of lattice parameters and high-pressure transformations. Phys. Chem. Miner. 30, 582–588 (2003).

Rozenberg G. K. et al. High-pressure structural studies of hematite Fe2O3. Phys. Rev. B 65, 064112 (2002).

Bykova E. et al. L. Novel high pressure monoclinic Fe2O3 polymorph revealed by single-crystal synchrotron X-ray diffraction studies. High Pressure Res. 33, 534–545 (2013).

Schouwink P. et al. High-pressure structural behavior of α-Fe2O3 studied by single-crystal X-ray diffraction and synchrotron radiation up to 25 GPa. Am. Mineral. 96, 1781–1786 (2011).

Klotz S., Strassle T. & Hansen T. Pressure dependence of Morin transition in alpha-Fe2O3 hematite. EPL 104, 16001 (2013).

Pasternak M. P. et al. Breakdown of the Mott-Hubbard state in Fe2O3: A first-order insulator-metal transition with collapse of magnetism at 50 GPa. Phys. Rev. Lett. 82, 4663–4666 (1999).

Knittle E. & Jeanloz R. High-pressure electrical resistivity measurements of Fe2O3: Comparison of static-compression and shock-wave experiments to 61 GPa. Solid State Commun. 58, 129–131 (1986).

Ovsyannikov S. V., Morozova N. V., Karkin A. E. & Shchennikov V. V. High-pressure cycling of hematite α-Fe2O3: Nanostructuring, in situ electronic transport, and possible charge disproportionation. Phys. Rev. B 86, 205131 (2012).

Clark S. M., Prilliman S. G., Erdonmez C. K. & Alivisatos A. P. Size dependence of the pressure-induced gamma to alpha structural phase transition in iron oxide nanocrystals. Nanotechnology 16, 2813–2818 (2005).

Kawakami T. et al. Mössbauer spectroscopy of pressure-induced phase transformation from maghemite to hematite. J. Phys. Soc. Jpn. 72, 2640–2645 (2003).

Wang Z. W. & Saxena S. K. Pressure induced phase transformations in nanocrystalline maghemite (γ-Fe2O3). Solid State Commun. 123, 195–200 (2002).

Jiang J. Z., Olsen J. S., Gerward L. & Mørup S. Enhanced bulk modulus and reduced transition pressure in γ-Fe2O3 nanocrystals. Europhys. Lett. 44, 620–626 (1998).

Vaidya S. N., Karunakaran C. & Aruna S. T. Effect of high pressure and temperature on nanocrystalline Fe2O3 and TiO2. High Pressure Res. 21, 79–92 (2001).

Zhao J. et al. High bulk modulus of nanocrystal γ-Fe2O3 with chemical dodecyl benzene sulfonic decoration under high pressure. Chin. Phys. Lett. 17, 126–128 (2000).

Zhang D. M. et al. Electrical property of nanocrystalline γ-Fe2O3 under high pressure. Physica B 407, 1044–1046 (2012).

Zboril R., Mashlan M. & Krausova D. in Mössbauer Spectroscopy in Materials Science (eds Miglierini M. et al. ) 49–56 (Springer, Dordrecht, The Netherlands, 1999).

Wang Q. et al. Unusual compression behavior of nanocrystalline CeO2. Sci. Rep. 4, 4441 (2014). PubMed PMC

Samara G. A. & Giardini A. A. Effect of pressure on the Néel temperature of magnetite. Phys. Rev. 186, 577–580 (1969).

Ono S., Ohishi Y. & Kikegawa T. High-pressure study of rhombohedral iron oxide, FeO, at pressures between 41 and 142 GPa. J. Phys. Condens. Matter 19, 036205 (2007).

Dorogokupets P. I. & Oganov A. R. Ruby, metals, and MgO as alternative pressure scales: A semiempirical description of shock-wave, ultrasonic, X-ray, and thermochemical data at high temperatures and pressures. Phys. Rev. B 75, 024115 (2007).

Ono S., Funakoshi K., Nozawa A. & Kikegawa T. High-pressure phase transitions in SnO2. J. Appl. Phys. 97, 073523 (2005).

Δ-FeOOH as Support for Immobilization Peroxidase: Optimization via a Chemometric Approach