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

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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-Fe

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-Fe PubMed

Sivula K., Le Formal F. & Gratzel M. Solar water splitting: Progress using hematite (α-Fe PubMed

Sivula K. 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. PubMed

Zhu Y. H.

Rahman M. M., Jamal A., Khan S. B. & Faisal M. Fabrication of chloroform sensor based on hydrothermally prepared low-dimensional β-Fe

Carraro G. PubMed

Yamamoto T. A.

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

Laurent S. 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.

Gich M.

Namai A. PubMed PMC

Namai A. PubMed

Ohkoshi S. PubMed

Sakurai S., Namai A., Hashimoto K. & Ohkoshi S. First observation of phase transformation of all four Fe PubMed

Lee C. W., Jung S. S. & Lee J. S. Phase transformation of β-Fe

Ito E.

Ono S., Kikegawa T. & Ohishi Y. High-pressure phase transition of hematite, Fe

Ono S. & Ohishi Y. In situ X-ray observation of phase transformation in Fe

Badro J. PubMed

Liu H., Caldwell W. A., Benedetti L. R., Panero W. & Jeanloz R. Static compression of α-Fe

Rozenberg G. K.

Bykova E.

Schouwink P.

Klotz S., Strassle T. & Hansen T. Pressure dependence of Morin transition in alpha-Fe

Pasternak M. P.

Knittle E. & Jeanloz R. High-pressure electrical resistivity measurements of Fe

Ovsyannikov S. V., Morozova N. V., Karkin A. E. & Shchennikov V. V. High-pressure cycling of hematite α-Fe

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.

Wang Z. W. & Saxena S. K. Pressure induced phase transformations in nanocrystalline maghemite (γ-Fe

Jiang J. Z., Olsen J. S., Gerward L. & Mørup S. Enhanced bulk modulus and reduced transition pressure in γ-Fe

Vaidya S. N., Karunakaran C. & Aruna S. T. Effect of high pressure and temperature on nanocrystalline Fe

Zhao J.

Zhang D. M.

Zboril R., Mashlan M. & Krausova D. in Mössbauer Spectroscopy in Materials Science (eds Miglierini M.

Wang Q. 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 SnO

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