Editing Iron(III) oxide (section)

===Other solid phases===
Several other phases have been identified or claimed. The beta phase (β-phase) is cubic body-centered (space group Ia3), [[Metastability|metastable]], and at temperatures above {{convert|500|°C|°F|-1|abbr=on|lk=off}} converts to alpha phase. It can be prepared by reduction of hematite by carbon,{{Clarify|reason=reduction implies Fe(II) but it should still be Fe(III)|date=October 2020}} [[pyrolysis]] of [[iron(III) chloride]] solution, or thermal decomposition of [[iron(III) sulfate]].<ref>{{Cite web|title=Mechanism of Oxidation & Thermal Decomposition of Iron Sulphides|url=https://core.ac.uk/download/pdf/298011553.pdf}}</ref>

The epsilon (ε) phase is rhombic, and shows properties intermediate between alpha and gamma, and may have useful magnetic properties applicable for purposes such as high density [[magnetic storage|recording media]] for [[big data]] storage.<ref>{{cite journal |title=Advances in magnetic films of epsilon-iron oxide toward next-generation high-density recording media |url=https://pubs.rsc.org/en/content/articlelanding/2021/dt/d0dt03460f |journal=Dalton Transactions |year=2021 |publisher=Royal Society of Chemistry |doi=10.1039/D0DT03460F |access-date=25 January 2021|last1=Tokoro |first1=Hiroko |last2=Namai |first2=Asuka |last3=Ohkoshi |first3=Shin-Ichi |volume=50 |issue=2 |pages=452–459 |pmid=33393552 |s2cid=230482821 |url-access=subscription }}</ref> Preparation of the pure epsilon phase has proven very challenging. Material with a high proportion of epsilon phase can be prepared by thermal transformation of the gamma phase. The epsilon phase is also metastable, transforming to the alpha phase at between {{convert|500|and|750|°C|°F|-1|abbr=on|lk=off}}. It can also be prepared by oxidation of iron in an [[electric arc]] or by [[sol-gel]] precipitation from [[iron(III) nitrate]].{{Citation needed|date=July 2011}} Research has revealed epsilon iron(III) oxide in ancient Chinese [[Jian ware|Jian ceramic]] glazes, which may provide insight into ways to produce that form in the lab.<ref>{{cite journal|doi=10.1038/srep04941 |pmid=24820819 |pmc=4018809 |title=Learning from the past: Rare ε-Fe<sub>2</sub>O<sub>3</sub> in the ancient black-glazed Jian (Tenmoku) wares |journal=Scientific Reports |volume=4 |pages=4941 |year=2015 |last1=Dejoie |first1=Catherine |last2=Sciau |first2=Philippe |last3=Li |first3=Weidong |last4=Noé |first4=Laure |last5=Mehta |first5=Apurva |last6=Chen |first6=Kai |last7=Luo |first7=Hongjie |last8=Kunz |first8=Martin |last9=Tamura |first9=Nobumichi |last10=Liu |first10=Zhi }}</ref>{{Primary source inline|date=October 2020}}

Additionally, at high pressure an [[amorphous]] form is claimed.<ref name="atmilab">{{cite web|url = http://atmilab.upol.cz/texty/ultrafine02.pdf|access-date = 2014-07-12|title = Ultrafine Particles of Iron(III) Oxides by View of AFM – Novel Route for Study of Polymorphism in Nano-world|first1 = Milan|last1 = Vujtek|first2 = Radek|last2 = Zboril|first3 = Roman|last3 = Kubinek|first4 = Miroslav|last4 = Mashlan|website = Univerzity Palackého}}</ref>{{Primary source inline|date=October 2020}}