View source for Iron(III) oxide

{{short description|Chemical compound}}
{{About|a red-colored oxide of iron|other uses|Red iron (disambiguation){{!}}Red Iron}}
{{Use dmy dates|date=January 2021}}
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 464185021
| Name = Iron(III) oxide
| ImageFile = Haematite-unit-cell-3D-balls.png
| ImageName = Haematite unit cell
| ImageCaption = {{colorbox|#514d7c}} [[Iron|Fe]] {{colorbox|#b20000}} [[Oxygen|O]]
| ImageFile1 = Iron(III)-oxide-sample.jpg
| ImageName1 = Sample of iron(III) oxide
| ImageFile2 = Pourbaix_Diagram_of_Iron.svg
| ImageName2 = Pourbaix Diagram of aqueous Iron
| IUPACName = Iron(III) oxide
| OtherNames = ferric oxide, [[haematite]], ferric iron, red iron oxide, rouge, [[maghemite]], colcothar, iron sesquioxide, [[rust]], [[ochre]]
| SystematicName = 
| Section1 = {{Chembox Identifiers
| CASNo = 1309-37-1
| CASNo_Ref = {{cascite|correct|CAS}}
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = 14147
| UNII = 1K09F3G675
| UNII_Ref = {{fdacite|correct|FDA}}
| ChEBI = 50819
| ChEBI_Ref = {{ebicite|correct|EBI}}
| SMILES = O1[Fe]2O[Fe]1O2
| PubChem = 518696
| RTECS = NO7400000
| KEGG = C19424
| KEGG_Ref = {{keggcite|changed|kegg}}
| InChI = 1/2Fe.3O/rFe2O3/c3-1-4-2(3)5-1
| InChIKey = JEIPFZHSYJVQDO-ZVGCCQCPAC
| StdInChI_Ref = {{stdinchicite|correct|inchi}}
| StdInChI = 1S/2Fe.3O
| StdInChIKey_Ref = {{stdinchicite|correct|inchi}}
| StdInChIKey = JEIPFZHSYJVQDO-UHFFFAOYSA-N
| EC_number = 215-168-2
| Gmelin = 11092
  }}
| Section2 = {{Chembox Properties
| Fe=2 | O=3
| Appearance = Red solid
| Odor = Odorless
| Density = 5.25 g/cm<sup>3</sup><ref name=crc/>
| MeltingPtC = 1539
| MeltingPt_ref = <ref name=crc>[[#Haynes|Haynes]], p. 4.69</ref><br /> decomposes<br /> {{convert|105|C|F K}}<br /> β-dihydrate, decomposes<br /> {{convert|150|C|F K}}<br /> β-monohydrate, decomposes<br /> {{convert|50|C|F K}}<br /> α-dihydrate, decomposes<br /> {{convert|92|C|F K}}<br /> α-monohydrate, decomposes<ref name=doc00>{{cite book|page = 433|title = A Dictionary of Chemical Solubilities: Inorganic|edition = 2nd|first1 = Arthur Messinger|last1 = Comey|first2 = Dorothy A.|last2 = Hahn|place = New York|publisher = The MacMillan Company|date = February 1921|url=https://archive.org/details/dictionaryofchem00comerich/page/436/mode/2up }}</ref>
| Solubility = Insoluble
| SolubleOther = Soluble in diluted [[acid]]s,<ref name=crc /> barely soluble in [[sugar]] solution<ref name=doc00/><br /> Trihydrate slightly soluble in aq. [[tartaric acid]], [[citric acid]], [[acetic acid]]<ref name=doc00 />
| MagSus = +3586.0x10<sup>−6</sup> cm<sup>3</sup>/mol
| RefractIndex = n<sub>1</sub>&nbsp;=&nbsp;2.91, n<sub>2</sub>&nbsp;=&nbsp;3.19 (α, hematite)<ref>[[#Haynes|Haynes]], p. 4.141</ref>
}}
| Section3 = {{Chembox Structure
| CrystalStruct = [[Rhombohedral lattice system|Rhombohedral]], [[pearson symbol|hR30]] (α-form)<ref name=odnpa>{{cite book|page = 167|url = https://books.google.com/books?id=sY-0IGwimWkC&pg=PA167|title = One-Dimensional Nanostructures: Principles and Applications|editor-first = Tianyou|editor-last = Zhai|editor-first2 = Jiannian|editor-last2 = Yao|year = 2013|place = Hoboken, New Jersey|isbn = 978-1-118-07191-5|publisher = John Wiley & Sons, Inc.|first1 = Yichuan|last1 = Ling|first2 = Damon A.|last2 = Wheeler|first3 = Jin Zhong|last3 = Zhang|first4 = Yat|last4 = Li}}</ref><br /> [[cubic crystal system|Cubic]] bixbyite, cI80 (β-form)<br /> Cubic spinel (γ-form)<br /> [[orthorhombic crystal system|Orthorhombic]] (ε-form)<ref name="atmilab" />
| SpaceGroup = R3c, No. 161 (α-form)<ref name=odnpa /><br /> Ia{{overline|3}}, No. 206 (β-form)<br /> Pna2<sub>1</sub>, No. 33 (ε-form)<ref name="atmilab" />
| PointGroup = 3m (α-form)<ref name=odnpa /><br /> 2/m {{overline|3}} (β-form)<br /> mm2 (ε-form)<ref name="atmilab" />
| Coordination = [[octahedral molecular geometry|Octahedral]] (Fe<sup>3+</sup>, α-form, β-form)<ref name=odnpa />
  }}
| Section4 = {{Chembox Thermochemistry
| Thermochemistry_ref =<ref name=crc2>[[#Haynes|Haynes]], p. 5.12</ref>
| DeltaHf = −824.2 kJ/mol<ref name=crc2 />
| DeltaGf = −742.2 kJ/mol<ref name=crc2 />
| Entropy = 87.4 J/mol·K<ref name=crc2 />
| HeatCapacity = 103.9 J/mol·K<ref name=crc2 />
  }}
| Section5 = 
| Section6 = 
| Section7 = {{Chembox Hazards
| GHSPictograms = {{GHS07}}<ref name="sigma">{{Sigma-Aldrich|id=529311|name=Iron(III) oxide|accessdate=2014-07-12}}</ref>
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|315|319|335}}<ref name="sigma" />
| PPhrases = {{P-phrases|261|305+351+338}}<ref name="sigma" />
| NFPA-H = 0
| NFPA-F = 0
| NFPA-R = 0
| NFPA-S = 
| NFPA_ref = <ref name=leker >{{cite web|url = http://www.lesker.com/msds/pdfs/cd72f997d54d3bc42d09a34d6bdca56ebf2ea7fd3a31f08843ec5bd413.pdf|title = SDS of Iron(III) oxide|date = 2012-01-05|publisher = Kurt J Lesker Company Ltd.|place = England|access-date = 2014-07-12|website = KJLC}}</ref>
| TLV-TWA = 5&nbsp;mg/m<sup>3</sup><ref name=crc />
| LD50 = >10 g/kg (rats, oral)<ref name=leker />
| PEL = TWA 10 mg/m<sup>3</sup><ref name=PGCH>{{PGCH|0344}}</ref>
| IDLH = 2500 mg/m<sup>3</sup><ref name=PGCH/>
| REL = TWA 5 mg/m<sup>3</sup><ref name=PGCH/> 
  }}
| Section8 = {{Chembox Related
| OtherAnions = [[Iron(III) fluoride]]
| OtherCations = [[Manganese(III) oxide]]<br /> [[Cobalt(III) oxide]]
| OtherFunction = [[Iron(II) oxide]]<br /> [[Iron(II,III) oxide]]
| OtherFunction_label = [[iron oxides]]
  }}
}}
[[File:Железный сурик.jpg|alt=Vial with iron(III) oxide|thumb|Iron(III) oxide in a vial]]
'''Iron(III) oxide''' or '''ferric oxide''' is the [[inorganic compound]] with the formula {{chem2|Fe2O3}}. It occurs in nature as the mineral [[hematite]], which serves as the primary source of iron for the steel industry. It is also known as '''red iron oxide''', especially when used in [[pigment]]s.

It is one of the three main [[oxide]]s of [[iron]], the other two being [[iron(II) oxide]] (FeO), which is rare; and [[iron(II,III) oxide]] ({{chem2|Fe3O4}}), which also occurs naturally as the mineral [[magnetite]]. 

Iron(III) oxide is often called [[rust]], since rust shares several properties and has a similar composition; however, in chemistry, rust is considered an ill-defined material, described as hydrous ferric oxide.<ref>{{Cite web|last=PubChem|title=Iron oxide (Fe2O3), hydrate|url=https://pubchem.ncbi.nlm.nih.gov/compound/61560|access-date=2020-11-11|website=pubchem.ncbi.nlm.nih.gov|language=en}}</ref>

Ferric oxide is readily attacked by even weak [[acid]]s. It is a weak [[oxidising agent]], most famously when reduced by [[aluminium]] in the [[thermite]] reaction.

==Structure==
{{chem2|Fe2O3}} can be obtained in various [[polymorphism (materials science)|polymorph]]s. In the primary polymorph, α, iron adopts octahedral coordination geometry. That is, each Fe center is bound to six oxygen [[ligand]]s. In the γ polymorph, some of the Fe sit on tetrahedral sites, with four oxygen ligands.

===Alpha phase===
α-{{chem2|Fe2O3}} has the [[rhombohedral lattice system|rhombohedral]], [[aluminium oxide|corundum]] (α-Al<sub>2</sub>O<sub>3</sub>) structure and is the most common form. It occurs naturally as the mineral [[hematite]], which is mined as the main [[ore]] of iron. It is [[antiferromagnetic]] below ~260 K ([[Morin transition]] temperature), and exhibits weak [[ferromagnetism]] between 260 K and the [[Néel temperature]], 950 K.<ref>{{cite book |first=J. E. |last=Greedan |year=1994 |chapter=Magnetic oxides |title=Encyclopedia of Inorganic chemistry |editor-first=R. Bruce |editor-last=King |publisher=John Wiley & Sons |location=New York |isbn=978-0-471-93620-6 }}</ref> It is easy to prepare using both [[thermal decomposition]] and precipitation in the liquid phase. Its magnetic properties are dependent on many factors, e.g., pressure, particle size, and magnetic field intensity.

===Gamma phase===
[[maghemite|γ-Fe<sub>2</sub>O<sub>3</sub>]] has a [[cubic crystal system|cubic]] structure. It is metastable and converted from the alpha phase at high temperatures. It occurs naturally as the mineral [[maghemite]]. It is [[ferromagnetic]] and finds application in recording tapes,<ref name="InorgChem"/> although [[ultrafine particles]] smaller than 10 nanometers are [[superparamagnetic]]. It can be prepared by thermal dehydratation of gamma [[iron(III) oxide-hydroxide]]. Another method involves the careful oxidation of [[iron(II,III) oxide]] (Fe<sub>3</sub>O<sub>4</sub>).<ref name="InorgChem"/> The ultrafine particles can be prepared by thermal decomposition of [[iron(III) oxalate]].

===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}}

===Liquid phase===
Molten {{chem2|Fe2O3}} is expected to have a coordination number of close to 5 oxygen atoms about each iron atom, based on measurements of slightly oxygen deficient supercooled liquid iron oxide droplets, where supercooling circumvents the need for the high oxygen pressures required above the melting point to maintain stoichiometry.<ref name="ShiFeOx2020">{{cite journal |last1=Shi |first1=Caijuan |last2=Alderman |first2=Oliver |last3=Tamalonis |first3=Anthony |last4=Weber |first4=Richard |last5=You |first5=Jinglin |last6=Benmore |first6=Chris |title=Redox-structure dependence of molten iron oxides |journal=Communications Materials |date=2020 |volume=1 |issue=1 |page=80 |doi=10.1038/s43246-020-00080-4 |bibcode=2020CoMat...1...80S |doi-access=free }}</ref>

==Hydrated iron(III) oxides==
Several hydrates of Iron(III) oxide exist.
When alkali is added to solutions of soluble Fe(III) salts, a red-brown gelatinous precipitate forms. This is ''not'' {{chem2|Fe(OH)3}}, but {{chem2|Fe2O3*H2O}} (also written as {{chem2|Fe(O)OH}}).

Several forms of the hydrated oxide of Fe(III) exist as well. The red [[lepidocrocite]] (γ-{{chem2|Fe(O)OH}}) occurs on the outside of [[rusticle]]s, and the orange [[goethite]] (α-{{chem2|Fe(O)OH}}) occurs internally in rusticles.
When {{chem2|Fe2O3}}·H<sub>2</sub>O is heated, it loses its water of hydration. Further heating at {{val|1670|u=K}} converts {{chem2|Fe2O3}} to black {{chem2|Fe3O4}} ({{chem2|Fe^{II}Fe^{III}2O4}}), which is known as the mineral [[magnetite]].

{{chem2|Fe(O)OH}} is soluble in acids, giving {{chem2|[Fe(H2O)6](3+)}}. In concentrated aqueous alkali, {{chem2|Fe2O3}} gives {{chem2|[Fe(OH)6](3-)}}.<ref name="InorgChem">{{cite book|title = Inorganic Chemistry|url = https://archive.org/details/inorganicchemist00hous_159|url-access = limited|edition = 3rd|chapter = Chapter 22: ''d''-block metal chemistry: the first row elements|first1 = Catherine E.|last1 = Housecroft|first2 = Alan G.|last2 = Sharpe|publisher = Pearson|year = 2008|isbn = 978-0-13-175553-6|page = [https://archive.org/details/inorganicchemist00hous_159/page/n754 716]}}</ref>

==Reactions==
The most important reaction is its [[carbothermal reduction]], which gives iron used in steel-making:
:{{chem2|Fe2O3 + 3 CO -> 2 Fe + 3 CO2}}

Another redox reaction is the extremely [[exothermic]] [[thermite]] reaction with [[aluminium]].<ref>{{cite book |last1=Adlam |last2=Price |title=Higher School Certificate Inorganic Chemistry |publisher=Leslie Slater Price |year=1945 }}</ref>
:{{chem2|2 Al + Fe2O3 -> 2 Fe + Al2O3}}

This process is used to weld thick metals such as rails of train tracks by using a ceramic container to funnel the molten iron in between two sections of rail. Thermite is also used in weapons and making small-scale cast-iron sculptures and tools.

Partial reduction with hydrogen at about {{val|400|u=degC}} produces magnetite, a black magnetic material that contains both Fe(III) and Fe(II):<ref name=Brauer/>
:{{chem2|Fe2O3 + H2 -> 2 Fe3O4 + H2O}}

Iron(III) oxide is insoluble in water but dissolves readily in strong acid, e.g., hydrochloric and [[sulfuric acid]]s. It also dissolves well in solutions of chelating agents such as [[EDTA]] and [[oxalic acid]].

Heating iron(III) oxides with other metal oxides or carbonates yields materials known as [[ferrate]]s (ferrate (III)):<ref name=Brauer/>
:{{chem2|ZnO + Fe2O3 -> Zn(FeO2)2}}


==Preparation==
Iron(III) oxide is a product of the oxidation of iron. It can be prepared in the laboratory by electrolyzing a solution of [[sodium bicarbonate]], an inert electrolyte, with an iron anode:
:{{chem2|4 Fe + 3 O2 + 2 H2O -> 4 FeO(OH)}}

The resulting hydrated iron(III) oxide, written here as {{chem2|FeO(OH)}}, dehydrates around {{val|200|u=degC}}.<ref name=Brauer>Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1661.</ref><ref name=Ullmann/>
:{{chem2|2 FeO(OH) -> Fe2O3 + H2O}}

==Uses==

===Iron industry===
The overwhelming application of iron(III) oxide is as the feedstock of the steel and iron industries, e.g., the [[smelting|production of iron]], steel, and many alloys.<ref name=Ullmann>{{cite book |last1=Greenwood |first1=N. N. |last2=Earnshaw |first2=A. |year=1997 |title=Chemistry of the Element |edition=2nd |location=Oxford |publisher=Butterworth-Heinemann |isbn=978-0-7506-3365-9 }}</ref> Iron oxide (Fe2O3) has been used in stained glass since the medieval period, with evidence suggesting its use in stained glass production dating back to the early Middle Ages, where it was primarily used to create yellow, orange, and red colors in the glass, still being used for industrial purposes today.<ref>{{Cite web |last=Golchha |first=Vipul |title=About Iron Oxide Pigments |url=https://www.golchhaoxides.com/iron-oxide-pigments.php#:~:text=Iron%20Oxides%20have%20been%20used,drawings%20to%20ensure%20bountiful%20hunting. |access-date=2024-10-29 |website=Golchha Oxides Pvt Ltd |language=en}}</ref><ref>{{Cite web |title=Iron(III) Oxide - Structure, Properties, Uses of Fe2O3 |url=https://byjus.com/chemistry/fe2o3/#:~:text=Ferric%20oxide%20(Fe2O,glass,%20diamonds%20and%20precious%20metals. |access-date=2024-10-29 |website=BYJUS |language=en}}</ref>

===Polishing===
A very fine powder of ferric oxide is known as "jeweler's rouge", "red rouge", or simply rouge. It is used to put the final polish on metallic [[jewellery|jewelry]] and [[lens (optics)|lenses]], and historically as a [[rouge (cosmetics)|cosmetic]]. Rouge cuts more slowly than some modern polishes, such as [[cerium(IV) oxide]], but is still used in optics fabrication and by jewelers for the superior finish it can produce. When polishing gold, the rouge slightly stains the gold, which contributes to the appearance of the finished piece. Rouge is sold as a powder, paste, laced on polishing cloths, or solid bar (with a [[wax]] or [[petroleum|grease]] binder). Other polishing compounds are also often called "rouge", even when they do not contain iron oxide. Jewelers remove the residual rouge on jewelry by use of [[ultrasonic cleaning]]. Products sold as "[[stropping (blade)|stropping]] compound" are often applied to a [[razor strop|leather strop]] to assist in getting a razor edge on knives, straight razors, or any other edged tool.

===Pigment===
{{multiple image|align = left
| footer = Sample of the red α- and yellow β-phases of hydrated of iron(III) oxide;<ref name=doc00 /> both are useful as pigments.
| width1 = 220|image1 = Iron oxide red y.jpg
| width2 = 178|image2 = Iron oxide yellow.jpg
}}
Iron(III) oxide is also used as a [[pigment]], under names "Pigment Brown 6", "Pigment Brown 7", and "Pigment Red 101".<ref>{{cite book |title=Paint and Surface Coatings: Theory and Practice |publisher=William Andrew Inc. |isbn=978-1-884207-73-0 |year= 1999}}</ref> Some of them, e.g., Pigment Red 101 and Pigment Brown 6, are approved by the US [[Food and Drug Administration]] (FDA) for use in cosmetics. [[Iron oxides]] are used as pigments in dental composites alongside titanium oxides.<ref>{{cite book|last=Banerjee|first=Avijit|title=Pickard's Manual of Operative Dentistry|year=2011|publisher=Oxford University Press Inc., New York|location=United States|isbn=978-0-19-957915-0|pages=89}}</ref>

Hematite is the characteristic component of the Swedish paint color [[Falu red]].

===Magnetic recording===
Iron(III) oxide was the most common [[magnet]]ic particle used in all types of [[magnetic storage|magnetic storage and recording]] media, including magnetic disks (for data storage) and [[magnetic tape]] (used in audio and video recording as well as data storage). Its use in computer disks was superseded by cobalt alloy, enabling thinner magnetic films with higher storage density.<ref>{{cite journal|doi=10.1063/1.2750414|title=Perpendicular recording media for hard disk drives|journal=Journal of Applied Physics|volume=102|issue=1|pages=011301–011301–22|year=2007|last1=Piramanayagam|first1=S. N.|bibcode=2007JAP...102a1301P}}</ref>

===Photocatalysis===
α-{{chem2|Fe2O3}} has been studied as a [[photoanode]] for solar water oxidation.<ref name=Kay2006>{{cite journal|author=Kay, A. |author2=Cesar, I. |author3=Grätzel, M.|title=New Benchmark for Water Photooxidation by Nanostructured α-Fe<sub>2</sub>O<sub>3</sub> Films |journal=Journal of the American Chemical Society |volume=128 |issue=49 |pages=15714–15721 |doi=10.1021/ja064380l |pmid=17147381 |year=2006 }}</ref> However, its efficacy is limited by a short diffusion length (2–4&nbsp;nm) of photo-excited charge carriers<ref>{{cite journal|author=Kennedy, J.H.|author2=Frese, K.W.|title=Photooxidation of Water at α-Fe<sub>2</sub>O<sub>3</sub> Electrodes|journal=Journal of the Electrochemical Society|volume=125|issue=5|pages=709|doi=10.1149/1.2131532|year=1978|bibcode=1978JElS..125..709K }}</ref> and subsequent fast [[Electron-hole recombination|recombination]], requiring a large [[overpotential]] to drive the reaction.<ref>{{cite journal|author=Le Formal, F. |title=Back Electron–Hole Recombination in Hematite Photoanodes for Water Splitting |journal=Journal of the American Chemical Society |volume=136 |issue=6 |pages=2564–2574 |doi=10.1021/ja412058x |pmid=24437340 |year=2014 |doi-access=free }}</ref> Research has been focused on improving the water oxidation performance of {{chem2|Fe2O3}} using nanostructuring,<ref name=Kay2006 /> surface functionalization,<ref>{{cite journal|author=Zhong, D.K. |author2=Gamelin, D.R.|title=Photoelectrochemical Water Oxidation by Cobalt Catalyst ("Co−Pi")/α-Fe<sub>2</sub>O<sub>3</sub> Composite Photoanodes: Oxygen Evolution and Resolution of a Kinetic Bottleneck |journal=Journal of the American Chemical Society |volume=132 |issue=12 |pages=4202–4207 |doi=10.1021/ja908730h |pmid=20201513 |year=2010 }}</ref> or by employing alternate crystal phases such as β-{{chem2|Fe2O3}}.<ref>{{cite journal|author=Emery, J.D. |title=Atomic Layer Deposition of Metastable β-Fe<sub>2</sub>O<sub>3</sub> via Isomorphic Epitaxy for Photoassisted Water Oxidation|journal=ACS Applied Materials & Interfaces|volume=6|issue=24|pages=21894–21900|doi=10.1021/am507065y|pmid=25490778|year=2014|osti=1355777}}</ref>

===Medicine===
[[Calamine]] lotion, used to treat mild [[itch]]iness, is chiefly composed of a combination of [[zinc oxide]], acting as [[astringent]], and about 0.5% iron(III) oxide, the product's active ingredient, acting as [[antipruritic]]. The red color of iron(III) oxide is also mainly responsible for the lotion's pink color.

==See also==
* [[Chalcanthum]]
{{Clear}}

==References==
{{reflist}}

==Cited sources==
*{{cite book | ref=Haynes | editor= Haynes, William M. | year = 2011 | title = CRC Handbook of Chemistry and Physics | edition = 92nd | publisher = [[CRC Press]] | isbn = 978-1439855119| title-link = CRC Handbook of Chemistry and Physics }}

==External links==
{{Commons category|Iron(III) oxide|position=left}}
* [https://www.cdc.gov/niosh/npg/npgd0344.html NIOSH Pocket Guide to Chemical Hazards]

{{Iron compounds}}
{{Oxides}}
{{Metal metabolism}}

{{DEFAULTSORT:Iron(Iii) Oxide}}
[[Category:E-number additives]]
[[Category:Iron oxide pigments]]
[[Category:Iron(III) compounds]]
[[Category:Transition metal oxides]]
[[Category:Sesquioxides]]