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{{infobox indium}} | {{infobox indium}} | ||
'''Indium''' is a [[chemical element]]; | '''Indium''' is a [[chemical element]]; its [[Symbol (chemistry)|symbol]] is '''In''' and its [[atomic number]] is 49. It is a silvery-white [[post-transition metal]] and one of the softest elements. Chemically, indium is similar to [[gallium]] and [[thallium]], and its properties are largely intermediate between the two. It was discovered in 1863 by [[Ferdinand Reich]] and [[Hieronymous Theodor Richter]] by [[spectroscope|spectroscopic methods]] and named for the [[indigo]] blue line in its spectrum.<ref>{{Cite web |title=Indium {{!}} In (Element) - PubChem |url=https://pubchem.ncbi.nlm.nih.gov/element/Indium |access-date=2025-09-12 |website=pubchem.ncbi.nlm.nih.gov}}</ref> | ||
Indium is used primarily in the production of [[flat-panel display]]s as [[indium tin oxide]] (ITO), a transparent and conductive coating applied to glass. {{ | Indium is used primarily in the production of [[flat-panel display]]s as [[indium tin oxide]] (ITO), a transparent and conductive coating applied to [[glass]].<ref>{{Cite web |title=Indium Tin Oxide Targets for Mobile Phone and Tablet Display Screens |url=https://www.samaterials.com/blog/indium-tin-oxide-targets-for-mobile-phone-and-tablet-display-screens.html |access-date=2025-09-12 |website=www.samaterials.com |language=en}}</ref> It is also used in the [[semiconductor industry]], in low-melting-point metal [[alloys]] such as [[Solder#Alloying element roles|solders]] and soft-metal high-vacuum seals.<ref>{{Cite patent|number=US4153317A|title=Indium seal for gas laser|gdate=1979-05-08|invent1=Ljung|invent2=Koper|inventor1-first=Bo H. G.|inventor2-first=James G.|url=https://patents.google.com/patent/US4153317A/en}}</ref> It is used in the manufacture of blue and white [[LED circuit|LED circuits]], mainly to produce [[Indium gallium nitride]] p-type semiconductor substrates.<ref name="j486">{{cite web | title=Why It Was Almost Impossible to Make the Blue LED | website=YouTube | date=2024-03-06 | url=https://www.youtube.com/watch?v=AF8d72mA41M&t=1430s | access-date=2025-08-15}}</ref> It is produced exclusively as a [[by-product]] during the processing of the ores of other metals, chiefly from [[sphalerite]] and other [[zinc]] [[Sulfide mineral|sulfide ores]].<ref name="Frenzel-2017" /> | ||
Indium has no biological role and its compounds are toxic when inhaled or injected into the bloodstream, although they are poorly absorbed following ingestion. {{ | Indium has no biological role and its compounds are toxic when inhaled or injected into the bloodstream, although they are poorly absorbed following ingestion.<ref>"[https://app.croneri.co.uk/first-aid-guide/indium-and-compounds?topic=742 Indium and compounds]{{Dead link|date=May 2026 |bot=InternetArchiveBot }}". ''app.croneri.co.uk''. Retrieved 2025-09-12.</ref><ref>Bomhard, Ernst. (2018). [https://www.researchgate.net/publication/323007985_The_toxicology_of_indium_oxide The toxicology of indium oxide]. Environmental Toxicology and Pharmacology. 58. 10.1016/j.etap.2018.02.003.</ref> | ||
==Etymology== | ==Etymology== | ||
The name comes from the [[Latin]] word ''indicum'' meaning [[Violet (color)|violet]] or [[indigo]].<ref>Royal Society of Chemistry | The name comes from the [[Latin]] word ''indicum'' meaning [[Violet (color)|violet]] or [[indigo]].<ref>{{Cite web |title=The Royal Society of Chemistry |url=https://www.rsc.org/ |access-date=2026-05-28 |website=Royal Society of Chemistry |language=en}}</ref> The word ''indicum'' means "Indian", as the naturally based dye [[Indigo dye|indigo]] was originally exported to Europe from [[India]]. | ||
==Properties== | ==Properties== | ||
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===Physical=== | ===Physical=== | ||
[[File:Indium wetting glass.jpg|thumb|left|Indium wetting the glass surface of a test tube]] | [[File:Indium wetting glass.jpg|thumb|left|Indium wetting the glass surface of a test tube]] | ||
Indium is a shiny silvery-white, highly [[ductile]] [[post-transition metal]] with a bright [[Lustre (mineralogy)|luster]].<ref name="InProcess">{{cite journal|last=Alfantazi|first=A. M.|date=2003|title=Processing of indium: a review|journal=Minerals Engineering|volume=16|issue=8|pages=687–694|doi=10.1016/S0892-6875(03)00168-7|author2=Moskalyk, R. R.|bibcode=2003MiEng..16..687A }}</ref> It is so soft ([[Mohs hardness]] 1.2) that it can be cut with a knife | Indium is a shiny silvery-white, highly [[ductile]] [[post-transition metal]] with a bright [[Lustre (mineralogy)|luster]].<ref name="InProcess">{{cite journal|last=Alfantazi|first=A. M.|date=2003|title=Processing of indium: a review|journal=Minerals Engineering|volume=16|issue=8|pages=687–694|doi=10.1016/S0892-6875(03)00168-7|author2=Moskalyk, R. R.|bibcode=2003MiEng..16..687A }}</ref> It is so soft ([[Mohs hardness]] 1.2) that it can be cut with a knife or be bitten into by [[human teeth]]. Indium also leaves a visible line like a pencil when rubbed on paper.<ref name="Binder">{{cite book |last=Binder |first=Harry H. |date=1999 |title=Lexicon der chemischen Elemente |publisher=S. Hirzel Verlag |isbn=978-3-7776-0736-8 |language=de }}</ref> It is a member of [[boron group|group 13]] on the [[periodic table]] and its properties are mostly intermediate between its vertical neighbors [[gallium]] and [[thallium]]. As with [[tin]], a high-pitched [[tin cry|cry]] is heard when indium is bent – a crackling sound due to [[crystal twinning]].<ref name="InProcess" /> Like gallium, indium is able to [[wetting|wet]] glass and has a low [[melting point]], 156.60 °C (313.88 °F); higher than its lighter homologue, gallium, but lower than its heavier homologue, thallium, and lower than tin.<ref name="Lange">{{cite book |last=Dean |first=John A. |title=Lange's handbook of chemistry |publisher=McGraw-Hill, Inc.|date=523|isbn=978-0-07-016190-0|edition=Fifteenth }}</ref> The boiling point is 2072 °C (3762 °F), higher than that of thallium, but lower than gallium, conversely to the general trend of melting points, but similarly to the trends down the other post-transition metal groups because of the weakness of the metallic bonding with few [[Delocalized electron|electrons delocalized]].<ref name="Greenwood222">Greenwood and Earnshaw, p. 222</ref> | ||
The density of indium, 7.31 g/cm<sup>3</sup>, is also greater than gallium, but lower than thallium. Below the [[critical temperature]], 3.41 [[kelvin|K]], indium becomes a [[superconductor]]. Indium crystallizes in the body-centered [[tetragonal crystal system]] in the [[space group]] ''I''4/''mmm'' ([[lattice parameter]]s: ''a'' = 325 [[picometer|pm]], ''c'' = 495 pm):<ref name="Lange" /> this is a slightly distorted [[face-centered cubic]] structure, where each indium atom has four neighbours at 324 pm distance and eight neighbours slightly further (336 pm).<ref name="Greenwood252">Greenwood and Earnshaw, p. 252</ref> Indium has greater solubility in liquid mercury than any other metal (more than 50 mass percent of indium at 0 °C).<ref>{{Cite journal|title=Hg-In phase diagram|journal=Journal of Phase Equilibria and Diffusion|volume=33|issue=2|pages=159–160|doi=10.1007/s11669-012-9993-3|year=2012|last1=Okamoto|first1=H.|s2cid=93043767}}</ref> Indium displays a ductile [[Viscoplasticity|viscoplastic]] response, found to be size-independent in tension and compression. However it does have a [[Size effect on structural strength|size effect]] in bending and indentation, associated to a length-scale of order 50–100 μm,<ref>{{Cite journal|last1=Iliev|first1=S. P.|last2=Chen|first2=X.|last3=Pathan|first3=M. V.|last4=Tagarielli|first4=V. L.|date=2017-01-23|title=Measurements of the mechanical response of Indium and of its size dependence in bending and indentation|journal=Materials Science and Engineering: A|volume=683|pages=244–251|doi=10.1016/j.msea.2016.12.017|hdl=10044/1/43082|hdl-access=free}}</ref> significantly large when compared with other metals. | The density of indium, 7.31 g/cm<sup>3</sup>, is also greater than gallium, but lower than thallium. Below the [[critical temperature]], 3.41 [[kelvin|K]], indium becomes a [[superconductor]]. Indium crystallizes in the body-centered [[tetragonal crystal system]] in the [[space group]] ''I''4/''mmm'' ([[lattice parameter]]s: ''a'' = 325 [[picometer|pm]], ''c'' = 495 pm):<ref name="Lange" /> this is a slightly distorted [[face-centered cubic]] structure, where each indium atom has four neighbours at 324 pm distance and eight neighbours slightly further (336 pm).<ref name="Greenwood252">Greenwood and Earnshaw, p. 252</ref> Indium has greater solubility in liquid mercury than any other metal (more than 50 mass percent of indium at 0 °C).<ref>{{Cite journal|title=Hg-In phase diagram|journal=Journal of Phase Equilibria and Diffusion|volume=33|issue=2|pages=159–160|doi=10.1007/s11669-012-9993-3|year=2012|last1=Okamoto|first1=H.|s2cid=93043767}}</ref> Indium displays a ductile [[Viscoplasticity|viscoplastic]] response, found to be size-independent in tension and compression. However it does have a [[Size effect on structural strength|size effect]] in bending and indentation, associated to a length-scale of order 50–100 μm,<ref>{{Cite journal|last1=Iliev|first1=S. P.|last2=Chen|first2=X.|last3=Pathan|first3=M. V.|last4=Tagarielli|first4=V. L.|date=2017-01-23|title=Measurements of the mechanical response of Indium and of its size dependence in bending and indentation|journal=Materials Science and Engineering: A|volume=683|pages=244–251|doi=10.1016/j.msea.2016.12.017|hdl=10044/1/43082|hdl-access=free}}</ref> significantly large when compared with other metals. | ||
=== | ===Isotopes=== | ||
Indium has 49 electrons, with an electronic configuration of [[[krypton|Kr]]]4d{{sup|10}}5s{{sup|2}}5p{{sup|1}}. In compounds, indium most commonly donates the three outermost electrons to become indium(III), In{{sup|3+}}. In some cases, the pair of 5s-electrons are not donated, resulting in indium(I), In{{sup|+}}. The stabilization of the [[valence (chemistry)|monovalent]] state is attributed to the [[inert pair effect]], in which [[relativistic quantum chemistry|relativistic effects]] | {{Main|Isotopes of indium}} | ||
Indium has 39 known [[isotope]]s, ranging in [[mass number]] from 97 to 135. Only two isotopes occur naturally as [[primordial nuclide]]s: indium-113, the only [[stable isotope]], and indium-115, which has a [[half-life]] of 4.41{{e|14}} years, four orders of magnitude greater than the [[age of the Universe]] and nearly 30,000 times greater than half-life of [[thorium-232]].<ref name="Audi">{{NUBASE 2003}}</ref> The half-life of <sup>115</sup>In is very long because the [[beta decay]] to <sup>115</sup>[[tin|Sn]] is [[selection rule|spin-forbidden]].<ref>{{cite journal |last1=Dvornický |first1=R. |last2=Šimkovic |first2=F. |date=13–16 June 2011 |title=Second unique forbidden β decay of <sup>115</sup>In and neutrino mass |journal=AIP Conf. Proc. |volume=1417 |issue=33 |page=33 |doi=10.1063/1.3671032|series=AIP Conference Proceedings |bibcode=2011AIPC.1417...33D }}</ref> Indium-115 makes up 95.7% of all indium. Indium is one of three known elements (the others being [[tellurium]] and [[rhenium]]) of which the stable isotope is less abundant in nature than the long-lived primordial radioisotopes.<ref>{{cite web |url=http://www.ciaaw.org/pubs/Periodic_Table_Isotopes.pdf |title=IUPAC Periodic Table of the Isotopes |date=1 October 2013 |website=ciaaw.org |publisher=[[IUPAC]] |access-date=21 June 2016 |archive-date=14 February 2019 |archive-url=https://web.archive.org/web/20190214115238/http://www.ciaaw.org/pubs/Periodic_Table_Isotopes.pdf |url-status=live }}</ref> | |||
The stablest [[synthetic radioisotope|artificial]] isotope is [[indium-111]], with a half-life of approximately 2.8 days. All other isotopes have half-lives shorter than 5 hours. Indium also has 47 meta states, among which indium-114m1 (half-life about 49.51 days) is the most stable, more stable than the ground state of any indium isotope other than the primordial. All decay by [[isomeric transition]]. The indium isotopes lighter than <sup>113</sup>In predominantly decay through [[electron capture]] or [[positron emission]] to form [[cadmium]] isotopes, while the indium isotopes heavier than <sup>113</sup>In predominantly decay through beta-minus decay to form tin isotopes.<ref name="Audi" /> | |||
==Chemistry== | |||
Indium has 49 electrons, with an electronic configuration of [[[krypton|Kr]]]4d{{sup|10}}5s{{sup|2}}5p{{sup|1}}. In compounds, indium most commonly donates the three outermost electrons to become indium(III), In{{sup|3+}}. In some cases, the pair of 5s-electrons are not donated, resulting in indium(I), In{{sup|+}}. The stabilization of the [[valence (chemistry)|monovalent]] state is attributed to the [[inert pair effect]], in which [[relativistic quantum chemistry|relativistic effects]] lowers the energy of the 5s-orbital, observed in heavier elements. [[Thallium]] (indium's heavier [[Homologous series|homolog]]) shows an even stronger effect, manifested by the pervasiveness of thallium(I) vs thallium(III),<ref>{{cite book|publisher = Walter de Gruyter|date = 1985|edition = 91–100|pages = 892–893|isbn = 978-3-11-007511-3|title = Lehrbuch der Anorganischen Chemie|first = Arnold F.|last = Holleman|author2 = Wiberg, Egon |author3 = Wiberg, Nils|chapter =Thallium|language=de}}</ref> Gallium (indium's lighter homolog) is only rarely observed in the +1 oxidation state. Thus, although thallium(III) is a moderately strong [[oxidizing agent]], indium(III) is not, and many indium(I) compounds are powerful [[reducing agent]]s.<ref name="G&E">{{Greenwood&Earnshaw2nd}}</ref> While the energy required to include the s-electrons in chemical bonding is lowest for indium among the group 13 metals, bond energies decrease down the group so that by indium, the energy released in forming two additional bonds and attaining the +3 state is not always enough to outweigh the energy needed to involve the 5s-electrons.<ref name="Greenwood256">Greenwood and Earnshaw, p. 256</ref> Indium(I) oxide and hydroxide are more basic and indium(III) oxide and hydroxide are more acidic.<ref name="Greenwood256" /> | |||
A number of standard electrode potentials, depending on the reaction under study,<ref>{{RubberBible92nd|page=8.20}}</ref> are reported for indium, reflecting the decreased stability of the +3 oxidation state:<ref name="Greenwood252" /> | A number of standard electrode potentials, depending on the reaction under study,<ref>{{RubberBible92nd|page=8.20}}</ref> are reported for indium, reflecting the decreased stability of the +3 oxidation state:<ref name="Greenwood252" /> | ||
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Indium metal does not react with water, but it is oxidized by stronger oxidizing agents such as [[halogen]]s to give indium(III) compounds. It does not form a [[boride]], [[silicide]], or [[carbide]] | Indium metal does not react with water, but it is oxidized by stronger [[Oxidizing agent|oxidizing agents]] such as [[halogen]]s to give indium(III) compounds. It does not form a [[boride]], [[silicide]], or [[carbide]]. | ||
Indium is rather basic in aqueous solution, showing only slight [[amphoteric]] characteristics, and unlike its lighter homologs aluminium and gallium, it is insoluble in aqueous alkaline solutions.<ref name="Greenwood255">Greenwood and Earnshaw, p. 255</ref> | |||
=== | ===Indium(III) compounds=== | ||
{{ | {{See also|Indium chalcogenides|Category:Indium compounds}} | ||
[[File:Kristallstruktur Chrom(III)-chlorid.png|thumb|right|upright=1|[[Indium trichloride|InCl<sub>3</sub>]] ''(structure pictured)'' is a common compound of indium.]] | |||
== | ====Hydrides and halides==== | ||
{{ | The hydride [[Indium trihydride|InH<sub>3</sub>]] has at best a transitory existence in [[ether]]eal solutions at low temperatures. It polymerizes in the absence of bases.<ref name="G&E" /> [[Lewis base]]s stabilize a rich collection of indium hydrides of the formula LInH<sub>3</sub> (L = [[tertiary phosphine]] and [[N-Heterocyclic carbene]]s).<ref name=EIBC>{{cite book |last1=Zhao |first1=Yanbao |last2=Zhang |first2=Zhijun |title=Encyclopedia of Inorganic and Bioinorganic Chemistry |chapter=Indium: Inorganic Chemistry|date=2005 |doi=10.1002/9781119951438.eibc0090 |isbn=978-1-119-95143-8 }}</ref> | ||
Chlorination, bromination, and iodination of In produce colorless [[indium(III) chloride|InCl<sub>3</sub>]], [[indium(III) bromide|InBr<sub>3</sub>]], and yellow InI<sub>3</sub>. The compounds are [[Lewis acid]]s, somewhat akin to the better known aluminium trihalides. Again like the related aluminium compound, InF<sub>3</sub> is polymeric.<ref name="Greenwood263">Greenwood and Earnshaw, pp. 263–7</ref> | |||
[[ | |||
[[ | |||
Indium halides dissolves in water to give aquo complexes such as [In(H<sub>2</sub>O)<sub>6</sub>]<sup>3+</sup> and [InCl<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>]<sup>+</sup>. Similar complexes can be prepared from nitrates and acetates. Overall, the pattern is similar to that for aluminium(III).<ref name=EIBC/> | |||
====Chalcogenides and pnictides==== | |||
Indium derivatives of chalcogenides (O, S, Se, Te) are well developed. [[Indium(III) oxide]], In<sub>2</sub>O<sub>3</sub>, forms when indium metal is burned in air or when the hydroxide or nitrate is heated.<ref name="downs">{{Cite book| title = Chemistry of aluminium, gallium, indium, and thallium| author = Anthony John Downs| publisher = Springer| year = 1993| isbn = 978-0-7514-0103-5}}</ref> The analogous sesqui-chalcogenides with [[sulfur]], [[selenium]], and [[tellurium]] are also known.<ref name="Greenwood286">Greenwood and Earnshaw, p. 286</ref> | |||
The chemistry of indium pnictides (N, P, As, Sb) is also well known, motivated by their relevance to [[semiconductor]] technology. For applications in microelectronics, the P, As, and Sb derivatives are made by reactions of [[trimethylindium]]: | |||
:{{chem2|In(CH3)3 + H3E -> InE + 3 CH4}} (E = P, As, Sb) | |||
Many of these derivatives are prone to hydrolysis.<ref name="Greenwood288">Greenwood and Earnshaw, p. 288</ref> | |||
===Indium(I)=== | ===Indium(I) compounds=== | ||
Indium(I) compounds are not common. The chloride, [[indium(I) bromide|bromide]], and iodide are deeply colored, unlike the parent trihalides from which they are prepared. The fluoride is known only as an unstable gas.<ref name="Greenwood270">Greenwood and Earnshaw, pp. 270–1</ref> Indium(I) oxide black powder is produced when indium(III) oxide decomposes upon heating to 700 °C.<ref name="downs" /> | Indium(I) compounds are not common. The chloride, [[indium(I) bromide|bromide]], and iodide are deeply colored, unlike the parent trihalides from which they are prepared. The fluoride is known only as an unstable gas.<ref name="Greenwood270">Greenwood and Earnshaw, pp. 270–1</ref> Indium(I) oxide black powder is produced when indium(III) oxide decomposes upon heating to 700 °C.<ref name="downs" /> | ||
=== | ===Compounds in other oxidation states=== | ||
Less frequently, indium forms compounds in oxidation state +2 and even fractional oxidation states. Usually such materials feature In–In bonding, most notably in the [[indium halides|halides]] In<sub>2</sub>X<sub>4</sub> and [In<sub>2</sub>X<sub>6</sub>]<sup>2−</sup>,<ref name="can82">{{cite journal| doi =10.1139/v82-102| title =Neutral complexes of the indium dihalides| date =1982| last1 =Sinclair| first1 =Ian| last2 =Worrall| first2 =Ian J.| journal =Canadian Journal of Chemistry| volume =60| issue =6| pages =695–698| doi-access =free}}</ref> and various subchalcogenides such as In<sub>4</sub>Se<sub>3</sub>.<ref name="Greenwood287">Greenwood and Earnshaw, p. 287</ref> Several other compounds are known to combine indium(I) and indium(III), such as In<sup>I</sup><sub>6</sub>(In<sup>III</sup>Cl<sub>6</sub>)Cl<sub>3</sub>,<ref>{{cite journal |doi = 10.1002/anie.199108241 |title = In7Cl9—A New"Old" Compound in the System In-Cl |date = 1991 |last1 = Beck |first1 = Horst Philipp |last2 = Wilhelm |first2 = Doris |journal = Angewandte Chemie International Edition in English |volume = 30 |issue = 7 |pages = 824–825}}</ref> In<sup>I</sup><sub>5</sub>(In<sup>III</sup>Br<sub>4</sub>)<sub>2</sub>(In<sup>III</sup>Br<sub>6</sub>),<ref>{{cite journal| doi =10.1002/anie.199511261| title =Synthesis, Structure, and Decay of In4Br7| date =1995| last1 =Dronskowski| first1 =Richard| journal =Angewandte Chemie International Edition in English| volume =34| issue =10| pages =1126–1128}}</ref> and In<sup>I</sup>In<sup>III</sup>Br<sub>4</sub>.<ref name="can82" /> | Less frequently, indium forms compounds in oxidation state +2 and even fractional oxidation states. Usually such materials feature In–In bonding, most notably in the [[indium halides|halides]] In<sub>2</sub>X<sub>4</sub> and [In<sub>2</sub>X<sub>6</sub>]<sup>2−</sup>,<ref name="can82">{{cite journal| doi =10.1139/v82-102| title =Neutral complexes of the indium dihalides| date =1982| last1 =Sinclair| first1 =Ian| last2 =Worrall| first2 =Ian J.| journal =Canadian Journal of Chemistry| volume =60| issue =6| pages =695–698| doi-access =free}}</ref> and various subchalcogenides such as In<sub>4</sub>Se<sub>3</sub>.<ref name="Greenwood287">Greenwood and Earnshaw, p. 287</ref> Several other compounds are known to combine indium(I) and indium(III), such as In<sup>I</sup><sub>6</sub>(In<sup>III</sup>Cl<sub>6</sub>)Cl<sub>3</sub>,<ref>{{cite journal |doi = 10.1002/anie.199108241 |title = In7Cl9—A New"Old" Compound in the System In-Cl |date = 1991 |last1 = Beck |first1 = Horst Philipp |last2 = Wilhelm |first2 = Doris |journal = Angewandte Chemie International Edition in English |volume = 30 |issue = 7 |pages = 824–825}}</ref> In<sup>I</sup><sub>5</sub>(In<sup>III</sup>Br<sub>4</sub>)<sub>2</sub>(In<sup>III</sup>Br<sub>6</sub>),<ref>{{cite journal| doi =10.1002/anie.199511261| title =Synthesis, Structure, and Decay of In4Br7| date =1995| last1 =Dronskowski| first1 =Richard| journal =Angewandte Chemie International Edition in English| volume =34| issue =10| pages =1126–1128}}</ref> and In<sup>I</sup>In<sup>III</sup>Br<sub>4</sub>.<ref name="can82" /> | ||
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In 1863, German chemists [[Ferdinand Reich]] and [[Hieronymous Theodor Richter|Hieronymus Theodor Richter]] were testing ores from the mines around [[Freiberg, Saxony]]. They dissolved the minerals [[pyrite]], [[arsenopyrite]], [[galena]] and [[sphalerite]] in [[hydrochloric acid]] and distilled raw [[zinc chloride]]. Reich, who was [[color-blind]], employed Richter as an assistant for detecting the colored spectral lines. Knowing that ores from that region sometimes contain [[thallium]], they searched for the green thallium emission spectrum lines. Instead, they found a bright blue line. Because that blue line did not match any known element, they hypothesized a new element was present in the minerals. They named the element indium, from the [[indigo]] color seen in its spectrum, after the Latin ''indicum'', meaning 'of [[India]]'.<ref>{{cite journal|title = Ueber das Indium|author = Reich, F.|author2 = Richter, T.|journal = Journal für Praktische Chemie|volume = 90|issue = 1|pages = 172–176|date = 1863|doi = 10.1002/prac.18630900122|s2cid = 94381243|language = de|url = https://zenodo.org/record/1427838|access-date = 2019-06-30|archive-date = 2020-02-02|archive-url = https://web.archive.org/web/20200202154729/https://zenodo.org/record/1427838|url-status = live}}</ref><ref name="Venetskii">{{cite journal|title = Indium|last = Venetskii|first = S.|journal = Metallurgist|volume = 15|issue = 2|pages = 148–150|date = 1971|doi = 10.1007/BF01088126}}</ref><ref name="Greenwood244">Greenwood and Earnshaw, p. 244</ref><ref name="Weeks">{{cite journal|author=Weeks, Mary Elvira |author-link=Mary Elvira Weeks |title=The Discovery of the Elements: XIII. Some Spectroscopic Studies |journal=Journal of Chemical Education |volume=9 |issue=8 |pages=1413–1434 |url=http://search.jce.divched.org/JCEIndex/FMPro?-db=jceindex.fp5&-lay=wwwform&combo=weeks&-find=&-format=detail.html&-skip=27&-max=1&-token.2=27&-token.3=10 |doi=10.1021/ed009p1413 |year=1932 |bibcode=1932JChEd...9.1413W |url-access=subscription }}{{dead link|date=April 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> | In 1863, German chemists [[Ferdinand Reich]] and [[Hieronymous Theodor Richter|Hieronymus Theodor Richter]] were testing ores from the mines around [[Freiberg, Saxony]]. They dissolved the minerals [[pyrite]], [[arsenopyrite]], [[galena]] and [[sphalerite]] in [[hydrochloric acid]] and distilled raw [[zinc chloride]]. Reich, who was [[color-blind]], employed Richter as an assistant for detecting the colored spectral lines. Knowing that ores from that region sometimes contain [[thallium]], they searched for the green thallium emission spectrum lines. Instead, they found a bright blue line. Because that blue line did not match any known element, they hypothesized a new element was present in the minerals. They named the element indium, from the [[indigo]] color seen in its spectrum, after the Latin ''indicum'', meaning 'of [[India]]'.<ref>{{cite journal|title = Ueber das Indium|author = Reich, F.|author2 = Richter, T.|journal = Journal für Praktische Chemie|volume = 90|issue = 1|pages = 172–176|date = 1863|doi = 10.1002/prac.18630900122|s2cid = 94381243|language = de|url = https://zenodo.org/record/1427838|access-date = 2019-06-30|archive-date = 2020-02-02|archive-url = https://web.archive.org/web/20200202154729/https://zenodo.org/record/1427838|url-status = live}}</ref><ref name="Venetskii">{{cite journal|title = Indium|last = Venetskii|first = S.|journal = Metallurgist|volume = 15|issue = 2|pages = 148–150|date = 1971|doi = 10.1007/BF01088126}}</ref><ref name="Greenwood244">Greenwood and Earnshaw, p. 244</ref><ref name="Weeks">{{cite journal|author=Weeks, Mary Elvira |author-link=Mary Elvira Weeks |title=The Discovery of the Elements: XIII. Some Spectroscopic Studies |journal=Journal of Chemical Education |volume=9 |issue=8 |pages=1413–1434 |url=http://search.jce.divched.org/JCEIndex/FMPro?-db=jceindex.fp5&-lay=wwwform&combo=weeks&-find=&-format=detail.html&-skip=27&-max=1&-token.2=27&-token.3=10 |doi=10.1021/ed009p1413 |year=1932 |bibcode=1932JChEd...9.1413W |url-access=subscription }}{{dead link|date=April 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> | ||
Richter went on to isolate the metal in 1864.<ref>{{cite journal|title = Ueber das Indium|author = Reich, F.|author2=Richter, T.|journal = Journal für Praktische Chemie|volume = 92 |issue = 1 |pages = 480–485 |date = 1864|doi = 10.1002/prac.18640920180|language=de}}</ref> An ingot of {{convert|0.5|kg|lb|abbr=on}} was presented at the [[Exposition Universelle (1867)|World Fair]] 1867.<ref name="SchSch">{{cite book|title = Indium: Geology, Mineralogy, and Economics|first = Ulrich|last = Schwarz-Schampera|author2=Herzig, Peter M.|publisher = Springer|date = 2002|isbn = 978-3-540-43135-0|url = https://books.google.com/books?id=k7x_2_KnupMC&pg=PA1}}</ref> <!-- Until 1924, only approximately a gram of indium constituted the world's supply.<ref name=g1>{{cite journal|doi =10.1063/1.1769802|title =New Materials|year =1941|last1 =Olpin|first1 = A. R.|journal =Review of Scientific Instruments|volume =12|page =560|issue =11|bibcode = 1941RScI...12..560O }}</ref><ref name=g2>{{cite book|url=https://books.google.com/books?id=QdU-lRMjOsgC&pg=PA24|title=Infectious diseases and pathology of reptiles: color atlas and text|author=Jacobson, E. R.|page=24|publisher=CRC Press|year=2007|isbn=0-8493-2321-5}}</ref> --> Reich and Richter later fell out when | Richter went on to isolate the metal in 1864.<ref>{{cite journal|title = Ueber das Indium|author = Reich, F.|author2=Richter, T.|journal = Journal für Praktische Chemie|volume = 92 |issue = 1 |pages = 480–485 |date = 1864|doi = 10.1002/prac.18640920180|language=de}}</ref> An ingot of {{convert|0.5|kg|lb|abbr=on}} was presented at the [[Exposition Universelle (1867)|World Fair]] 1867.<ref name="SchSch">{{cite book|title = Indium: Geology, Mineralogy, and Economics|first = Ulrich|last = Schwarz-Schampera|author2=Herzig, Peter M.|publisher = Springer|date = 2002|isbn = 978-3-540-43135-0|url = https://books.google.com/books?id=k7x_2_KnupMC&pg=PA1}}</ref> <!-- Until 1924, only approximately a gram of indium constituted the world's supply.<ref name=g1>{{cite journal|doi =10.1063/1.1769802|title =New Materials|year =1941|last1 =Olpin|first1 = A. R.|journal =Review of Scientific Instruments|volume =12|page =560|issue =11|bibcode = 1941RScI...12..560O }}</ref><ref name=g2>{{cite book|url=https://books.google.com/books?id=QdU-lRMjOsgC&pg=PA24|title=Infectious diseases and pathology of reptiles: color atlas and text|author=Jacobson, E. R.|page=24|publisher=CRC Press|year=2007|isbn=0-8493-2321-5}}</ref> --> Reich and Richter later fell out when Richter claimed to be the sole discoverer.<ref name="Weeks" /> | ||
==Occurrence== | ==Occurrence== | ||
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Indium is the [[Abundance of elements in Earth's crust|68th most abundant element in Earth's crust]] at approximately 50 [[parts per billion|ppb]]. This is similar to the crustal abundance of [[silver]], [[bismuth]] and [[Mercury (element)|mercury]]. It very rarely forms its own minerals, or occurs in elemental form. Fewer than 10 indium minerals such as [[roquesite]] (CuInS<sub>2</sub>) are known, and none occur at sufficient concentrations for economic extraction.<ref name="Frenzel-2016">{{Cite journal|url=https://www.researchgate.net/publication/309583931|title=The distribution of gallium, germanium and indium in conventional and non-conventional resources - Implications for global availability (PDF Download Available)|website=ResearchGate|doi=10.13140/rg.2.2.20956.18564|access-date=2017-06-02|year=2016|last1=Frenzel|first1=Max|archive-date=2018-10-06|archive-url=https://web.archive.org/web/20181006235214/https://www.researchgate.net/publication/309583931|url-status=live}}</ref> Instead, indium is usually a trace constituent of more common ore minerals, such as [[sphalerite]] and [[chalcopyrite]].<ref>{{Cite journal|last1=Frenzel|first1=Max|last2=Hirsch|first2=Tamino|last3=Gutzmer|first3=Jens|date=July 2016|title=Gallium, germanium, indium, and other trace and minor elements in sphalerite as a function of deposit type — A meta-analysis|journal=Ore Geology Reviews|volume=76|pages=52–78|doi=10.1016/j.oregeorev.2015.12.017|bibcode=2016OGRv...76...52F }}</ref><ref>{{Cite journal|last1=Bachmann|first1=Kai|last2=Frenzel|first2=Max|last3=Krause|first3=Joachim|last4=Gutzmer|first4=Jens|date=June 2017|title=Advanced Identification and Quantification of In-Bearing Minerals by Scanning Electron Microscope-Based Image Analysis|journal=Microscopy and Microanalysis|volume=23|issue=3|pages=527–537|doi=10.1017/S1431927617000460|pmid=28464970|issn=1431-9276|bibcode=2017MiMic..23..527B|s2cid=6751828}}</ref> From these, it can be extracted as a [[by-product]] during smelting.<ref name="Frenzel-2017">{{Cite journal|last1=Frenzel|first1=Max|last2=Mikolajczak|first2=Claire|last3=Reuter|first3=Markus A.|last4=Gutzmer|first4=Jens|date=June 2017|title=Quantifying the relative availability of high-tech by-product metals – The cases of gallium, germanium and indium|journal=Resources Policy|volume=52|pages=327–335|doi=10.1016/j.resourpol.2017.04.008|bibcode=2017RePol..52..327F |doi-access=free}}</ref> While the enrichment of indium in these deposits is high relative to its crustal abundance, it is insufficient, at current prices, to support extraction of indium as the main product.<ref name="Frenzel-2016" /> | Indium is the [[Abundance of elements in Earth's crust|68th most abundant element in Earth's crust]] at approximately 50 [[parts per billion|ppb]]. This is similar to the crustal abundance of [[silver]], [[bismuth]] and [[Mercury (element)|mercury]]. It very rarely forms its own minerals, or occurs in elemental form. Fewer than 10 indium minerals such as [[roquesite]] (CuInS<sub>2</sub>) are known, and none occur at sufficient concentrations for economic extraction.<ref name="Frenzel-2016">{{Cite journal|url=https://www.researchgate.net/publication/309583931|title=The distribution of gallium, germanium and indium in conventional and non-conventional resources - Implications for global availability (PDF Download Available)|website=ResearchGate|doi=10.13140/rg.2.2.20956.18564|access-date=2017-06-02|year=2016|last1=Frenzel|first1=Max|archive-date=2018-10-06|archive-url=https://web.archive.org/web/20181006235214/https://www.researchgate.net/publication/309583931|url-status=live}}</ref> Instead, indium is usually a trace constituent of more common ore minerals, such as [[sphalerite]] and [[chalcopyrite]].<ref>{{Cite journal|last1=Frenzel|first1=Max|last2=Hirsch|first2=Tamino|last3=Gutzmer|first3=Jens|date=July 2016|title=Gallium, germanium, indium, and other trace and minor elements in sphalerite as a function of deposit type — A meta-analysis|journal=Ore Geology Reviews|volume=76|pages=52–78|doi=10.1016/j.oregeorev.2015.12.017|bibcode=2016OGRv...76...52F }}</ref><ref>{{Cite journal|last1=Bachmann|first1=Kai|last2=Frenzel|first2=Max|last3=Krause|first3=Joachim|last4=Gutzmer|first4=Jens|date=June 2017|title=Advanced Identification and Quantification of In-Bearing Minerals by Scanning Electron Microscope-Based Image Analysis|journal=Microscopy and Microanalysis|volume=23|issue=3|pages=527–537|doi=10.1017/S1431927617000460|pmid=28464970|issn=1431-9276|bibcode=2017MiMic..23..527B|s2cid=6751828}}</ref> From these, it can be extracted as a [[by-product]] during smelting.<ref name="Frenzel-2017">{{Cite journal|last1=Frenzel|first1=Max|last2=Mikolajczak|first2=Claire|last3=Reuter|first3=Markus A.|last4=Gutzmer|first4=Jens|date=June 2017|title=Quantifying the relative availability of high-tech by-product metals – The cases of gallium, germanium and indium|journal=Resources Policy|volume=52|pages=327–335|doi=10.1016/j.resourpol.2017.04.008|bibcode=2017RePol..52..327F |doi-access=free}}</ref> While the enrichment of indium in these deposits is high relative to its crustal abundance, it is insufficient, at current prices, to support extraction of indium as the main product.<ref name="Frenzel-2016" /> | ||
Different estimates exist of the amounts of indium contained within the ores of other metals.<ref name="USGSCS2007">{{cite web|url= | Different estimates exist of the amounts of indium contained within the ores of other metals.<ref name="USGSCS2007">{{cite web|url=https://minerals.usgs.gov/minerals/pubs/commodity/indium/indiumcs07.pdf|title=Mineral Commodities Summary 2007: Indium|publisher=United States Geological Survey|access-date=2007-12-26|archive-date=2008-05-09|archive-url=https://web.archive.org/web/20080509184325/http://minerals.usgs.gov/minerals/pubs/commodity/indium/indiumcs07.pdf|url-status=live}}</ref><ref>{{Cite journal|last1=Werner|first1=T. T.|last2=Mudd|first2=G. M.|last3=Jowitt|first3=S. M.|date=2015-10-02|title=Indium: key issues in assessing mineral resources and long-term supply from recycling|journal=Applied Earth Science|volume=124|issue=4|pages=213–226|doi=10.1179/1743275815Y.0000000007|bibcode=2015ApEaS.124..213W |s2cid=128555024|issn=0371-7453}}</ref> However, these amounts are not extractable without mining of the host materials (see Production and availability). Thus, the availability of indium is fundamentally determined by the ''rate'' at which these ores are extracted, and not their absolute amount. This is an aspect that is often forgotten in the current debate, e.g. by the Graedel group at Yale in their criticality assessments,<ref>{{Cite journal|last1=Graedel|first1=T. E.|last2=Barr|first2=Rachel|last3=Chandler|first3=Chelsea|last4=Chase|first4=Thomas|last5=Choi|first5=Joanne|last6=Christoffersen|first6=Lee|last7=Friedlander|first7=Elizabeth|last8=Henly|first8=Claire|last9=Jun|first9=Christine|date=2012-01-17|title=Methodology of Metal Criticality Determination|journal=Environmental Science & Technology|volume=46|issue=2|pages=1063–1070|doi=10.1021/es203534z|pmid=22191617|issn=0013-936X|bibcode=2012EnST...46.1063G}}</ref> explaining the paradoxically low depletion times some studies cite.<ref>{{Cite journal|last1=Harper|first1=E. M.|last2=Kavlak|first2=Goksin|last3=Burmeister|first3=Lara|last4=Eckelman|first4=Matthew J.|last5=Erbis|first5=Serkan|last6=Sebastian Espinoza|first6=Vicente|last7=Nuss|first7=Philip|last8=Graedel|first8=T. E.|date=2015-08-01|title=Criticality of the Geological Zinc, Tin, and Lead Family|journal=Journal of Industrial Ecology|volume=19|issue=4|pages=628–644|doi=10.1111/jiec.12213|bibcode=2015JInEc..19..628H |s2cid=153380535|issn=1530-9290|url=http://hdl.handle.net/10.1111/jiec.2015.19.issue-4|url-access=subscription}}{{Dead link|date=October 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="Frenzel-2017" /> | ||
==Production and availability== | ==Production and availability== | ||
[[File:Indium world production.svg|thumb|World production trend<ref>[ | [[File:Indium world production.svg|thumb|World production trend<ref>[https://minerals.usgs.gov/minerals/pubs/historical-statistics/ U.S. Geological Survey – Historical Statistics for Mineral and Material Commodities in the United States]; [https://minerals.usgs.gov/minerals/pubs/historical-statistics/ds140-indiu.pdf INDIUM STATISTICS] // USGS, April 1, 2014</ref>]] | ||
Indium is produced exclusively as a [[by-product]] during the processing of the ores of other metals. Its main source material are sulfidic zinc ores, where it is mostly hosted by sphalerite.<ref name="Frenzel-2017" /> Minor amounts are also extracted from sulfidic copper ores. During the [[Zinc smelting|roast-leach-electrowinning process of zinc smelting]], indium accumulates in the iron-rich residues. From these, it can be extracted in different ways. It may also be recovered directly from the process solutions. Further purification is done by [[electrolysis]].<ref name="Greenwood247">Greenwood and Earnshaw, p. 247</ref> The exact process varies with the mode of operation of the smelter.<ref name="InProcess" /><ref name="Frenzel-2017" /> | Indium is produced exclusively as a [[by-product]] during the processing of the ores of other metals. Its main source material are sulfidic zinc ores, where it is mostly hosted by sphalerite.<ref name="Frenzel-2017" /> Minor amounts are also extracted from sulfidic copper ores. During the [[Zinc smelting|roast-leach-electrowinning process of zinc smelting]], indium accumulates in the iron-rich residues. From these, it can be extracted in different ways. It may also be recovered directly from the process solutions. Further purification is done by [[electrolysis]].<ref name="Greenwood247">Greenwood and Earnshaw, p. 247</ref> The exact process varies with the mode of operation of the smelter.<ref name="InProcess" /><ref name="Frenzel-2017" /> | ||
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China is a leading producer of indium (290 tonnes in 2016), followed by South Korea (195 t), Japan (70 t) and Canada (65 t).<ref name="USGS-2017" /> The [[Teck Resources]] refinery in [[Trail, British Columbia]], is a large single-source indium producer, with an output of 32.5 tonnes in 2005, 41.8 tonnes in 2004 and 36.1 tonnes in 2003. | China is a leading producer of indium (290 tonnes in 2016), followed by South Korea (195 t), Japan (70 t) and Canada (65 t).<ref name="USGS-2017" /> The [[Teck Resources]] refinery in [[Trail, British Columbia]], is a large single-source indium producer, with an output of 32.5 tonnes in 2005, 41.8 tonnes in 2004 and 36.1 tonnes in 2003. | ||
The primary consumption of indium worldwide is [[ | The primary consumption of indium worldwide is [[liquid-crystal display|LCD]] production. Demand rose rapidly from the late 1990s to 2010 with the popularity of LCD computer monitors and television sets, which now account for 50% of indium consumption.<ref name=":0">{{cite web|title = Indium Price Supported by LCD Demand and New Uses for the Metal|work = Geology.com|format = PDF|url = http://geology.com/articles/indium.shtml|access-date = 2007-12-26|archive-url = https://web.archive.org/web/20071221130320/http://geology.com/articles/indium.shtml|archive-date = 2007-12-21}}</ref> Increased manufacturing efficiency and recycling (especially in Japan) maintain a balance between demand and supply. According to the [[UNEP]], indium's end-of-life recycling rate is less than 1%.<ref name="USGS2011">{{cite web|title=USGS Mineral Commodity Summaries 2011|url=https://minerals.usgs.gov/minerals/pubs/mcs/2011/mcs2011.pdf|publisher=USGS and USDI|access-date=August 2, 2011|archive-date=January 11, 2019|archive-url=https://web.archive.org/web/20190111211631/https://minerals.usgs.gov/minerals/pubs/mcs/2011/mcs2011.pdf|url-status=live}}</ref> | ||
==Applications== | ==Applications== | ||
===Industrial uses=== | ===Industrial uses=== | ||
[[File:Dell axim LCD under microscope.jpg|thumb|right|A magnified image of an [[TFT LCD|LCD]] screen showing RGB pixels. Individual transistors are seen as white dots in the bottom part.]] | [[File:Dell axim LCD under microscope.jpg|thumb|right|A magnified image of an [[TFT LCD|LCD]] screen showing RGB pixels. Individual transistors are seen as white dots in the bottom part.]] | ||
In 1924, indium was found to have a valued property of stabilizing [[non-ferrous metals]], and that became the first significant use for the element.<ref name="dd">{{cite journal |doi = 10.1021/ed011p270 |title = A story of indium |date = 1934 |last1 = French |first1 = Sidney J. |journal = Journal of Chemical Education |volume = 11 |issue = 5 |page = 270|bibcode = 1934JChEd..11..270F }}</ref> The first large-scale application for indium was coating [[bearing (mechanical)|bearings]] in high-performance [[aircraft]] engines during [[World War II]], to protect against damage and [[corrosion]]; this is no longer a major use of the element.<ref name="Greenwood247" /> New uses were found in [[fusible alloy]]s, [[solder]]s, and [[electronics]]. In the 1950s, tiny beads of indium were used for the emitters and collectors of PNP [[alloy-junction transistor]]s. In the middle and late 1980s, the development of [[indium phosphide]] [[semiconductor]]s and [[indium tin oxide]] thin films for [[liquid-crystal display]]s (LCD) aroused much interest. By 1992, the thin-film application had become the largest end use.<ref name="USGSYB2007">{{cite web|title = Mineral Yearbook 2007: Indium|publisher = United States Geological Survey|first = Amy C.|last = Tolcin|url = | In 1924, indium was found to have a valued property of stabilizing [[non-ferrous metals]], and that became the first significant use for the element.<ref name="dd">{{cite journal |doi = 10.1021/ed011p270 |title = A story of indium |date = 1934 |last1 = French |first1 = Sidney J. |journal = Journal of Chemical Education |volume = 11 |issue = 5 |page = 270|bibcode = 1934JChEd..11..270F }}</ref> The first large-scale application for indium was coating [[bearing (mechanical)|bearings]] in high-performance [[aircraft]] engines during [[World War II]], to protect against damage and [[corrosion]]; this is no longer a major use of the element.<ref name="Greenwood247" /> New uses were found in [[fusible alloy]]s, [[solder]]s, and [[electronics]]. In the 1950s, tiny beads of indium were used for the emitters and collectors of PNP [[alloy-junction transistor]]s. In the middle and late 1980s, the development of [[indium phosphide]] [[semiconductor]]s and [[indium tin oxide]] thin films for [[liquid-crystal display]]s (LCD) aroused much interest. By 1992, the thin-film application had become the largest end use.<ref name="USGSYB2007">{{cite web|title = Mineral Yearbook 2007: Indium|publisher = United States Geological Survey|first = Amy C.|last = Tolcin|url = https://minerals.usgs.gov/mineralofthemonth/indium.pdf|access-date = 2009-12-03|archive-date = 2016-12-31|archive-url = https://web.archive.org/web/20161231013853/https://minerals.usgs.gov/mineralofthemonth/indium.pdf|url-status = live}}</ref><ref name="Downs">{{cite book|title = Chemistry of Aluminium, Gallium, Indium, and Thallium |first =Anthony John|last = Downs|publisher = Springer|date = 1993|isbn = 978-0-7514-0103-5|pages = 89 and 106|url = https://books.google.com/books?id=v-04Kn758yIC}}</ref> | ||
Indium(III) oxide and [[indium tin oxide]] (ITO) are used as a [[transparency (optics)|transparent]] [[electrical conductor|conductive]] coating on [[glass]] substrates in [[electroluminescent]] panels.<ref>{{cite web|title=The Electroluminescent Light Sabre |work=Nanotechnology News Archive |publisher=Azonano |date=June 2, 2005 |url=http://azonano.com/news.asp?newsID=1007 |access-date=2007-08-29 |archive-url=https://web.archive.org/web/20071012003936/http://azonano.com/news.asp?newsID=1007 |archive-date=October 12, 2007 }}</ref> Indium tin oxide is used as | Indium(III) oxide and [[indium tin oxide]] (ITO) are used as a [[transparency (optics)|transparent]] [[electrical conductor|conductive]] coating on [[glass]] substrates in [[electroluminescent]] panels.<ref>{{cite web|title=The Electroluminescent Light Sabre |work=Nanotechnology News Archive |publisher=Azonano |date=June 2, 2005 |url=http://azonano.com/news.asp?newsID=1007 |access-date=2007-08-29 |archive-url=https://web.archive.org/web/20071012003936/http://azonano.com/news.asp?newsID=1007 |archive-date=October 12, 2007 }}{{dead link|date=August 2025}}</ref> Indium tin oxide is used as an [[infrared radiation]] filter in [[sodium-vapor lamp#Low-pressure sodium|low-pressure sodium-vapor lamps]]. The infrared radiation is reflected back into the lamp, which increases the temperature within the tube and improves the performance of the lamp.<ref name="Downs" /> | ||
Indium has many [[semiconductor]]-related applications. Some indium compounds, such as [[indium antimonide]] and [[indium phosphide]],<ref>{{cite journal|title = Properties, Preparation, and Device Applications of Indium Phosphide|journal = [[Annual Review of Materials Science]]|volume = 11|pages = 441–484|date = 1981|doi = 10.1146/annurev.ms.11.080181.002301|first = K. J.|last = Bachmann|bibcode = 1981AnRMS..11..441B }}</ref> are [[semiconductor]]s with useful properties: one precursor is usually [[trimethylindium]] (TMI), which is also used as the [[semiconductor]] [[dopant]] in II–VI [[compound semiconductor]]s.<ref name="shenai2004" /> InAs and InSb are used for low-temperature transistors and InP for high-temperature transistors.<ref name="Greenwood247" /> The [[compound semiconductor]]s [[InGaN]] and [[InGaP]] are used in [[light-emitting diode]]s (LEDs) and laser diodes.<ref>{{cite book|isbn=978-0-521-53351-5|title=Light-Emitting Diodes|author=Schubert, E. Fred |date=2003|page=16|publisher=Cambridge University Press}}</ref> Indium is used in [[photovoltaics]] as the semiconductor [[copper indium gallium selenide]] (CIGS), also called [[CIGS solar cell]]s, a type of second-generation [[thin-film solar cell]].<ref>{{cite journal|title = Scaling up issues of CIGS solar cells | Indium has many [[semiconductor]]-related applications. Some indium compounds, such as [[indium antimonide]] and [[indium phosphide]],<ref>{{cite journal|title = Properties, Preparation, and Device Applications of Indium Phosphide|journal = [[Annual Review of Materials Science]]|volume = 11|pages = 441–484|date = 1981|doi = 10.1146/annurev.ms.11.080181.002301|first = K. J.|last = Bachmann|bibcode = 1981AnRMS..11..441B }}</ref> are [[semiconductor]]s with useful properties: one precursor is usually [[trimethylindium]] (TMI), which is also used as the [[semiconductor]] [[dopant]] in II–VI [[compound semiconductor]]s.<ref name="shenai2004" /> InAs and InSb are used for low-temperature transistors and InP for high-temperature transistors.<ref name="Greenwood247" /> The [[compound semiconductor]]s [[InGaN]] and [[InGaP]] are used in [[light-emitting diode]]s (LEDs) and laser diodes.<ref>{{cite book|isbn=978-0-521-53351-5|title=Light-Emitting Diodes|author=Schubert, E. Fred |date=2003|page=16|publisher=Cambridge University Press}}</ref> Indium is used in [[photovoltaics]] as the semiconductor [[copper indium gallium selenide]] (CIGS), also called [[CIGS solar cell]]s, a type of second-generation [[thin-film solar cell]].<ref>{{cite journal|title = Scaling up issues of CIGS solar cells | ||
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[[File:Indium wire.jpg|thumb|left|Ductile indium wire]] | [[File:Indium wire.jpg|thumb|left|Ductile indium wire]] | ||
Indium wire is used as a [[cryogenic seal|vacuum seal]] and a thermal conductor in [[cryogenics]] and [[ultra-high vacuum|ultra-high-vacuum]] applications, in such manufacturing applications as [[gasket]]s that deform to fill gaps.<ref>{{Cite book|url = https://books.google.com/books?id=tfLWfAx1ZWQC&pg=PA296|page = 296|isbn = 978-0-12-475914-5|editor= Weissler, G. L. |date = 1990|publisher = Acad. Press|location = San Diego|title = Vacuum physics and technology}}</ref> Owing to its great plasticity and adhesion to metals, Indium sheets are sometimes used for cold-soldering in [[Microwave engineering|microwave]] circuits and [[waveguide]] joints, where direct soldering is complicated. Indium is an ingredient in the gallium–indium–tin alloy [[galinstan]], which is liquid at room temperature and replaces [[mercury (element)|mercury]] in some [[thermometer]]s.<ref>{{cite journal|doi=10.1007/s00216-005-0069-7|date=Nov 2005|author=Surmann, P|author2=Zeyat, H| title=Voltammetric analysis using a self-renewable non-mercury electrode| volume=383|issue=6|pages=1009–13| pmid=16228199|journal= Analytical and Bioanalytical Chemistry|s2cid=22732411}}</ref> Other alloys of indium with [[bismuth]], [[cadmium]], [[lead]], and [[tin]], which have higher but still low melting points (between 50 and 100 °C), are used in [[fire sprinkler system]]s and heat regulators.<ref name="Greenwood247" /> | Indium wire is used as a [[cryogenic seal|vacuum seal]] and a thermal conductor in [[cryogenics]] and [[ultra-high vacuum|ultra-high-vacuum]] applications, in such manufacturing applications as [[gasket]]s that deform to fill gaps.<ref>{{Cite book|url = https://books.google.com/books?id=tfLWfAx1ZWQC&pg=PA296|page = 296|isbn = 978-0-12-475914-5|editor= Weissler, G. L. |date = 1990|publisher = Acad. Press|location = San Diego|title = Vacuum physics and technology}}</ref> Owing to its great plasticity and adhesion to metals, Indium sheets are sometimes used for cold-soldering in [[Microwave engineering|microwave]] circuits and [[waveguide]] joints, where direct soldering is complicated. Indium is an ingredient in the gallium–indium–tin alloy [[galinstan]], which is liquid at room temperature and replaces [[mercury (element)|mercury]] in some [[thermometer]]s.<ref>{{cite journal|doi=10.1007/s00216-005-0069-7|date=Nov 2005|author=Surmann, P|author2=Zeyat, H| title=Voltammetric analysis using a self-renewable non-mercury electrode| volume=383|issue=6|pages=1009–13| pmid=16228199|journal= Analytical and Bioanalytical Chemistry|s2cid=22732411}}</ref> Other alloys of indium with [[bismuth]], [[cadmium]], [[lead]], and [[tin]], which have higher but still low melting points (between 50 and 100 °C), are used in [[fire sprinkler system]]s and heat regulators.<ref name="Greenwood247" /> | ||
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| HPhrases = {{H-phrases|302|312|332|315|319|335}} | | HPhrases = {{H-phrases|302|312|332|315|319|335}} | ||
| PPhrases = {{P-phrases|261|280|305+351+338}}<ref>{{cite web | url=https://www.sigmaaldrich.com/catalog/product/aldrich/57083?lang=en®ion=US | title=Indium 57083 | access-date=2018-10-02 | archive-date=2018-10-02 | archive-url=https://web.archive.org/web/20181002172504/https://www.sigmaaldrich.com/catalog/product/aldrich/57083?lang=en®ion=US | url-status=live }}</ref> | | PPhrases = {{P-phrases|261|280|305+351+338}}<ref>{{cite web | url=https://www.sigmaaldrich.com/catalog/product/aldrich/57083?lang=en®ion=US | title=Indium 57083 | access-date=2018-10-02 | archive-date=2018-10-02 | archive-url=https://web.archive.org/web/20181002172504/https://www.sigmaaldrich.com/catalog/product/aldrich/57083?lang=en®ion=US | url-status=live }}</ref> | ||
| NFPA-H = | | NFPA-H = 1 | ||
| NFPA-F = 0 | | NFPA-F = 0 | ||
| NFPA-R = 0 | | NFPA-R = 0 | ||
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}} | }} | ||
Indium has no [[Dietary element|metabolic]] role in any organism. | Indium has no [[Dietary element|metabolic]] role in any organism that has been studied. According to one overview, "[there is] no evidence of any health hazard from industrial use of indium."<ref name=Ullmann>{{cite book |last1=Felix |first1=Noël |title=Ullmann's Encyclopedia of Industrial Chemistry |chapter=Indium and Indium Compounds |date=2000 |doi=10.1002/14356007.a14_157 |isbn=978-3-527-30385-4 }}</ref> | ||
==Notes== | ==Notes== | ||
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* [https://www.organic-chemistry.org/chemicals/reductions/indiumlowvalent.shtm Reducing Agents > Indium low valent] {{Webarchive|url=https://web.archive.org/web/20230709174439/https://www.organic-chemistry.org/chemicals/reductions/indiumlowvalent.shtm |date=2023-07-09 }} | * [https://www.organic-chemistry.org/chemicals/reductions/indiumlowvalent.shtm Reducing Agents > Indium low valent] {{Webarchive|url=https://web.archive.org/web/20230709174439/https://www.organic-chemistry.org/chemicals/reductions/indiumlowvalent.shtm |date=2023-07-09 }} | ||
* [https://www.cdc.gov/niosh/npg/npgd0341.html NIOSH Pocket Guide to Chemical Hazards] {{Webarchive|url=https://web.archive.org/web/20151208163910/http://www.cdc.gov/niosh/npg/npgd0341.html |date=2015-12-08 }} (Centers for Disease Control and Prevention) | * [https://www.cdc.gov/niosh/npg/npgd0341.html NIOSH Pocket Guide to Chemical Hazards] {{Webarchive|url=https://web.archive.org/web/20151208163910/http://www.cdc.gov/niosh/npg/npgd0341.html |date=2015-12-08 }} (Centers for Disease Control and Prevention) | ||
* [[usgs.gov]] (Mineral Commodity Summaries 2025): [https://pubs.usgs.gov/periodicals/mcs2025/mcs2025.pdf#page=90 Indium] | |||
{{Subject bar | {{Subject bar | ||