Editing Tellurium

{{For|the astronomical device|tellurion}}
{{Infobox tellurium}}

'''Tellurium''' is a [[chemical element]]; it has [[Symbol (chemistry)|symbol]] '''Te''' and [[atomic number]] 52. It is a brittle, mildly toxic, rare, silver-white [[metalloid]]. Tellurium is chemically related to [[selenium]] and [[sulfur]], all three of which are [[chalcogen]]s. It is occasionally found in its native form as elemental crystals. Tellurium is far more common in the Universe as a whole than on Earth. Its extreme [[abundance of the chemical elements|rarity]] in the Earth's crust, comparable to that of [[platinum]], is due partly to its formation of [[hydrogen telluride|a volatile hydride]] that caused tellurium to be lost to space as a gas during the [[Nebular hypothesis|hot nebular]] [[formation of Earth]].

[[Telluride mineral|Tellurium-bearing compounds]] were first discovered in 1782 in a gold mine in [[Zlatna|Kleinschlatten]], [[Transylvania]] (now Zlatna, [[Romania]]) by Austrian mineralogist [[Franz-Joseph Müller von Reichenstein]], although it was [[Martin Heinrich Klaproth]] who named the new element in 1798 after the Latin {{lang|la|tellus}} 'earth'. [[Gold telluride]] minerals are the most notable natural gold compounds. However, they are not a commercially significant source of tellurium itself, which is normally extracted as a by-product of [[copper]] and [[lead]] production.

Commercially, the primary use of tellurium is [[CdTe solar panel]]s and [[thermoelectric]] devices. A more traditional application in copper ([[tellurium copper]]) and steel [[alloy]]s, where tellurium improves [[machinability]], also consumes a considerable portion of tellurium production.

Tellurium has no biological function, although fungi can use it in place of sulfur and selenium in [[amino acid]]s such as [[tellurocysteine]] and telluromethionine. In humans, tellurium is partly metabolized into [[dimethyl telluride]], (CH<sub>3</sub>)<sub>2</sub>Te, a gas with a garlic-like odor exhaled in the breath of victims of tellurium exposure or poisoning.

==Characteristics==

===Physical properties===
Tellurium has two [[allotrope]]s, crystalline and amorphous. When [[crystal]]line, tellurium is silvery-white with a metallic luster. The crystals are [[trigonal crystal system|trigonal]] and [[chiral]] ([[space group]] 152 or 154 depending on the chirality), like the gray form of [[selenium]]. It is a brittle and easily pulverized metalloid. Amorphous tellurium is a black-brown powder prepared by precipitating it from a solution of [[tellurous acid]] or [[telluric acid]] (Te(OH)<sub>6</sub>).<ref name="lan" /> Tellurium is a [[semiconductor]] that shows greater electrical conductivity in certain directions depending on [[atom]]ic alignment; the conductivity increases slightly when exposed to light ([[photoconductivity]]).<ref>{{Cite book|chapter-url = https://books.google.com/books?id=Ty5Ymlg_Mh0C&pg=PA89|pages = 89–91|isbn = 978-0-8493-8912-2|chapter = Tellurium|publisher = CRC Press|title = Semiconductor materials|first = Lev Isaakovich|last = Berger|year = 1997|url = https://archive.org/details/semiconductormat0000berg/page/89}}</ref> When molten, tellurium is corrosive to copper, [[iron]], and [[stainless steel]]. Of the [[chalcogen]]s (oxygen-family elements), tellurium has the highest melting and boiling points, at {{convert|722.66|and|1261|K|°C}}, respectively.<ref>[http://www.ptable.com/#Property/State Periodic Table]. ptable.com</ref>

===Chemical properties===
Crystalline tellurium consists of parallel helical chains of Te atoms, with three atoms per turn. This gray material resists oxidation by air and is not volatile.<ref>[[#Greenwood|Greenwood]], p. 752</ref>

===Isotopes===
{{Main|Isotopes of tellurium}}
Naturally occurring tellurium has eight isotopes. Six of those isotopes, <sup>120</sup>Te, <sup>122</sup>Te, <sup>123</sup>Te, <sup>124</sup>Te, <sup>125</sup>Te, and <sup>126</sup>Te, are stable. The other two, <sup>128</sup>Te and <sup>130</sup>Te, are slightly radioactive,<ref name="NUBASE">{{Cite journal| last1 = Audi| first1 = G.|title = The NUBASE Evaluation of Nuclear and Decay Properties| journal = Nuclear Physics A| volume = 729| issue = 1| pages = 3–128|publisher = Atomic Mass Data Center| date = 2003| doi = 10.1016/j.nuclphysa.2003.11.001| bibcode=2003NuPhA.729....3A| last2 = Bersillon| first2 = O.| last3 = Blachot| first3 = J.| last4 = Wapstra| first4 = A. H.| url = http://hal.in2p3.fr/in2p3-00014184}}</ref><ref name="Tellurium 128">{{Cite web|title = WWW Table of Radioactive Isotopes: Tellurium|publisher = Nuclear Science Division, Lawrence Berkeley National Laboratory|date = 2008|url = http://ie.lbl.gov/toi/nuclide.asp?iZA=520128|access-date = 2010-01-16|archive-url = https://web.archive.org/web/20100205101344/http://ie.lbl.gov/toi/nuclide.asp?iZA=520128|archive-date = 2010-02-05|url-status = dead}}</ref><ref>{{cite journal|arxiv=hep-ex/0211015|doi= 10.1103/PhysRevC.67.014323|title= New limits on naturally occurring electron capture of <sup>123</sup>Te|journal= Physical Review C|volume= 67|issue= 1|pages= 014323|year= 2003|last1= Alessandrello|first1= A.|last2= Arnaboldi|first2= C.|last3= Brofferio|first3= C.|last4= Capelli|first4= S.|last5= Cremonesi|first5= O.|last6= Fiorini|first6= E.|last7= Nucciotti|first7= A.|last8= Pavan|first8= M.|last9= Pessina|first9= G.|last10= Pirro|first10= S.|last11= Previtali|first11= E.|last12= Sisti|first12= M.|last13= Vanzini|first13= M.|last14= Zanotti|first14= L.|last15= Giuliani|first15= A.|last16= Pedretti|first16= M.|last17= Bucci|first17= C.|last18= Pobes|first18= C.|bibcode= 2003PhRvC..67a4323A|s2cid= 119523039}}</ref> with extremely long half-lives, including 2.2&nbsp;×&nbsp;10<sup>24</sup> years for <sup>128</sup>Te. This is the longest known half-life among all [[radionuclide]]s<ref>{{Cite web|title=Noble Gas Research |publisher=Laboratory for Space Sciences, Washington University in St. Louis |date=2008 |url=http://presolar.wustl.edu/work/noblegas.html |access-date=2013-01-10 |url-status=dead |archive-url=https://web.archive.org/web/20110928143717/http://presolar.wustl.edu/work/noblegas.html |archive-date=September 28, 2011 }}</ref> and is about 160 [[Orders of magnitude (numbers)#1012|trillion]] (10<sup>12</sup>) times the [[Age of the universe|age of the known universe]].

A further 31 artificial [[radioisotope]]s of tellurium are known, with [[atomic mass]]es ranging from 104 to 142 and with half-lives of 19 days or less. Also, 17 [[nuclear isomer]]s are known, with half-lives up to 154 days. Except for [[beryllium-8]] and beta-delayed alpha emission branches in some lighter [[nuclide]]s, tellurium (<sup>104</sup>Te to <sup>109</sup>Te) is the second lightest element with isotopes known to undergo alpha decay, [[antimony]] being the lightest.<ref name="NUBASE" />

The atomic mass of tellurium ({{val|127.60|u=g·mol<sup>−1</sup>}}) exceeds that of iodine ({{val|126.90|u=g·mol<sup>−1</sup>}}), the next element in the periodic table.<ref name="Emsley">{{Cite book|chapter-url = https://books.google.com/books?id=j-Xu07p3cKwC&pg=PA426|isbn = 978-0-19-850340-8|pages = [https://archive.org/details/naturesbuildingb0000emsl/page/426 426–429]|publisher = Oxford University Press|date = 2003|title = Nature's building blocks: an A-Z guide to the elements|chapter = Tellurium|first = John|last = Emsley|url = https://archive.org/details/naturesbuildingb0000emsl/page/426}}</ref>

===Occurrence===
{{see also|Telluride mineral}}
[[File:Tellurium-89043.jpg|thumb|left|Native tellurium crystal on [[sylvanite]] ([[Vatukoula]], [[Viti Levu]], [[Fiji]]). Picture width 2 mm.]]

With an abundance in the Earth's [[crust (geology)|crust]] comparable to that of platinum (about 1&nbsp;μg/kg), tellurium is one of the rarest stable solid elements.<ref>{{Cite book|date=2002|url=https://books.google.com/books?id=g1Kb-xizc1wC&pg=PA396|page=396|title=A handbook of industrial ecology|first1 = Robert U.|last1 = Ayres|first2= Leslie|last2 = Ayres|publisher=Edward Elgar Publishing|isbn=1-84064-506-7}}</ref> In comparison, even [[thulium]] – the rarest of the stable [[lanthanide]]s – has crystal abundances of 500&nbsp;μg/kg (see [[Abundance of the chemical elements]]).<ref>{{Cite journal|doi=10.1103/RevModPhys.28.53|title=Abundances of the Elements|date=1956|last1=Suess|first1=Hans|last2=Urey|first2=Harold|journal=Reviews of Modern Physics|volume=28|issue=1|pages=53–74|bibcode=1956RvMP...28...53S}}</ref>

The rarity of tellurium in the Earth's crust is not a reflection of its cosmic abundance. Tellurium is more abundant than [[rubidium]] in the cosmos, though rubidium is 10,000 times more abundant in the Earth's crust. The rarity of tellurium on Earth is thought to be caused by conditions during preaccretional sorting in the solar nebula, when the stable form of certain elements, in the absence of [[oxygen]] and [[water]], was controlled by the reductive power of free [[hydrogen]]. Under this scenario, certain elements that form volatile [[hydride]]s, such as tellurium, were severely depleted through the evaporation of these hydrides. Tellurium and selenium are the heavy elements most depleted by this process.<ref name="Chemical" />

Tellurium is sometimes found in its native (i.e., elemental) form, but is more often found as the tellurides of [[gold]] such as [[calaverite]] and [[krennerite]] (two different [[polymorphism (materials science)|polymorph]]s of AuTe<sub>2</sub>), [[petzite]], Ag<sub>3</sub>AuTe<sub>2</sub>, and [[sylvanite]], AgAuTe<sub>4</sub>. The town of [[Telluride, Colorado]], was named in the hope of a strike of gold telluride (which never materialized, though gold metal ore was found). Gold itself is usually found uncombined, but when found as a chemical compound, it is often combined with tellurium.<ref name="CRC"/>

Although tellurium is found with gold more often than in uncombined form, it is found even more often combined as tellurides of more common metals (e.g. [[melonite]], NiTe<sub>2</sub>). Natural [[tellurite]] and [[tellurate]] minerals also occur, formed by the oxidation of tellurides near the Earth's surface. In contrast to selenium, tellurium does not usually replace sulfur in minerals because of the great difference in ion radii. Thus, many common sulfide minerals contain substantial quantities of selenium and only traces of tellurium.<ref>{{Cite book|chapter = Phase Relations in the Selenide Telluride Systems|pages =217–256| isbn = 978-90-5410-723-1|chapter-url =https://books.google.com/books?id=HUWRZecignoC&pg=PA217|publisher = Taylor & Francis|date = 1996|title = Geochemistry, mineralogy and genesis of gold deposits|first = I. Y.|last = Nekrasov}}</ref>

In the gold rush of 1893, miners in [[Kalgoorlie]] discarded a pyritic material as they searched for pure gold, and it was used to fill in potholes and build sidewalks. In 1896, that tailing was discovered to be [[calaverite]], a telluride of gold, and it sparked a second gold rush that included mining the streets.<ref>{{Cite book|title=The Earth: An Intimate History |last=Fortey |first=Richard |author-link=Richard Fortey |date=2004 |publisher=[[Harper Perennial]]<!-- presumably UK but not sure --> |isbn=978-0-00-257011-4 |page=230}}</ref>

In 2023 astronomers detected the creation of tellurium during collision between two neutron stars.<ref>{{Cite news |last=Sample |first=Ian |last2= |first2= |date=25 October 2023 |title=Creation of rare heavy elements witnessed in neutron-star collision |language=en-GB |work=The Guardian |url=https://www.theguardian.com/science/2023/oct/25/creation-of-rare-heavy-elements-witnessed-in-neutron-star-collision |access-date=26 October 2023 |archive-url=https://web.archive.org/web/20231026082650/https://www.theguardian.com/science/2023/oct/25/creation-of-rare-heavy-elements-witnessed-in-neutron-star-collision |archive-date=26 October 2023 |issn=0261-3077}}</ref>

==History==
[[File:Martin Heinrich Klaproth.jpg|thumb|upright|alt=Oval black and white engraving of a man looking left with a scarf and a coat with large buttons. |[[Martin Heinrich Klaproth|Klaproth]] named the new element and credited [[Franz Joseph Müller von Reichenstein|von Reichenstein]] with its discovery]]

Tellurium ([[Latin]] ''tellus'' meaning "earth") was discovered in the 18th century in a gold ore from the mines in [[Zlatna|Kleinschlatten]] (today Zlatna), near today's city of [[Alba Iulia]], Romania. This ore was known as "Faczebajer weißes blättriges Golderz" (white leafy gold ore from Faczebaja, German name of Facebánya, now Fața Băii in [[Alba County]]) or ''antimonalischer Goldkies'' (antimonic gold pyrite), and according to [[Anton von Rupprecht]], was ''Spießglaskönig'' (''argent molybdique''), containing native [[antimony]].<ref>{{cite journal|url =https://books.google.com/books?id=SXI_AAAAcAAJ&pg=PA70|last =Rupprecht, von|first = A.|title = Über den vermeintlichen siebenbürgischen natürlichen Spiessglaskönig|trans-title=On the supposedly native antimony of Transylvania|journal = Physikalische Arbeiten der Einträchtigen Freunde in Wien|volume = 1|issue =1 |date = 1783|pages = 70–74}}</ref> In 1782 [[Franz-Joseph Müller von Reichenstein]], who was then serving as the Austrian chief inspector of mines in Transylvania, concluded that the ore did not contain antimony but was [[bismuth sulfide]].<ref>{{cite journal|url = https://books.google.com/books?id=SXI_AAAAcAAJ&pg=PA57| last = Müller|first = F. J.|title = Über den vermeintlichen natürlichen Spiessglaskönig|journal = Physikalische Arbeiten der Einträchtigen Freunde in Wien|volume = 1|issue =1 |date = 1783|pages = 57–59}}</ref> The following year, he reported that this was erroneous and that the ore contained mostly gold and an unknown metal very similar to antimony. After a thorough investigation that lasted three years and included more than fifty tests, Müller determined the [[specific gravity]] of the mineral and noted that when heated, the new metal gives off a white smoke with a [[radish]]-like odor; that it imparts a red color to [[sulfuric acid]]; and that when this solution is diluted with water, it has a black precipitate. Nevertheless, he was not able to identify this metal and gave it the names ''aurum paradoxum'' (paradoxical gold) and ''metallum problematicum'' (problem metal), because it did not exhibit the properties predicted for antimony.<ref name="Reich">{{Cite journal|last = von Reichenstein|first = F. J. M.|date = 1783|title = Versuche mit dem in der Grube Mariahilf in dem Gebirge Fazebay bey Zalathna vorkommenden vermeinten gediegenen Spiesglaskönig|trans-title=Experiments with supposedly native antimony occurring in the Mariahilf mine in the Fazeby mountains near Zalathna|journal = Physikalische Arbeiten der Einträchtigen Freunde in Wien|issue = 1.Quartal|volume = 1783|pages = 63–69|url=https://books.google.com/books?id=SXI_AAAAcAAJ&pg=PA63}}</ref><ref name="ChiuZ" /><ref name="Weeks" />

In 1789, a Hungarian scientist, [[Pál Kitaibel]], discovered the element independently in an ore from [[Deutsch-Pilsen]] that had been regarded as argentiferous [[molybdenite]], but later he gave the credit to Müller. In 1798, it was named by [[Martin Heinrich Klaproth]], who had earlier isolated it from the mineral [[calaverite]].<ref>Klaproth (1798) [https://books.google.com/books?id=8ws_AAAAcAAJ&pg=PA95 "Ueber die siebenbürgischen Golderze, und das in selbigen enthaltene neue Metall"] (On the Transylvanian gold ore, and the new metal contained in it), ''Chemische Annalen für die Freunde der Naturlehre, Arzneygelahrtheit, Haushaltungskunst und Manufacturen'' (Chemical Annals for the Friends of Science, Medicine, Economics, and Manufacturing), '''1''' : 91–104. From [https://books.google.com/books?id=8ws_AAAAcAAJ&pg=PA100-IA4 page 100:] " ''… ; und welchem ich hiermit den, von der alten Muttererde entlehnten, Namen ''Tellurium'' beylege.''" ( … ; and to which I hereby bestow the name ''tellurium'', derived from the old Mother of the Earth.)
* {{cite journal |last1=Klaproth |title=Analyse chimique de la mine de Tellure de Transylvanie |journal=Mémoires de l'Académie royale des sciences et belles-lettres (Berlin). § Classe de philosophie expérimentale |date=1798 |pages=17–37 |url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015073704093&seq=713 |trans-title=Chemical analysis of tellurium ores from Transylvania |language=French}}</ref><ref name="ChiuZ">{{Cite journal|journal = Chemie in unserer Zeit|volume = 36|issue = 5|pages = 334–337|date = 2002|title = Die spannende Entdeckungsgeschichte des Tellurs (1782–1798) Bedeutung und Komplexität von Elemententdeckungen|first = Ekkehard|last = Diemann|author2 = Müller, Achim|author3 = Barbu, Horia|doi = 10.1002/1521-3781(200210)36:5<334::AID-CIUZ334>3.0.CO;2-1}}</ref><ref name="Weeks">{{Cite journal|journal =Journal of Chemical Education|title = The discovery of the elements. VI. Tellurium and selenium |first = Mary Elvira |author-link=Mary Elvira Weeks|last =Weeks|date = 1932|pages = 474–485|doi =10.1021/ed009p474|volume =9|issue =3|bibcode = 1932JChEd...9..474W }}</ref><ref name="Weeks2">{{Cite journal|doi =10.1021/ed012p403|title =The discovery of tellurium|date =1935|last1 =Weeks|first1 =Mary Elvira|author-link1=Mary Elvira Weeks|journal =Journal of Chemical Education|volume =12|pages =403–408|bibcode = 1935JChEd..12..403W|issue =9 }}</ref>

In the early 1920s, [[Thomas Midgley Jr.]] found tellurium prevented [[engine knocking]] when added to fuel, but ruled it out due to the difficult-to-eradicate smell. Midgley went on to discover and popularize the use of [[tetraethyl lead]].<ref>{{cite book | last=Ramsden | first=Eileen | title=Chemistry extension file | publisher=Nelson Thornes | publication-place=Cheltenham | date=2002 | isbn=0-7487-6254-X | oclc=49239046 | page=34}}</ref>

The 1960s brought an increase in thermoelectric applications for tellurium (as [[bismuth telluride]]), and in [[Free machining steel|free-machining]] [[steel]] alloys, which became the dominant use. These applications were overtaken by the growing importance of CdTe in [[thin-film solar cell]]s in the 2000s.<ref name=usgs2/>

==Production==
Most Te (and Se) is obtained from [[porphyry copper deposit]]s, where it occurs in trace amounts.<ref>{{cite book|chapter=Chapter 7: By-Products of Porphyry Copper and Molybdenum Deposits|first1=D. A.|last1=John|first2=R. D.|last2=Taylor|title=Rare earth and critical elements in ore deposits|year=2016|volume=18|pages=137–164|doi=10.5382/Rev.18.07 |url=https://pubs.er.usgs.gov/publication/70048652|editor=Philip L. Verplanck and Murray W. Hitzman}}</ref> The element is recovered from [[anode]] [[sludge]]s from the electrolytic refining of blister [[copper]]. It is a component of dusts from [[blast furnace]] refining of [[lead]]. Treatment of 1000 tons of copper ore yields approximately {{convert|1|kg|lb|spell=in|abbr=off}} of tellurium.<ref>{{cite book|chapter=Tellurium | title=Mineral Facts and Problems | url=https://books.google.com/books?id=M6RGAQAAIAAJ | page=925 | author = Loebenstein, J. Roger | publisher= U.S. Bureau of Mines | date=1981}}</ref>

The anode sludges contain the [[selenide]]s and tellurides of the [[noble metals]] in compounds with the formula M<sub>2</sub>Se or M<sub>2</sub>Te (M = Cu, Ag, Au). At temperatures of 500&nbsp;°C the anode sludges are roasted with [[sodium carbonate]] under air. The metal ions are reduced to the metals, while the telluride is converted to [[sodium tellurite]].<ref name="wiberg2001" />

{{block indent|M<sub>2</sub>Te + O<sub>2</sub> + Na<sub>2</sub>CO<sub>3</sub> → Na<sub>2</sub>TeO<sub>3</sub> + 2 M + CO<sub>2</sub>}}

[[Tellurite (ion)|Tellurites]] can be leached from the mixture with water and are normally present as hydrotellurites HTeO<sub>3</sub><sup>−</sup> in solution. [[Selenite (ion)|Selenites]] are also formed during this process, but they can be separated by adding [[sulfuric acid]]. The hydrotellurites are converted into the insoluble [[tellurium dioxide]] while the selenites stay in solution.<ref name="wiberg2001" />

{{block indent|{{chem|HTeO|3|-}} + OH<sup>−</sup> + H<sub>2</sub>SO<sub>4</sub> → TeO<sub>2</sub> + {{chem|SO|4|2-}} + 2 H<sub>2</sub>O}}

The metal is produced from the oxide (reduced) either by electrolysis or by reacting the [[tellurium dioxide]] with sulfur dioxide in sulfuric acid.<ref name="wiberg2001" />

{{block indent|TeO<sub>2</sub> + 2 SO<sub>2</sub> + 2H<sub>2</sub>O → Te + 2 {{chem|SO|4|2-}} + 4 H<sup>+</sup>}}

Commercial-grade tellurium is usually marketed as 200-[[Mesh (scale)|mesh]] powder but is also available as slabs, ingots, sticks, or lumps. The year-end price for tellurium in 2000 was [[United States dollar|US$]]30 per kilogram. In recent years, the tellurium price was driven up by increased demand and limited supply, reaching as high as [[United States dollar|US$]]220 per pound in 2006.<ref>{{Cite web|url=http://arizonageology.blogspot.com/2007/05/arizona-tellurium-rush.html|access-date=2009-08-08|date=May 21, 2007|title=An Arizona tellurium rush?|publisher=arizonageology.blogspot.com}}</ref><ref>{{Cite web|url=http://www.resourceinvestor.com/News/2007/4/Pages/Byproducts-Part-I--Is-There-a-Tellurium-Rush-in.aspx|access-date=2009-08-08|date=April 19, 2007|title=Byproducts Part I: Is There a Tellurium Rush in the Making?|publisher=resourceinvestor.com|archive-date=2017-06-25|archive-url=https://web.archive.org/web/20170625134721/http://www.resourceinvestor.com/News/2007/4/Pages/Byproducts-Part-I--Is-There-a-Tellurium-Rush-in.aspx|url-status=dead}}</ref> The average annual price for 99.99%-pure tellurium increased from $38 per kilogram in 2017 to $74 per kilogram in 2018.<ref name=usgs2>Schuyler Anderson, C. (August 2022) [https://pubs.usgs.gov/myb/vol1/2018/myb1-2018-selenium-tellurium.pdf Selenium and Tellurium]. ''2018 Minerals Yearbook''. [[United States Geological Survey]]</ref> Despite the expectation that improved production methods will double production, the [[United States Department of Energy]] (DoE) anticipates a supply shortfall of tellurium by 2025.<ref>{{Cite journal|doi = 10.1016/S0262-4079(11)61452-8|title = 13 elements you can't live without|journal = New Scientist|volume = 210|issue = 2817|page = 39|year = 2011|last1 = Crow|first1 = James Mitchell|bibcode = 2011NewSc.210...36C}}</ref>

In the 2020s, China produced ca. 50% of world's tellurium and was the only country that mined Te as the main target rather than a by-product. This dominance was driven by the rapid expansion of solar cell industry in China. In 2022, the largest Te providers by volume were China (340 tonnes), Russia (80 t), Japan (70 t), Canada (50 t), Uzbekistan (50 t), Sweden (40 t) and the United States (no official data).<ref name=usgs>Flanagan, Daniel M. (2023) [https://pubs.usgs.gov/periodicals/mcs2023/mcs2023-tellurium.pdf Tellurium]. [[United States Geological Survey]]</ref>

==Compounds==
{{Main|Tellurium compounds}}
Tellurium belongs to the [[chalcogen]] (group 16) family of elements on the periodic table, which also includes [[oxygen]], [[sulfur]], [[selenium]] and [[polonium]]: Tellurium and selenium compounds are similar. Tellurium exhibits the oxidation states −2, +2, +4 and +6, with +4 being most common.<ref name="lan">{{Cite book|title = The radiochemistry of tellurium|issue = 3038|series = Nuclear science series|publisher = Subcommittee on Radiochemistry, National Academy of Sciences-National Research Council, U.S.|first = G. W.|last = Leddicotte|date = 1961|page = 5|url = http://library.lanl.gov/cgi-bin/getfile?rc000049.pdf|archive-date = 2021-11-06|access-date = 2010-01-28|archive-url = https://web.archive.org/web/20211106195637/https://library.lanl.gov/cgi-bin/getfile?rc000049.pdf|url-status = dead}}</ref>

===Tellurides===

Reduction of Te metal produces the [[Telluride (chemistry)|tellurides]] and polytellurides, Te<sub>n</sub><sup>2−</sup>. The −2 oxidation state is exhibited in binary compounds with many metals, such as [[zinc telluride]], {{chem|ZnTe}}, produced by heating tellurium with zinc.<ref name="roscoe" /> Decomposition of {{chem|ZnTe}} with [[hydrochloric acid]] yields [[hydrogen telluride]] ({{chem|H|2|Te}}), a highly unstable analogue of the other chalcogen hydrides, [[Water (molecule)|{{chem|H|2|O}}]], [[Hydrogen sulfide|{{chem|H|2|S}}]] and [[Hydrogen selenide|{{chem|H|2|Se}}]]:<ref>{{cite book | last=Singh | first=G. | title=Chemistry of lanthanides and actinides | publisher=Discovery Publishing House | publication-place=New Delhi | date=2007 | isbn=978-81-8356-241-6 | oclc=949703811 | page=279}}</ref>
{{block indent|ZnTe + 2 HCl → {{chem|ZnCl|2}} + {{chem|H|2|Te}}}}

===Halides===
The +2 oxidation state is exhibited by the dihalides, {{chem|TeCl|2}}, {{chem|TeBr|2}} and {{chem|TeI|2}}. The dihalides have not been obtained in pure form,<ref name="sykes1990">{{Cite book|title = Advances in Inorganic Chemistry|volume = 35|first = H. J.|last = Emeleus|editor = A. G. Sykes|publisher = Academic Press|date = 1990|isbn = 0-12-023635-4}}</ref>{{rp|274}} although they are known decomposition products of the tetrahalides in organic solvents, and the derived tetrahalotellurates are well-characterized:

{{block indent|Te + {{chem|X|2}} + 2 {{chem|X|-}} → {{chem|TeX|4|2−}}}}

where X is Cl, Br, or I. These anions are [[square planar molecular geometry|square planar]] in geometry.<ref name="sykes1990" />{{rp|281}} Polynuclear anionic species also exist, such as the dark brown {{chem|Te}}{{su|b=2}}{{chem|I|6|2−}},<ref name="sykes1990" />{{rp|283}} and the black {{chem|Te}}{{su|b=4}}{{chem|I|14|2−}}.<ref name="sykes1990" />{{rp|285}}

With fluorine Te forms the [[mixed-valence]] {{chem|Te|2|F|4}} and [[Tellurium hexafluoride|{{chem|TeF|6}}]]. In the +6 oxidation state, the {{chem|–OTeF|5}} structural group occurs in a number of compounds such as [[Teflic acid|{{chem|HOTeF|5}}]], {{chem|B(OTeF|5|)|3}}, {{chem|Xe(OTeF|5|)|2}}, {{chem|Te(OTeF|5|)|4}} and {{chem|Te(OTeF|5|)|6}}.<ref>{{Cite book|chapter = Preparations and Reactions of Inorganic Main-Group Oxide-Fluorides|first1 = John H.|last1 = Holloway|first2 = David|last2 = Laycock|title = Advances in inorganic chemistry and radiochemistry|volume = 27| series = Serial Publication Series|editor = Harry Julius Emeléus|editor2 = A. G. Sharpe|publisher = Academic Press|date = 1983| isbn = 0-12-023627-3|page = 174}}</ref> The [[square antiprism]]atic anion {{chem|TeF|8|2−}} is also attested.<ref name="wiberg2001">{{Cite book|title = Inorganic chemistry|first1 = Egon|last1 = Wiberg|first2 = Arnold Frederick|last2 = Holleman|editor = Nils Wiberg|publisher = Academic Press|date = 2001|isbn = 0-12-352651-5|page = 588|others = translated by Mary Eagleson}}</ref> The other halogens do not form halides with tellurium in the +6 oxidation state, but only tetrahalides ([[Tellurium tetrachloride|{{chem|TeCl|4}}]], [[Tellurium tetrabromide|{{chem|TeBr|4}}]] and [[Tellurium tetraiodide|{{chem|TeI|4}}]]) in the +4 state, and other lower halides ({{chem|Te|3|Cl|2}}, {{chem|Te|2|Cl|2}}, {{chem|Te|2|Br|2}}, {{chem|Te|2|I}} and two forms of {{chem|TeI}}). In the +4 oxidation state, halotellurate anions are known, such as {{chem|TeCl|6|2−}} and {{chem|Te|2|Cl|10|2−}}. Halotellurium cations are also attested, including {{chem|TeI|3|+}}, found in {{chem|TeI|3|AsF|6}}.<ref>{{Cite book|title = Handbook of chalcogen chemistry: new perspectives in sulfur, selenium and tellurium|url = https://archive.org/details/handbookchalcoge00devi_741|url-access = limited|chapter = Recent developments in binary halogen-chalcogen compounds, polyanions and polycations|first = Zhengtao|last = Xu|editor = Francesco A. Devillanova| publisher = Royal Society of Chemistry|date = 2007|isbn = 978-0-85404-366-8|pages = [https://archive.org/details/handbookchalcoge00devi_741/page/n469 457]–466}}</ref>

===Oxocompounds===
[[File:TeO2powder.jpg|thumb|alt=A sample of pale yellow powder|A sample of tellurium dioxide powder]]
Tellurium monoxide was first reported in 1883 as a black amorphous solid formed by the heat decomposition of {{chem|TeSO|3}} in vacuum, disproportionating into [[tellurium dioxide]], {{chem|TeO|2}} and elemental tellurium upon heating.<ref>{{cite encyclopedia|encyclopedia = Encyclopedia of materials, parts, and finishes|title = Tellurium|first = Mel M.|last = Schwartz|edition = 2nd|publisher = CRC Press|date = 2002|isbn = 1-56676-661-3}}</ref><ref name="divers">{{Cite journal|journal = Journal of the Chemical Society|title = On a new oxide of tellurium|first1 = Edward|last1 = Divers|first2 = M.|last2 = Shimosé|volume = 43|doi = 10.1039/CT8834300319|date = 1883|pages = 319–323|url = https://zenodo.org/record/2170636}}</ref> Since then, however, existence in the solid phase is doubted and in dispute, although it is known as a vapor fragment; the black solid may be merely an equimolar mixture of elemental tellurium and tellurium dioxide.<ref name="dutton">{{cite journal |last1 = Dutton |first1 = W. A. |last2 = Cooper |first2 = W. Charles |title = The Oxides and Oxyacids of Tellurium |journal = Chemical Reviews |volume = 66 |pages = 657–675 |date = 1966 |doi = 10.1021/cr60244a003 |issue = 6}}</ref>

Tellurium dioxide is formed by heating tellurium in air, where it burns with a blue flame.<ref name="roscoe">{{Cite book|title = A treatise on chemistry|volume = 1|first1 = Henry Enfield|last1 = Roscoe|author-link1 = Henry Enfield Roscoe|first2 = Carl|author-link2 = Carl Schorlemmer|publisher = Appleton|date = 1878|pages = 367–368|last2 = Schorlemmer}}</ref> Tellurium trioxide, β-{{chem|TeO|3}}, is obtained by thermal decomposition of {{chem|Te(OH)|6}}. The other two forms of trioxide reported in the literature, the α- and γ- forms, were found not to be true oxides of tellurium in the +6 oxidation state, but a mixture of {{chem|Te|4+}}, {{chem|OH|-}} and {{chem|O|2|-}}.<ref name="wickleder">{{Cite book|title = Handbook of chalcogen chemistry: new perspectives in sulfur, selenium and tellurium|url = https://archive.org/details/handbookchalcoge00devi_741|url-access = limited|chapter = Chalcogen-Oxygen Chemistry|first1 = Mathias S.|last1 = Wickleder|editor = Francesco A. Devillanova|publisher = Royal Society of Chemistry|date = 2007|isbn = 978-0-85404-366-8|pages = [https://archive.org/details/handbookchalcoge00devi_741/page/n366 348]–350}}</ref> Tellurium also exhibits mixed-valence oxides, {{chem|Te|2|O|5}} and {{chem|Te|4|O|9}}.<ref name="wickleder" />

The tellurium oxides and hydrated oxides form a series of acids, including [[tellurous acid]] ({{chem|H|2|TeO|3}}), [[telluric acid|orthotelluric acid]] ({{chem|Te(OH)|6}}) and metatelluric acid ({{chem|(H|2|TeO|4|)|''n''}}).<ref name="dutton" /> The two forms of telluric acid form ''[[tellurate]]'' salts containing the TeO{{su|b=4|p=2–}} and TeO{{su|b=6|p=6−}} anions, respectively. Tellurous acid forms ''[[tellurite]]'' salts containing the anion TeO{{su|b=3|p=2−}}.<ref>[[#Greenwood|Greenwood]], p. 748</ref>

===Zintl cations===
[[File:Zintl ion.jpg|thumb|upright=0.5|A solution of {{chem|Te|4|2+}}]]
When tellurium is treated with concentrated sulfuric acid, the result is a red solution of the [[Zintl ion]], {{chem|Te|4|2+}}.<ref name="molnar2009">{{Cite book
| title = Superacid Chemistry
| url = https://archive.org/details/superacidchemist00olah
| url-access = limited
| author1 = Molnar, Arpad 
| author2 = Olah, George Andrew 
| author3 = Surya Prakash, G. K. 
| author4 = Sommer, Jean 
| edition = 2nd
| publisher = Wiley-Interscience
| date = 2009
| isbn = 978-0-471-59668-4
| pages = [https://archive.org/details/superacidchemist00olah/page/n460 444]–445
}}</ref> The oxidation of tellurium by [[arsenic pentafluoride|{{chem|AsF|5}}]] in liquid [[sulfur dioxide|{{chem|SO|2}}]] produces the same [[square planar molecular geometry|square planar]] cation, in addition to the [[trigonal prism]]atic, yellow-orange {{chem|Te|6|4+}}:<ref name="wiberg2001" />

{{block indent|4 Te + 3 {{chem|AsF|5}} → {{chem|Te|4|2+|(AsF|6|-|)|2}} + {{chem|AsF|3}}}}
{{block indent|6 Te + 6 {{chem|AsF|5}} → {{chem|Te|6|4+|(AsF|6|-|)|4}} + 2 {{chem|AsF|3}}}}

Other tellurium Zintl cations include the polymeric {{chem|Te|7|2+}} and the blue-black {{chem|Te|8|2+}}, consisting of two fused 5-membered tellurium rings. The latter cation is formed by the reaction of tellurium with [[tungsten hexachloride]]:<ref name="wiberg2001" />

{{block indent|8 Te + 2 {{chem|WCl|6}} → {{chem|Te|8|2+|(WCl|6|-|)|2}}}}

Interchalcogen cations also exist, such as {{chem|Te|2|Se|6|2+}} (distorted cubic geometry) and {{chem|Te|2|Se|8|2+}}. These are formed by oxidizing mixtures of tellurium and selenium with {{chem|AsF|5}} or [[antimony pentafluoride|{{chem|SbF|5}}]].<ref name="wiberg2001" />

===Organotellurium compounds===
{{Main|Organotellurium chemistry}}
Tellurium does not readily form analogues of [[Alcohol (chemistry)|alcohol]]s and [[thiol]]s, with the functional group –TeH, that are called [[tellurol]]s. The –TeH functional group is also attributed using the prefix ''tellanyl-''.<ref>{{Cite journal|doi = 10.1070/RC1999v068n11ABEH000544|first1 = I. D.|last1 =Sadekov|first2 = A. V.|last2 =Zakharov|title = Stable tellurols and their metal derivatives|journal =Russian Chemical Reviews|date = 1999|volume =68|issue = 11|pages = 909–923|bibcode = 1999RuCRv..68..909S | s2cid=250864006 }}</ref> Like [[Hydrogen telluride|H<sub>2</sub>Te]], these species are unstable with respect to loss of hydrogen. Telluraethers (R–Te–R) are more stable, as are [[telluroxide]]s.<ref>[[#Greenwood|Greenwood]], p. 787</ref>

===Tritelluride quantum materials===

Recently, physicists and materials scientists have been discovering unusual quantum properties associated with layered compounds composed of tellurium that's combined with certain [[rare-earth element]]s, as well as [[yttrium]] (Y).<ref name=Yumigeta1>{{cite journal |last1=Yumigeta |first1=Kentaro |last2=Qin |first2=Ying |last3=Li |first3=Han |last4=Blei |first4=Mark |last5=Attarde |first5=Yashika |last6=Kopas |first6=Cameron |last7=Tongay |first7=Sefaattin |date=2021 |title=Advances in Rare-Earth Tritelluride Quantum Materials: Structure, Properties, and Synthesis |url=https://www.osti.gov/servlets/purl/1816430 |journal=Advanced Science |volume=8 |issue= 12|pages=2004762 |doi=10.1002/advs.202004762 |pmid=34165898 |pmc=8224454 |osti=1816430 |access-date=12 June 2022}}</ref>

These novel materials have the general formula of ''R'' Te<sub>3</sub>, where "''R'' " represents a rare-earth lanthanide (or Y), with the full family consisting of ''R'' = Y, [[lanthanum]] (La), [[cerium]] (Ce), [[praseodymium]] (Pr), [[neodymium]] (Nd), [[samarium]] (Sm), [[gadolinium]] (Gd), [[terbium]] (Tb), [[dysprosium ]] (Dy), [[holmium]] (Ho), [[erbium]] (Er), and [[thulium]] (Tm). Compounds containing [[promethium]] (Pm), [[europium]] (Eu), [[ytterbium]] (Yb), and [[lutetium]] (Lu) have not yet been observed. These materials have a two-dimensional character within an [[orthorhombic crystal system#Two-dimensional|orthorhombic]] crystal structure, with slabs of ''R'' Te separated by sheets of pure tellurium.<ref name=Yumigeta1/>

It is thought that this 2-D layered structure is what leads to a number of interesting quantum features, such as [[charge-density wave]]s, [[electron mobility|high carrier mobility]], [[superconductivity]] under specific conditions, and other peculiar properties whose natures are only now emerging.<ref name=Yumigeta1/>

For example, in 2022, a small group of physicists at [[Boston College]] in Massachusetts led an international team that used optical methods to demonstrate a novel axial mode of a [[Higgs boson|Higgs-]]like particle in ''R'' Te<sub>3</sub> compounds that incorporate either of two rare-earth elements (''R'' = La, Gd).<ref name=Wang1>{{cite journal |last1=Wang |first1=Yiping |last2=Petrides |first2=Ioannis |last3=McNamara |first3=Grant |last4=Hosen |first4=Md Mofazzel |last5=Lei |first5=Shiming |last6=Wu |first6=Yueh-Chun |last7=Hart |first7=James L. |last8=Lv |first8=Hongyan |last9=Yan |first9=Jun |last10=Xiao |first10=Di |last11=Cha |first11=Judy J.|author11-link=Judy Cha |last12=Narang |first12=Prineha |last13=Schoop |first13=Leslie M. |last14=Burch |first14=Kenneth S. |date=8 June 2022 |title=Axial Higgs mode detected by quantum pathway interference in ''R'' Te<sub>3</sub> |url=https://www.nature.com/articles/s41586-022-04746-6 |journal=Nature |volume= 606|issue= 7916|pages= 896–901|doi=10.1038/s41586-022-04746-6 |pmid=35676485 |arxiv=2112.02454 |bibcode=2022Natur.606..896W |s2cid=244908655 |access-date=12 June 2022}}</ref> This long-hypothesized, axial, Higgs-like particle also shows magnetic properties and may serve as a candidate for [[dark matter]].<ref name=Lea1>{{cite news |last=Lea |first=Robert |date=8 June 2022 |title=Physicists discover never-before seen particle sitting on a tabletop |url=https://www.livescience.com/magnetic-higgs-relative-discovered |work= |location=[[Live Science]] |access-date=12 June 2022}}</ref>

==Applications==
In 2022, the major applications of tellurium were [[thin-film solar cell]]s (40%), [[thermoelectrics]] (30%), metallurgy (15%), and rubber (5%), with the first two applications experiencing a rapid increase owing to the worldwide tendency of reducing dependence on the [[fossil fuel]].<ref name=usgs/><ref name=usgs2/> In metallurgy, tellurium is added to [[iron]], [[stainless steel]], [[copper]], and lead alloys. It improves the machinability of copper without reducing its high electrical conductivity. It increases resistance to vibration and fatigue of lead and stabilizes various carbides and in malleable iron.<ref name=usgs2/>

===Heterogeneous catalysis===
Tellurium oxides are components of commercial oxidation catalysts. Te-containing catalysts are used for the [[ammoxidation]] route to [[acrylonitrile]] (CH<sub>2</sub>=CH–C≡N):<ref name="UllTe">{{Ullmann|doi=10.1002/14356007.a26_177|title=Tellurium and Tellurium Compounds|year=2000|last1=Knockaert|first1=Guy|isbn=3527306730}}</ref>

{{block indent|2&nbsp;CH<sub>3</sub>−CH{{=}}CH<sub>2</sub> + 2&nbsp;NH<sub>3</sub> + 3&nbsp;O<sub>2</sub> → 2&nbsp;CH<sub>2</sub>{{=}}CH–C≡N + 6&nbsp;H<sub>2</sub>O}}

Related catalysts are used in the production of [[tetramethylene glycol]]:
{{block indent|CH<sub>3</sub>CH<sub>2</sub>CH<sub>2</sub>CH<sub>3</sub> + O<sub>2</sub> → HOCH<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>OH}}

===Niche===
[[File:NREL Array.jpg|thumb|alt=Solar panels, angled at about 30 degrees, reflect the blue sky from above a grassy field.|A [[Cadmium telluride|CdTe]] [[photovoltaic array]]]]
*Synthetic rubber vulcanized with tellurium shows mechanical and thermal properties that in some ways are superior to [[sulfur vulcanization|sulfur-vulcanized]] materials.<ref>{{Cite book|chapter-url = https://books.google.com/books?id=vGl4yg2Xg0YC&pg=PA42| isbn = 978-0-412-53950-3|page = 42|chapter = Sulfur and Related Elements|publisher = Springer|date = 1987|title = Rubber Technology|first = Maurice|last = Morton}}</ref><ref name="UllTe" />
* Tellurium compounds are specialized pigments for [[ceramic]]s.<ref name="CRC" />
* Selenides and tellurides greatly increase the optical refraction of glass widely used in [[Optical fiber|glass optical fibers]] for telecommunications.<ref>{{Cite journal|doi =10.1016/S0022-3093(05)80767-7|title =Recent advances and trends in chalcogenide glass fiber technology: a review|date =1992|last1 =Nishii|first1 =J.|last2 =Morimoto|first2 =S.|last3 =Inagawa|first3 =I.|last4 =Iizuka|first4 =R.|last5 =Yamashita|first5 =T.|last6 =Yamagishi|first6 =T.|journal =Journal of Non-Crystalline Solids|volume =140|pages =199–208|bibcode=1992JNCS..140..199N}}</ref><ref>{{Cite book|url =https://books.google.com/books?id=BAEnBr6ncmEC&pg=PA1|isbn = 978-0-8493-0368-5|pages =1–11|title = Tellurite glasses handbook: physical properties and data|publisher = CRC Press|date = 2002|first = Raouf A. H.|last = El-Mallawany}}</ref>
* Mixtures of selenium and tellurium are used with [[barium peroxide]] as an oxidizer in the delay powder of electric [[blasting cap]]s.<ref>{{Cite journal|doi = 10.1021/ie50610a035|title = Correspondence. Representing Delay Powder Data.|date = 1960|last1 = Johnson|first1 = L. B.|journal = Industrial & Engineering Chemistry|volume = 52|pages = 868|issue = 10}}</ref>
* [[Neutron]] bombardment of tellurium is the most common way to produce [[iodine-131]].<ref>[http://www.nordion.com/wp-content/uploads/2014/10/MI_Iodine-131_Solution_Canada.pdf Iodine-131 (n, gamma) Radiochemical Sodium Iodide Solution]. nordion.com</ref> This in turn is used to treat some [[thyroid]] conditions, and as a tracer compound in [[hydraulic fracturing]], among other applications.

=== Semiconductor and electronic ===
[[File:NuSTAR detector.JPG|thumb|A [[Cadmium zinc telluride|(Cd,Zn)Te]] detector from the [[NuSTAR]] NASA X-ray telescope]]
[[File:Swift's instrument Burst Alert Telescope (BAT) the detector plane.jpg|thumb|An array of (Cd,Zn)Te X-ray detectors from the Burst Alert Telescope of the NASA [[Neil Gehrels Swift Observatory]]]]
[[Cadmium telluride]] (CdTe) [[Photovoltaic module|solar panels]] exhibit some of the greatest efficiencies for solar cell electric power generators.<ref>{{Cite journal| doi = 10.1126/science.1189690|title = The Impact of Tellurium Supply on Cadmium Telluride Photovoltaics|date = 2010|last1 = Zweibel|first1 = K.|journal = Science|volume = 328|pages = 699–701|pmid = 20448173|issue = 5979|bibcode = 2010Sci...328..699Z |s2cid = 29231392}}</ref>

In 2018, China installed thin-film solar panels with a total power output of 175 GW, more than any other country in the world; most of those panels were made of CdTe.<ref name=usgs2/> In June 2022, China set goals of generating 25% of energy consumption and installing 1.2 billion kilowatts of capacity for wind and solar power by 2030. This proposal will increase the demand for tellurium and its production worldwide, especially in China, where the annual volumes of Te refining increased from 280 tonnes in 2017 to 340 tonnes in 2022.<ref name=usgs/>

{{chem2|[[Cadmium zinc telluride|(Cd,Zn)Te]]}} is an efficient material for detecting [[X-ray]]s.<ref>{{Cite book|chapter-url = https://books.google.com/books?id=cWj_eunQr7kC&pg=PA87|isbn = 978-0-387-95021-1|chapter = Cadmium zinc telluride detector |pages = 87–88|author = Saha, Gopal B.|date = 2001|publisher = Springer|location = New York|title = Physics and radiobiology of nuclear medicine}}</ref> It is being used in the NASA space-based X-ray telescope [[NuSTAR]].

[[HgCdTe|Mercury cadmium telluride]] is a [[semiconductor]] material that is used in thermal imaging devices.<ref name=usgs2/>

===Organotellurium compounds===
{{main|Organotellurium chemistry}}
Organotellurium compounds are mainly of interest in the research context. Several have been examined such as precursors for [[metalorganic vapor phase epitaxy]] growth of II-VI [[compound semiconductor]]s. These precursor compounds include [[dimethyl telluride]], diethyl telluride, diisopropyl telluride, diallyl telluride, and methyl allyl telluride.<ref>{{Cite book|isbn = 978-0-7923-7206-6|chapter-url = https://books.google.com/books?id=HtgEcjQcgkkC&pg=PA265|chapter = Metalorganic vapour phase epitaxy|pages =265–267|editor=Capper, Peter|editor2=Elliott, C. T.|date = 2001|publisher = Kluwer Academic|location = Boston, Mass.|title = Infrared detectors and emitters : materials and devices}}</ref> Diisopropyl telluride (DIPTe) is the preferred precursor for low-temperature growth of CdHgTe by [[MOVPE]].<ref>{{Cite journal|title = Ultra-pure organotellurium precursors for the low-temperature MOVPE growth of II/VI compound semiconductors|doi = 10.1016/0022-0248(88)90613-6|journal = Journal of Crystal Growth|volume = 93|date = 1988|pages = 744–749|last1 = Shenai-Khatkhate|first1 = Deodatta V.|issue =1–4|bibcode = 1988JCrGr..93..744S|last2 = Webb|first2 = Paul|last3 = Cole-Hamilton|first3 = David J.|last4 = Blackmore|first4 = Graham W.|last5 = Brian Mullin|first5 = J. }}</ref> The greatest purity [[metalorganics]] of both [[selenium]] and tellurium are used in these processes. The compounds for semiconductor industry and are prepared by [[adduct purification]].<ref>{{Cite journal|title = Organometallic Molecules for Semiconductor Fabrication [and Discussion]|first6 = P.|last6 = Day|first5 = D. J.|last5 = Cole-Hamilton|first4 = J. B.|last4 = Mullin|first3 = A. E. D.|last3 = McQueen|doi = 10.1098/rsta.1990.0011|first2 = M. B.|journal = Phil. Trans. R. Soc. Lond. A|volume = 330|last2 = Parker|date = 1990|pages = 173–182|last1 = Shenai-Khatkhate|first1 = Deodatta V.|issue =1610|bibcode = 1990RSPTA.330..173S |s2cid = 100757359}}</ref><ref>Mullin, J.B.; Cole-Hamilton, D.J.; Shenai-Khatkhate, D.V.; Webb P. (May 26, 1992) {{US patent|5117021}} "Method for purification of tellurium and selenium alkyls"</ref>

[[Tellurium suboxide]] is used in the media layer of rewritable [[optical disc]]s, including [[CD-RW|ReWritable Compact Discs]] ([[CD-RW]]), ReWritable Digital Video Discs ([[DVD-RW]]), and ReWritable [[Blu-ray Disc]]s.<ref>{{Cite web|url = https://www.engadget.com/2006/10/19/panasonic-says-that-its-100gb-blu-ray-discs-will-last-a-century/|title = Panasonic says that its 100GB Blu-ray discs will last a century|access-date = 2008-11-13|first = Cyrus|last = Farivar|date =2006-10-19}}</ref><ref>{{Cite journal|journal = Japanese Journal of Applied Physics|volume = 37|issue = 4B|date = 1998|pages = 2163–2167|title = Dual-Layer Optical Disk with Te–O–Pd Phase-Change Film|author = Nishiuchi, Kenichi|author2 = Kitaura, Hideki|author3 = Yamada, Noboru|author4 = Akahira, Nobuo|doi = 10.1143/JJAP.37.2163|bibcode = 1998JaJAP..37.2163N| s2cid=119849468 }}</ref>

Tellurium is used in the [[phase change memory]] chips<ref>{{Cite journal|title = Overview of Phase-Change Chalcogenide Nonvolatile Memory Technology|first =S.|last = Hudgens|author2=Johnson, B. | volume = 29|issue = 11|pages = 829–832|date = 2004|journal = MRS Bulletin|doi = 10.1557/mrs2004.236|s2cid =137902404}}
</ref> developed by [[Intel]].<ref>{{Cite journal| journal = IEEE Spectrum|volume =40|issue = 3|date = 2003|pages = 48–54|doi = 10.1109/MSPEC.2003.1184436|title = The New Indelible Memories|first = Linda|last = Geppert}}</ref> [[Bismuth telluride]] (Bi<sub>2</sub>Te<sub>3</sub>) and [[lead telluride]] are working elements of [[thermoelectric]] devices. [[Lead telluride]] exhibits promise in far-[[infrared]] detectors.<ref name=usgs2/>

=== Photocathodes ===
Tellurium shows up in a number of [[photocathode]]s used in solar blind [[photomultiplier tube]]s<ref>{{Cite journal|last1=Taft|first1=E.|last2=Apker|first2=L.|date=1953-02-01|title=Photoemission from Cesium and Rubidium Tellurides|url=https://www.osapublishing.org/josa/abstract.cfm?uri=josa-43-2-81|journal=JOSA|language=EN|volume=43|issue=2|pages=81–83|doi=10.1364/JOSA.43.000081|bibcode=1953JOSA...43...81T}}</ref> and for high brightness [[photoinjector]]s driving modern particle accelerators. The photocathode Cs-Te, which is predominantly Cs<sub>2</sub>Te, has a photoemission threshold of 3.5 eV and exhibits the uncommon combination of high quantum efficiency (>10%) and high durability in poor vacuum environments (lasting for months under use in RF electron guns).<ref>[[Triveni Rao|Rao, T.]], & Dowell, D. H. (2013). ''An engineering guide to photoinjectors''. CreateSpace Independent Publishing.</ref>  This has made it the go to choice for photoemission electron guns used in driving [[Free-electron laser|free electron lasers]].<ref>LCLS-II Project Team. (2015). [https://portal.slac.stanford.edu/sites/ard_public/people/tora/Temp/150921%20LCLS-II%20FDR.pdf ''LCLS-II Final Design Report'']. (LCLSII-1.1-DR-0251-R0). SLAC.</ref>  In this application, it is usually driven at the wavelength 267&nbsp;nm which is the third harmonic of commonly used [[Ti-sapphire laser]]s. More Te containing photocathodes have been grown using other alkali metals such as rubidium, Potassium, and Sodium, but they have not found the same popularity that Cs-Te has enjoyed.<ref>{{Cite patent|title=Bi-alkali telluride photocathode|gdate=1978-07-20|country=US|number=4196257|pubdate=1980-04-01|assign=[[RCA Corporation]]|inventor1-last=Engstrom |inventor1-first=Ralph W. |inventor2-last=McDonie |inventor2-first=Arthur F.}}</ref><ref>Trautner, H. (2000). ''Spectral Response of Cesium Telluride and Rubidium Telluride Photocathodes for the Production of Highly Charged Electron Bunches''. CERN.</ref>

=== Thermoelectric material ===
Tellurium itself can be used as a high-performance elemental thermoelectric material. A trigonal Te with the space group of P3<sub>1</sub>21 can transfer into a topological insulator phase, which is suitable for thermoelectric material. Though often not considered as a thermoelectric material alone, polycrystalline tellurium does show great thermoelectric performance with the thermoelectric figure of merit, zT, as high as 1.0, which is even higher than some of other conventional TE materials like SiGe and BiSb.<ref>{{Cite journal |last1=Lin |first1=Siqi |last2=Li |first2=Wen |last3=Chen |first3=Zhiwei |last4=Shen |first4=Jiawen |last5=Ge |first5=Binghui |last6=Pei |first6=Yanzhong |date=2016-01-11 |title=Tellurium as a high-performance elemental thermoelectric |journal=Nature Communications |language=en |volume=7 |issue=1 |pages=10287 |doi=10.1038/ncomms10287 |pmid=26751919 |pmc=4729895 |bibcode=2016NatCo...710287L |issn=2041-1723}}</ref>

Telluride, which is a compound form of tellurium, is a more common TE material. Typical and ongoing research includes Bi<sub>2</sub>Te<sub>3</sub>, and La<sub>3−x</sub>Te<sub>4</sub>, etc. Bi<sub>2</sub>Te<sub>3</sub> is widely used from energy conversion to sensing to cooling due to its great TE properties. The BiTe-based TE material can achieve a conversion efficiency of 8%, an average zT value of 1.05 for p-type and 0.84 for n-type bismuth telluride alloys.<ref>{{Cite journal |last1=Nozariasbmarz |first1=Amin |last2=Poudel |first2=Bed |last3=Li |first3=Wenjie |last4=Kang |first4=Han Byul |last5=Zhu |first5=Hangtian |last6=Priya |first6=Shashank |date=2020-07-24 |title=Bismuth Telluride Thermoelectrics with 8% Module Efficiency for Waste Heat Recovery Application |journal=iScience |language=en |volume=23 |issue=7 |pages=101340 |doi=10.1016/j.isci.2020.101340 |pmid=32688286 |pmc=7369584 |bibcode=2020iSci...23j1340N |issn=2589-0042}}</ref> Lanthanum telluride can be potentially used in deep space as a thermoelectric generator due to the huge temperature difference in space. The zT value reaches to a maximum of ~1.0 for a La<sub>3−x</sub>Te<sub>4</sub> system with x near 0.2. This composition also allows other chemical substitution which may enhance the TE performance. The addition of Yb, for example, may increase the zT value from 1.0 to 1.2 at 1275K, which is greater than the current SiGe power system.<ref>{{Cite journal |last1=May |first1=Andrew |last2=Snyder |first2=Jeff |last3=Fleurial |first3=Jean-Pierre |last4=El-Genk |first4=Mohamed S. |date=2008 |title=Lanthanum Telluride: Mechanochemical Synthesis of a Refractory Thermoelectric Material |url=http://aip.scitation.org/doi/abs/10.1063/1.2845029 |journal=AIP Conference Proceedings |language=en |location=Albuquerque (New Mexico) |publisher=AIP |volume=969 |pages=672–678 |doi=10.1063/1.2845029|bibcode=2008AIPC..969..672M }}</ref>

==Biological role==
Tellurium has no known biological function, although fungi can incorporate it in place of sulfur and selenium into amino acids such as [[tellurocysteine]] and [[telluromethionine]].<ref name="tellurium-fungi">{{Cite journal|doi = 10.1007/BF02917437|title = Incorporation of tellurium into amino acids and proteins in a tellurium-tolerant fungi|date = 1989|last1 = Ramadan|first1 = Shadia E.|last2 = Razak|first2 = A. A.|last3 = Ragab|first3 = A. M.|last4 = El-Meleigy|first4 = M.|journal = Biological Trace Element Research|volume = 20|pages = 225–32|pmid = 2484755|issue = 3| bibcode=1989BTER...20..225R |s2cid = 9439946}}</ref><ref>{{cite book|author=Rahman, Atta-ur|title=Studies in Natural Products Chemistry|url=https://books.google.com/books?id=8Ugmrew2EqEC&pg=PA905|date=2008|publisher=Elsevier|isbn=978-0-444-53181-0|pages=905–}}</ref> Organisms have shown a highly variable tolerance to tellurium compounds. Many bacteria, such as ''[[Pseudomonas aeruginosa]]'' and ''[[Gayadomonas]]'' sp, take up tellurite and reduce it to elemental tellurium, which accumulates and causes a characteristic and often dramatic darkening of cells.<ref>{{Cite journal|title=C-di-GMP regulates ''Pseudomonas aeruginosa'' stress response to tellurite during both planktonic and biofilm modes of growth |journal=Scientific Reports |year=2015 |doi=10.1038/srep10052 |pmid=25992876 |pmc=4438720 |volume=5 |pages=10052|bibcode=2015NatSR...510052C |last1=Chua |first1=Song Lin |last2=Sivakumar |first2=Krishnakumar |last3=Rybtke |first3=Morten |last4=Yuan |first4=Mingjun |last5=Andersen |first5=Jens Bo |last6=Nielsen |first6=Thomas E. |last7=Givskov |first7=Michael |last8=Tolker-Nielsen |first8=Tim |last9=Cao |first9=Bin |last10=Kjelleberg |first10=Staffan |last11=Yang |first11=Liang }}</ref><ref>{{Cite journal |last1=Abd El-Ghany |first1=Mohamed N. |last2=Hamdi |first2=Salwa A. |last3=Korany |first3=Shereen M. |last4=Elbaz |first4=Reham M. |last5=Farahat |first5=Mohamed G. |date=2023-02-22 |title=Biosynthesis of Novel Tellurium Nanorods by Gayadomonas sp. TNPM15 Isolated from Mangrove Sediments and Assessment of Their Impact on Spore Germination and Ultrastructure of Phytopathogenic Fungi |journal=Microorganisms |language=en |volume=11 |issue=3 |pages=558 |doi=10.3390/microorganisms11030558 |doi-access=free |issn=2076-2607 |pmc=10053417 |pmid=36985132}}</ref> In yeast, this reduction is mediated by the [[sulfate assimilation pathway]].<ref>{{Cite journal|doi = 10.1128/EC.00078-10|title = Sulfate assimilation mediates tellurite reduction and toxicity in ''Saccharomyces cerevisiae''|first1 = L. G.|last1 = Ottosson|pmid = 20675578|first2 = K.|last2 = Logg|first3 = S.|last3 = Ibstedt|first4 = P.|last4 = Sunnerhagen|first5 = M.|last5 = Käll|first6 = A.|last6 = Blomberg|first7 = J.|last7 = Warringer|journal = Eukaryotic Cell|date = 2010|volume = 9|issue = 10|pages = 1635–47|pmc=2950436}}</ref> Tellurium accumulation seems to account for a major part of the toxicity effects. Many organisms also metabolize tellurium partly to form dimethyl telluride, although dimethyl ditelluride is also formed by some species. Dimethyl telluride has been observed in [[hot spring]]s at very low concentrations.<ref>{{Cite journal|doi = 10.1021/cr010210+|title = Biomethylation of Selenium and Tellurium: Microorganisms and Plants|first1 = Thomas G.|last1 = Chasteen|pmid = 12517179|first2 = Ronald|last2 = Bentley|journal = Chemical Reviews|date = 2003|volume = 103|issue = 1|pages = 1–26}}</ref><ref>{{Cite journal|doi =10.1007/BF02785282|title =Biochemistry of tellurium|date =1996|last1 =Taylor|first1 =Andrew|journal =Biological Trace Element Research|volume =55|pages =231–9|pmid =9096851|issue =3|bibcode =1996BTER...55..231T|s2cid =10691234}}</ref>

[[Tellurite agar]] is used to identify members of the [[corynebacterium]] genus, most typically ''[[Corynebacterium diphtheriae]]'', the pathogen responsible for [[diphtheria]].<ref>{{Cite journal|doi = 10.1017/S0022172400065025|title = Diphtheria in Europe|journal = The Journal of Hygiene|date = 1984|volume = 93|issue = 3|last = Kwantes|first = W.|pages = 433–437|pmid = 6512248|pmc = 2129475|jstor=3862778}}</ref>

==Precautions==
{{Chembox
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|Section7={{Chembox Hazards
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| GHSPictograms = {{GHS06}}{{GHS07}}{{GHS08}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|301|317|319|332|335|360|362|412}}<ref>[https://pubchem.ncbi.nlm.nih.gov/compound/6327182#datasheet=LCSS&section=GHS-Classification Tellurium]. Pubchem. U.S. National Library of Medicine</ref>
| PPhrases = {{P-phrases|201|261|280|308+313}}<ref>{{Cite web|url=https://www.sigmaaldrich.com/catalog/product/aldrich/452378|title=Tellurium 452378|website=Sigma-Aldrich}}</ref>
| NFPA-H = 2
| NFPA-F = 0
| NFPA-R = 0
| NFPA-S = 
| NFPA_ref = 
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Tellurium and tellurium compounds are considered to be mildly [[toxic]] and need to be handled with care, although acute poisoning is rare.<ref name="Harrison">{{Cite web|last1 = Harrison|first1 = W.|first2 = S.|last2 =Bradberry|first3 =J. |last3 = Vale |title = Tellurium |publisher = [[International Programme on Chemical Safety]] |date=1998-01-28 |url = http://www.intox.org/databank/documents/chemical/tellur/ukpid84.htm |access-date = 2007-01-12}}</ref> Tellurium poisoning is particularly difficult to treat as many [[Chelating agents|chelation agents]] used in the treatment of metal poisoning will increase the toxicity of tellurium. Tellurium is not reported to be carcinogenic, but it may be fatal if inhaled, swallowed, or absorbed through skin.<ref name="Harrison" /><ref>{{Cite web |last=Ziemke |first=Tobias |date=2023-09-26 |title=Tellurium Element {{!}} The Thrifty Element Tellurium |url=https://chemistrytalk.org/tellurium-element/ |access-date=2024-05-17 |website=ChemTalk |language=en-US}}</ref>

Humans exposed to as little as 0.01&nbsp;mg/m<sup>3</sup> or less in air exude a foul [[garlic]]-like odor known as "tellurium breath".<ref name="CRC">{{RubberBible97th}}</ref><ref name="Distillations">{{cite journal|last1= Kean |first1=Sam |title=The Scent of a Molecule |journal=Distillations |date=2017|volume=3|issue=3 |page=5 |url=https://www.sciencehistory.org/distillations/magazine/the-scent-of-a-molecule|access-date=May 16, 2018}}</ref>
This is caused by the body converting tellurium from any oxidation state to [[dimethyl telluride]], (CH<sub>3</sub>)<sub>2</sub>Te, a volatile compound with a pungent garlic-like smell. Volunteers given 15&nbsp;mg of tellurium still had this characteristic smell on their breath eight months later. In laboratories, this odor makes it possible to discern which scientists are responsible for tellurium chemistry, and even which books they have handled in the past.<ref>{{Cite web |date=2020-01-16 |title=The periodic table of danger (open access) |url=https://www.ase.org.uk/resources/school-science-review/issue-375/periodic-table-of-danger-open-access |access-date=2024-04-11 |website=www.ase.org.uk}}</ref> Even though the metabolic pathways of tellurium are not known, it is generally assumed that they resemble those of the more extensively studied [[selenium]] because the final methylated metabolic products of the two elements are similar.<ref>{{Cite journal|pmid = 5911055|journal = American Journal of Physiology. Legacy Content|title = Comparative metabolism of selenium and tellurium in sheep and swine|volume = 211|issue = 1|pages = 6–10|author = Wright, PL|author2 = B|date = 1966|doi=10.1152/ajplegacy.1966.211.1.6|doi-access = free}}</ref><ref>{{Cite journal|doi = 10.1007/BF01726117|title = Tellurium-intoxication|date = 1989|last1 = Müller|first1 = R.|last2 = Zschiesche|first2 = W.|last3 = Steffen|first3 = H. M.|last4 = Schaller|first4 = K. H.|journal = Klinische Wochenschrift|volume = 67|pages = 1152–5|pmid = 2586020|issue = 22}}</ref><ref>{{Cite journal|doi = 10.1007/BF02785282|title = Biochemistry of tellurium|first = Andrew|last = Taylor|journal =Biological Trace Element Research|volume = 55|issue = 3|date = 1996|pages =231–239|pmid = 9096851| bibcode=1996BTER...55..231T |s2cid = 10691234}}</ref>

People can be exposed to tellurium in the workplace by inhalation, ingestion, skin contact, and eye contact. The [[Occupational Safety and Health Administration]] (OSHA) limits ([[permissible exposure limit]]) tellurium exposure in the workplace to 0.1&nbsp;mg/m<sup>3</sup> over an eight-hour workday. The [[National Institute for Occupational Safety and Health]] (NIOSH) has set the [[recommended exposure limit]] (REL) at 0.1&nbsp;mg/m<sup>3</sup> over an eight-hour workday. In concentrations of 25&nbsp;mg/m<sup>3</sup>, tellurium is [[IDLH|immediately dangerous to life and health]].<ref>{{Cite web|title = CDC – NIOSH Pocket Guide to Chemical Hazards – Tellurium|url = https://www.cdc.gov/niosh/npg/npgd0587.html|website = www.cdc.gov|access-date = 2015-11-24}}</ref>

==See also==
* The 1862 [[History of the periodic table#Comprehensive formalizations|telluric helix]] of [[Alexandre-Émile Béguyer de Chancourtois]].

==Notes==
{{Notelist}}

==References==
{{Reflist|30em}}

==Cited sources==
*{{cite book|ref=Greenwood|author=Greenwood, N. N.|author2=Earnshaw, A.|name-list-style=amp |date=1997|title=Chemistry of the Elements|edition=2nd|place= Oxford|publisher= Butterworth-Heinemann|isbn=978-0-7506-3365-9}}

==External links==
{{Commons|Tellurium}}
{{Wiktionary|tellurium}}
* [http://minerals.er.usgs.gov/minerals/pubs/commodity/selenium USGS Mineral Information on Selenium and Tellurium]
* [http://www.periodicvideos.com/videos/052.htm Tellurium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
* [https://www.cdc.gov/niosh/npg/npgd0587.html CDC – NIOSH Pocket Guide to Chemical Hazards – Tellurium]
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[[Category:Tellurium| ]]
[[Category:Chemical elements]]
[[Category:Chalcogens]]
[[Category:Metalloids]]
[[Category:Trigonal minerals]]
[[Category:Minerals in space group 152 or 154]]
[[Category:Native element minerals]]
[[Category:Chemical elements with trigonal structure]]
[[Category:Crystals in space group 152 or 154]]