Germanium#Chemistry

File:Mendeleev 1869 prediction of germanium (detail).svg

In his report on The Periodic Law of the Chemical Elements in 1869, the Russian chemist Dmitri Mendeleev predicted the existence of several unknown chemical elements, including one that would fill a gap in the carbon family, located between silicon and tin.{{cite journal |first=Masanori |last=Kaji |title=D. I. Mendeleev's concept of chemical elements and The Principles of Chemistry |journal=Bulletin for the History of Chemistry |volume=27 |issue=1 |pages=4–16 |year=2002 |doi=10.70359/bhc2002v027p004 |url=http://www.scs.uiuc.edu/~mainzv/HIST/awards/OPA%20Papers/2005-Kaji.pdf |access-date=2008-08-20 |archive-url=https://web.archive.org/web/20081217080509/http://www.scs.uiuc.edu/~mainzv/HIST/awards/OPA%20Papers/2005-Kaji.pdf |archive-date=2008-12-17 |url-status=dead}} Because of its position in his periodic table, Mendeleev called it ekasilicon (Es), and he estimated its atomic weight to be 70 (later 72).

In mid-1885, at a mine near Freiberg, Saxony, a new mineral was discovered and named argyrodite because of its high silver content.{{NoteTag|From Greek, argyrodite means silver-containing.{{cite report |url=http://www.handbookofmineralogy.org/pdfs/argyrodite.pdf |publisher=Mineral Data Publishing |title=Argyrodite – {{chem|Ag|8|GeS|6}} |access-date=2008-09-01 |date= |archive-date=2016-03-03 |archive-url=https://web.archive.org/web/20160303221645/http://www.handbookofmineralogy.org/pdfs/argyrodite.pdf |url-status=live}}}} The chemist Clemens Winkler analyzed this new mineral, which proved to be a combination of silver, sulfur, and a new element. Winkler was able to isolate the new element in 1886 and found it similar to antimony. He initially considered the new element to be eka-antimony, but was soon convinced that it was instead eka-silicon.{{cite journal |journal=Berichte der Deutschen Chemischen Gesellschaft |volume=19 |issue=1 |pages=210–211 |title=Germanium, Ge, a New Nonmetal Element |language=de |first=Clemens |last=Winkler |author-link=Clemens Winkler |year=1887 |doi=10.1002/cber.18860190156 |url=http://gallica.bnf.fr/ark%3A/12148/bpt6k90705g/f212.chemindefer |url-status=dead |archive-url=https://web.archive.org/web/20081207033757/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Disc-of-Germanium.html |archive-date=December 7, 2008}} Before Winkler published his results on the new element, he decided that he would name his element neptunium, since the recent discovery of planet Neptune in 1846 had similarly been preceded by mathematical predictions of its existence.{{NoteTag|Just as the existence of the new element had been predicted, the existence of the planet Neptune had been predicted in about 1843 by the two mathematicians John Couch Adams and Urbain Le Verrier, using the calculation methods of celestial mechanics. They did this in attempts to explain the fact that the planet Uranus, upon very close observation, appeared to be being pulled slightly out of position in the sky.{{cite journal |first=J. C. |last=Adams |bibcode=1846MNRAS...7..149A |title=Explanation of the observed irregularities in the motion of Uranus, on the hypothesis of disturbance by a more distant planet |journal=Monthly Notices of the Royal Astronomical Society |volume=7 |issue=9 |pages=149–152 |date=November 13, 1846 |doi=10.1093/mnras/7.9.149 |url=https://zenodo.org/record/1431905 |access-date=August 25, 2019 |archive-date=May 2, 2019 |archive-url=https://web.archive.org/web/20190502014753/https://zenodo.org/record/1431905/files/article.pdf |url-status=live |doi-access=free}} James Challis started searching for it in July 1846, and he sighted this planet on September 23, 1846.{{cite journal |first=Rev. J. |last=Challis |bibcode=1846MNRAS...7..145C |title=Account of observations at the Cambridge observatory for detecting the planet exterior to Uranus |journal=Monthly Notices of the Royal Astronomical Society |volume=7 |issue=9 |pages=145–149 |date=November 13, 1846 |doi=10.1093/mnras/7.9.145 |url=https://zenodo.org/record/1431903 |access-date=August 25, 2019 |archive-date=May 4, 2019 |archive-url=https://web.archive.org/web/20190504065619/https://zenodo.org/record/1431903/files/article.pdf |url-status=live |doi-access=free}}}} However, the name "neptunium" had already been given to another proposed chemical element (though not the element that today bears the name neptunium, which was discovered in 1940).{{NoteTag|R. Hermann published claims in 1877 of his discovery of a new element beneath tantalum in the periodic table, which he named neptunium, after the Greek god of the oceans and seas.{{cite journal |title=Scientific Miscellany |journal=The Galaxy |volume=24 |issue=1 |date=July 1877 |page=131 |isbn=978-0-665-50166-1 |first=Robert |last=Sears |oclc=16890343}}{{cite journal |title=Editor's Scientific Record |journal=Harper's New Monthly Magazine |volume=55 |issue=325 |date=June 1877 |pages=152–153 |url=http://cdl.library.cornell.edu/cgi-bin/moa/moa-cgi?notisid=ABK4014-0055-21 |access-date=2008-09-22 |archive-date=2012-05-26 |archive-url=https://archive.today/20120526215615/http://cdl.library.cornell.edu/cgi-bin/moa/moa-cgi?notisid=ABK4014-0055-21 |url-status=live}} However this metal was later recognized to be an alloy of the elements niobium and tantalum.{{cite web |title=Elementymology & Elements Multidict: Niobium |first=Peter |last=van der Krogt |url=http://elements.vanderkrogt.net/element.php?sym=Nb |access-date=2008-08-20 |archive-date=2010-01-23 |archive-url=https://web.archive.org/web/20100123002753/http://elements.vanderkrogt.net/element.php?sym=Nb |url-status=live}} The name "neptunium" was later given to the synthetic element one step past uranium in the Periodic Table, which was discovered by nuclear physics researchers in 1940.{{cite book |title=Nobel Lectures, Chemistry 1942–1962 |publisher=Elsevier |date=1964 |chapter=The Nobel Prize in Chemistry 1951: presentation speech |first=A. |last=Westgren |chapter-url=http://nobelprize.org/nobel_prizes/chemistry/laureates/1951/press.html |access-date=2008-09-18 |archive-date=2008-12-10 |archive-url=https://web.archive.org/web/20081210174205/http://nobelprize.org/nobel_prizes/chemistry/laureates/1951/press.html |url-status=live}}}} So instead, Winkler named the new element germanium (from the Latin word, Germania, for Germany) in honor of his homeland. Argyrodite proved empirically to be Ag₈GeS₆.

Because this new element showed some similarities with the elements arsenic and antimony, its proper place in the periodic table was under consideration, but its similarities with Dmitri Mendeleev's predicted element "ekasilicon" confirmed that place on the periodic table.{{cite journal |journal=The Manufacturer and Builder |url=http://cdl.library.cornell.edu/cgi-bin/moa/pageviewer?frames=1&coll=moa&view=50&root=%2Fmoa%2Fmanu%2Fmanu0018%2F&tif=00187.TIF |year=1887 |title=Germanium, a New Non-Metallic Element |page=181 |access-date=2008-08-20 |archive-date=2008-12-19 |archive-url=https://web.archive.org/web/20081219162737/http://cdl.library.cornell.edu/cgi-bin/moa/pageviewer?frames=1&coll=moa&view=50&root=%2Fmoa%2Fmanu%2Fmanu0018%2F&tif=00187.TIF |url-status=live}} With further material from 500 kg of ore from the mines in Saxony, Winkler confirmed the chemical properties of the new element in 1887.{{cite journal |first=Clemens |last=Winkler |author-link=Clemens Winkler |journal=J. Prak. Chemie |volume=36 |issue=1 |date=1887 |pages=177–209 |title=Mittheilungen über des Germanium. Zweite Abhandlung |doi=10.1002/prac.18870360119 |url=http://gallica.bnf.fr/ark:/12148/bpt6k90799n/f183.table |access-date=2008-08-20 |language=de |archive-date=2012-11-03 |archive-url=https://web.archive.org/web/20121103012004/http://gallica.bnf.fr/ark:/12148/bpt6k90799n/f183.table |url-status=live}}{{cite journal |first=O. |last=Brunck |title=Obituary: Clemens Winkler |journal=Berichte der Deutschen Chemischen Gesellschaft |volume=39 |issue=4 |year=1886 |pages=4491–4548 |doi=10.1002/cber.190603904164 |url=https://zenodo.org/record/1426200 |language=de |access-date=2020-06-07 |archive-date=2020-08-01 |archive-url=https://web.archive.org/web/20200801004057/https://zenodo.org/record/1426200 |url-status=live}} He also determined an atomic weight of 72.32 by analyzing pure germanium tetrachloride ({{chem|GeCl|4}}), while Lecoq de Boisbaudran deduced 72.3 by a comparison of the lines in the spark spectrum of the element.{{cite journal |title=Sur le poids atomique du germanium |first=M. Lecoq |last=de Boisbaudran |journal=Comptes Rendus |year=1886 |volume=103 |page=452 |url=http://gallica.bnf.fr/ark:/12148/bpt6k3059r/f454.table |access-date=2008-08-20 |language=fr |archive-date=2013-06-20 |archive-url=https://web.archive.org/web/20130620032945/http://gallica.bnf.fr/ark:/12148/bpt6k3059r/f454.table |url-status=live}}

Winkler was able to prepare several new compounds of germanium, including fluorides, chlorides, sulfides, dioxide, and tetraethylgermane (Ge(C₂H₅)₄), the first organogermane. The physical data from those compounds—which corresponded well with Mendeleev's predictions—made the discovery an important confirmation of Mendeleev's idea of element periodicity. Here is a comparison between the prediction and Winkler's data:

Until the late 1930s, germanium was thought to be a poorly conducting metal.{{cite journal |title=Germanium: From Its Discovery to SiGe Devices |author=Haller, E. E. |website=Department of Materials Science and Engineering, University of California, Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley |url=http://www.osti.gov/bridge/servlets/purl/922705-bthJo6/922705.PDF |access-date=2008-08-22 |date=2006-06-14 |archive-date=2019-07-10 |archive-url=https://web.archive.org/web/20190710154435/http://www.osti.gov/bridge/servlets/purl/922705-bthJo6/922705.PDF |url-status=live}} Germanium did not become economically significant until after 1945 when its properties as an electronic semiconductor were recognized. During World War II, small amounts of germanium were used in some special electronic devices, mostly diodes.{{cite news |author=W. K. |url=http://select.nytimes.com/gst/abstract.html?res=F30715FE3F5B157A93C2A8178ED85F478585F9 |newspaper=The New York Times |title=Germanium for Electronic Devices |access-date=2008-08-22 |date=1953-05-10 |archive-date=2013-06-13 |archive-url=https://web.archive.org/web/20130613202934/http://select.nytimes.com/gst/abstract.html?res=F30715FE3F5B157A93C2A8178ED85F478585F9 |url-status=live}}{{cite web |url=http://www.computerhistory.org/semiconductor/timeline/1941-semiconductor.html |title=1941 – Semiconductor diode rectifiers serve in WW II |publisher=Computer History Museum |access-date=2008-08-22 |archive-date=2008-09-24 |archive-url=https://web.archive.org/web/20080924135754/http://www.computerhistory.org/semiconductor/timeline/1941-semiconductor.html |url-status=live}} The first major use was the point-contact Schottky diodes for radar pulse detection during the War. The first silicon–germanium alloys were obtained in 1955.{{cite web |url=http://www.sp.phy.cam.ac.uk/~SiGe/Silicon%20Germanium%20(SiGe)%20History.html |title=SiGe History |publisher=University of Cambridge |access-date=2008-08-22 |url-status=dead |archive-url=https://web.archive.org/web/20080805204801/http://www.sp.phy.cam.ac.uk/~SiGe/Silicon%20Germanium%20%28SiGe%29%20History.html |archive-date=2008-08-05}} Before 1945, only a few hundred kilograms of germanium were produced in smelters each year, but by the end of the 1950s, the annual worldwide production had reached {{convert|40|MT|ST|lk=on|abbr=off}}.{{cite news |url=http://pubs.acs.org/cen/80th/print/germanium.html |year=2003 |title=Germanium |first=Bethany |last=Halford |work=Chemical & Engineering News |publisher=American Chemical Society |access-date=2008-08-22 |archive-date=2008-05-13 |archive-url=https://web.archive.org/web/20080513180858/http://pubs.acs.org/cen/80th/print/germanium.html |url-status=live}}

The development of the germanium transistor in 1948{{cite journal |journal=Physical Review |volume=74 |issue=2 |pages=230–231 |title=The Transistor, A Semi-Conductor Triode |first=J. |last=Bardeen |author2=Brattain, W. H. |year=1948 |doi=10.1103/PhysRev.74.230 |bibcode=1948PhRv...74..230B |doi-access=free}} opened the door to countless applications of solid state electronics.{{cite web |title=Electronics History 4 – Transistors |url=http://www.greatachievements.org/?id=3967 |publisher=National Academy of Engineering |access-date=2008-08-22 |archive-date=2007-10-20 |archive-url=https://web.archive.org/web/20071020030644/http://www.greatachievements.org/?id=3967 |url-status=live}} From 1950 through the early 1970s, this area provided an increasing market for germanium, but then high-purity silicon began replacing germanium in transistors, diodes, and rectifiers.{{cite journal |title=Germanium – Statistics and Information |author=U.S. Geological Survey |year=2008 |journal=U.S. Geological Survey, Mineral Commodity Summaries |url=http://minerals.usgs.gov/minerals/pubs/commodity/germanium/ |quote=Select 2008 |access-date=2008-08-28 |archive-date=2008-09-16 |archive-url=https://web.archive.org/web/20080916115005/http://minerals.usgs.gov/minerals/pubs/commodity/germanium/ |url-status=live}} For example, the company that became Fairchild Semiconductor was founded in 1957 with the express purpose of producing silicon transistors. Silicon has superior electrical properties, but it requires much greater purity that could not be commercially achieved in the early years of semiconductor electronics.{{cite journal |journal=IEEE Transactions on Electron Devices |volume=ED-23 |issue=7 |date=July 1976 |title=Single Crystals of Germanium and Silicon-Basic to the Transistor and Integrated Circuit |first=Gordon K. |last=Teal |pages=621–639 |doi=10.1109/T-ED.1976.18464 |bibcode=1976ITED...23..621T |s2cid=11910543}}

Meanwhile, the demand for germanium for fiber optic communication networks, infrared night vision systems, and polymerization catalysts increased dramatically. These end uses represented 85% of worldwide germanium consumption in 2000. The US government even designated germanium as a strategic and critical material, calling for a 146 ton (132 tonne) supply in the national defense stockpile in 1987.

Germanium differs from silicon in that the supply is limited by the availability of exploitable sources, while the supply of silicon is limited only by production capacity since silicon comes from ordinary sand and quartz. While silicon could be bought in 1998 for less than $10 per kg, the price of germanium was almost $800 per kg.

Under standard conditions, germanium is a brittle, silvery-white, semiconductor. This form constitutes an allotrope known as α-germanium, which has a metallic luster and a diamond cubic crystal structure, the same structure as silicon and diamond. In this form, germanium has a threshold displacement energy of $19.7^\{+0.6\}\_\{-0.5\}~\backslash text\{eV\}$.{{Cite journal |last1=Agnese |first1=R. |last2=Aralis |first2=T. |last3=Aramaki |first3=T. |last4=Arnquist |first4=I. J. |last5=Azadbakht |first5=E. |last6=Baker |first6=W. |last7=Banik |first7=S. |last8=Barker |first8=D. |last9=Bauer |first9=D. A. |date=2018-08-27 |title=Energy loss due to defect formation from 206Pb recoils in SuperCDMS germanium detectors |journal=Applied Physics Letters |volume=113 |issue=9 |pages=092101 |doi=10.1063/1.5041457 |issn=0003-6951 |arxiv=1805.09942 |bibcode=2018ApPhL.113i2101A |s2cid=118627298}} At pressures above 120 kbar, germanium becomes the metallic allotrope β-germanium with the same structure as β-tin. Like silicon, gallium, bismuth, antimony, and water, germanium is one of the few substances that expands as it solidifies (i.e. freezes) from the molten state.

Germanium is a semiconductor having an indirect bandgap, as is crystalline silicon. Zone refining techniques have led to the production of crystalline germanium for semiconductors that has an impurity of only one part in 10¹⁰,{{cite web |publisher=Los Alamos National Laboratory |title=Germanium |url=http://periodic.lanl.gov/32.shtml |access-date=2008-08-28 |archive-date=2011-06-22 |archive-url=https://web.archive.org/web/20110622065850/http://periodic.lanl.gov/32.shtml |url-status=live}}

making it one of the purest materials ever obtained.

{{cite book |title=The Primordial Universe: 28 June – 23 July 1999 |editor=Binetruy, B |chapter=Dark Matter: Direct Detection |author=Chardin, B. |publisher=Springer |date=2001 |isbn=978-3-540-41046-1 |page=308}}

The first semi-metallic material discovered (in 2005) to become a superconductor in the presence of an extremely strong electromagnetic field was an alloy of germanium, uranium, and rhodium.

{{cite journal |title=Magnetic field-induced superconductivity in the ferromagnet URhGe |last1=Lévy |first1=F. |last2=Sheikin |first2=I. |last3=Grenier |first3=B. |last4=Huxley |first4=A. |journal=Science |date=August 2005 |volume=309 |issue=5739 |pages=1343–1346 |pmid=16123293 |bibcode=2005Sci...309.1343L |doi=10.1126/science.1115498 |s2cid=38460998}}

Pure germanium is known to spontaneously extrude very long screw dislocations, referred to as germanium whiskers. The growth of these whiskers is one of the primary reasons for the failure of older diodes and transistors made from germanium, as, depending on what they eventually touch, they may lead to an electrical short.{{cite journal |title=Morphology of Germanium Whiskers |first=E. I. |last=Givargizov |journal=Kristall und Technik |volume=7 |issue=1–3 |doi=10.1002/crat.19720070107 |pages=37–41 |year=1972|bibcode=1972CryRT...7...37G }}

{{Main|Germanium compounds}}

Elemental germanium starts to oxidize slowly in air at around 250 °C, forming GeO₂ .{{cite journal |doi=10.1016/S0169-4332(98)00251-7 |title=KRXPS study of the oxidation of Ge(001) surface |date=1998 |author=Tabet, N |journal=Applied Surface Science |volume=134 |issue=1–4 |pages=275–282 |bibcode=1998ApSS..134..275T |last2=Salim |first2=Mushtaq A.}} Germanium is insoluble in dilute acids and alkalis but dissolves slowly in hot concentrated sulfuric and nitric acids and reacts violently with molten alkalis to produce germanates ({{chem|[GeO|3|]|2−}}). Germanium occurs mostly in the oxidation state +4 although many +2 compounds are known.{{Greenwood&Earnshaw}} Other oxidation states are rare: +3 is found in compounds such as Ge₂Cl₆, and +3 and +1 are found on the surface of oxides,{{cite journal |doi=10.1016/S0368-2048(98)00451-4 |title=XPS study of the growth kinetics of thin films obtained by thermal oxidation of germanium substrates |first3=A. L. |last3=Al-Oteibi |first2=M. A. |date=1999 |last2=Salim |author=Tabet, N |journal=Journal of Electron Spectroscopy and Related Phenomena |volume=101–103 |pages=233–238 |bibcode=1999JESRP.101..233T}} or negative oxidation states in germanides, such as −4 in {{chem|Mg|2|Ge}}. Germanium cluster anions (Zintl ions) such as Ge₄²⁻, Ge₉⁴⁻, Ge₉²⁻, [(Ge₉)₂]⁶⁻ have been prepared by the extraction from alloys containing alkali metals and germanium in liquid ammonia in the presence of ethylenediamine or a cryptand.{{cite journal |title=Oxidative Coupling of Deltahedral [Ge₉]⁴⁻ Zintl Ions |first1=Li |last1=Xu |last2=Sevov |first2=Slavi C. |journal=J. Am. Chem. Soc. |date=1999 |volume=121 |issue=39 |pages=9245–9246 |doi=10.1021/ja992269s|bibcode=1999JAChS.121.9245X }} The oxidation states of the element in these ions are not integers—similar to the ozonides O₃⁻.

Two oxides of germanium are known: germanium dioxide ({{chem|GeO|2}}, germania) and germanium monoxide, ({{chem|GeO}}).{{cite book |last=Holleman |first=A. F. |author2=Wiberg, E. |author3=Wiberg, N. |title=Lehrbuch der Anorganischen Chemie |edition=102nd |publisher=de Gruyter |date=2007 |isbn=978-3-11-017770-1 |oclc=145623740}} The dioxide, GeO₂, can be obtained by roasting germanium disulfide ({{chem|GeS|2}}), and is a white powder that is only slightly soluble in water but reacts with alkalis to form germanates. The monoxide, germanous oxide, can be obtained by the high temperature reaction of GeO₂ with elemental Ge. The dioxide (and the related oxides and germanates) exhibits the unusual property of having a high refractive index for visible light, but transparency to infrared light.{{cite journal |doi=10.1111/j.1151-2916.2002.tb00594.x |title=Infrared Transparent Germanate Glass-Ceramics |first=Shyam S. |last=Bayya |author2=Sanghera, Jasbinder S. |author3=Aggarwal, Ishwar D. |author4=Wojcik, Joshua A. |journal=Journal of the American Ceramic Society |volume=85 |issue=12 |pages=3114–3116 |date=2002}}{{cite journal |doi=10.1007/BF00614256 |title=Infrared reflectance and transmission spectra of germanium dioxide and its hydrolysis products |date=1975 |last1=Drugoveiko |first1=O. P. |journal=Journal of Applied Spectroscopy |volume=22 |issue=2 |pages=191–193 |last2=Evstrop'ev |first2=K. K. |last3=Kondrat'eva |first3=B. S. |last4=Petrov |first4=Yu. A. |last5=Shevyakov |first5=A. M. |bibcode=1975JApSp..22..191D |s2cid=97581394}} Bismuth germanate, Bi₄Ge₃O₁₂ (BGO), is used as a scintillator.{{cite journal |title=A Bismuth Germanate-Avalanche Photodiode Module Designed for Use in High Resolution Positron Emission Tomography |last=Lightstone |first=A. W. |author2=McIntyre, R. J. |author3=Lecomte, R. |author4=Schmitt, D. |journal=IEEE Transactions on Nuclear Science |date=1986 |volume=33 |issue=1 |pages=456–459 |doi=10.1109/TNS.1986.4337142 |bibcode=1986ITNS...33..456L |s2cid=682173}}

Binary compounds with other chalcogens are also known, such as the disulfide ({{chem|GeS|2}}) and diselenide ({{chem|GeSe|2}}), and the monosulfide (GeS), monoselenide (GeSe), and monotelluride (GeTe). GeS₂ forms as a white precipitate when hydrogen sulfide is passed through strongly acid solutions containing Ge(IV). The disulfide is appreciably soluble in water and in solutions of caustic alkalis or alkaline sulfides. Nevertheless, it is not soluble in acidic water, which allowed Winkler to discover the element.{{cite journal |first=Otto H. |last=Johnson |title=Germanium and its Inorganic Compounds |journal=Chem. Rev. |date=1952 |volume=51 |issue=3 |pages=431–469 |doi=10.1021/cr60160a002}} By heating the disulfide in a current of hydrogen, the monosulfide (GeS) is formed, which sublimes in thin plates of a dark color and metallic luster, and is soluble in solutions of the caustic alkalis. Upon melting with alkaline carbonates and sulfur, germanium compounds form salts known as thiogermanates.{{cite journal |doi=10.1039/a703634e |title=First synthesis of mesostructured thiogermanates |date=1997 |last1=Fröba |first1=Michael |journal=Chemical Communications |issue=18 |pages=1729–1730 |last2=Oberender |first2=Nadine}}

File:Germane-2D-dimensions.svg.|alt=Skeletal chemical structure of a tetrahedral molecule with germanium atom in its center bonded to four hydrogen atoms. The Ge–H distance is 152.51 picometers.]]

Four tetrahalides are known. Under normal conditions germanium tetraiodide (GeI₄) is a solid, germanium tetrafluoride (GeF₄) a gas and the others volatile liquids. For example, germanium tetrachloride, GeCl₄, is obtained as a colorless fuming liquid boiling at 83.1 °C by heating the metal with chlorine. All the tetrahalides are readily hydrolyzed to hydrated germanium dioxide. GeCl₄ is used in the production of organogermanium compounds. All four dihalides are known and in contrast to the tetrahalides are polymeric solids. Additionally Ge₂Cl₆ and some higher compounds of formula Ge_nCl_2n+2 are known. The unusual compound Ge₆Cl₁₆ has been prepared that contains the Ge₅Cl₁₂ unit with a neopentane structure.{{cite journal |title=The Crystal Structure and Raman Spectrum of Ge₅Cl₁₂·GeCl₄ and the Vibrational Spectrum of Ge₂Cl₆ |last1=Beattie |first1=I. R. |last2=Jones |first2=P.J. |last3=Reid |first3=G. |author4=Webster, M. |journal=Inorg. Chem. |volume=37 |issue=23 |pages=6032–6034 |date=1998 |doi=10.1021/ic9807341 |pmid=11670739}}

Germane (GeH₄) is a compound similar in structure to methane. Polygermanes—compounds that are similar to alkanes—with formula Ge_nH_2n+2 containing up to five germanium atoms are known. The germanes are less volatile and less reactive than their corresponding silicon analogues. GeH₄ reacts with alkali metals in liquid ammonia to form white crystalline MGeH₃ which contain the GeH₃⁻ anion. The germanium hydrohalides with one, two and three halogen atoms are colorless reactive liquids.

File:NucleophilicAdditionWithOrganogermanium.png addition with an organogermanium compound|alt=Skeletal chemical structures outlining an additive chemical reaction including an organogermanium compound.]]

The first organogermanium compound was synthesized by Winkler in 1887; the reaction of germanium tetrachloride with diethylzinc yielded tetraethylgermane ({{chem|Ge(C|2|H|5|)|4}}). Organogermanes of the type R₄Ge (where R is an alkyl) such as tetramethylgermane ({{chem|Ge(CH|3|)|4}}) and tetraethylgermane are accessed through the cheapest available germanium precursor germanium tetrachloride and alkyl nucleophiles. Organic germanium hydrides such as isobutylgermane ({{chem|(CH|3|)|2|CHCH|2|GeH|3}}) were found to be less hazardous and may be used as a liquid substitute for toxic germane gas in semiconductor applications. Many germanium reactive intermediates are known: germyl free radicals, germylenes (similar to carbenes), and germynes (similar to carbynes).{{cite journal |title=Reactive intermediates in organogermanium chemistry |first=Jacques |last=Satge |journal=Pure Appl. Chem. |volume=56 |issue=1 |pages=137–150 |date=1984 |doi=10.1351/pac198456010137 |s2cid=96576323 |doi-access=free}}{{cite journal |title=Organogermanium Chemistry |first=Denis |last=Quane |author2=Bottei, Rudolph S. |journal=Chemical Reviews |volume=63 |issue=4 |pages=403–442 |date=1963 |doi=10.1021/cr60224a004}} The organogermanium compound 2-carboxyethylgermasesquioxane was first reported in the 1970s, and for a while was used as a dietary supplement and thought to possibly have anti-tumor qualities.

Using a ligand called Eind (1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl) germanium is able to form a double bond with oxygen (germanone). Germanium hydride and germanium tetrahydride are very flammable and even explosive when mixed with air.{{cite news |last=Broadwith |first=Phillip |title=Germanium-oxygen double bond takes centre stage |url=http://www.rsc.org/chemistryworld/News/2012/March/germanone-germanium-oxygen-double-bond-created.asp |access-date=2014-05-15 |newspaper=Chemistry World |date=25 March 2012 |archive-date=2014-05-17 |archive-url=https://web.archive.org/web/20140517121351/http://www.rsc.org/chemistryworld/News/2012/March/germanone-germanium-oxygen-double-bond-created.asp |url-status=live}}

{{main|Isotopes of germanium}}

Germanium occurs in five natural isotopes: {{SimpleNuclide|Germanium|70}}, {{SimpleNuclide|Germanium|72}}, {{SimpleNuclide|Germanium|73}}, {{SimpleNuclide|Germanium|74}}, and {{SimpleNuclide|Germanium|76}}. Of these, {{SimpleNuclide|Germanium|76}} is very slightly radioactive, decaying by double beta decay with a half-life of {{val|1.78|e=21|u=years}}. {{SimpleNuclide|Germanium|74}} is the most common isotope, having a natural abundance of approximately 36%. {{SimpleNuclide|Germanium|76}} is the least common with a natural abundance of approximately 7%.{{NUBASE 2003}} When bombarded with alpha particles, the isotope {{SimpleNuclide|Germanium|72}} will generate stable {{SimpleNuclide|Selenium|77|link=yes}}, releasing high energy electrons in the process. Because of this, it is used in combination with radon for nuclear batteries.Perreault, Bruce A. [https://patents.google.com/patent/US7800286 "Alpha Fusion Electrical Energy Valve"], US Patent 7800286, issued September 21, 2010. {{webarchive |url=https://web.archive.org/web/20071012103442/http://www.nuenergy.org/disclosures/AlphaFusionPatent_05-04-2007.pdf |archive-url=https://web.archive.org/web/20071012103442/http://www.nuenergy.org/disclosures/AlphaFusionPatent_05-04-2007.pdf |archive-date=2007-10-12 |url-status=live |date=October 12, 2007 |title=PDF copy }}

At least 27 radioisotopes have also been synthesized, ranging in atomic mass from 58 to 89. The most stable of these is {{SimpleNuclide|Germanium|68}}, decaying by electron capture with a half-life of {{val|270.95|u=days}}ays. The least stable is {{SimpleNuclide|Germanium|60}}, with a half-life of {{val|30|ul=ms}}. While most of germanium's radioisotopes decay by beta decay, {{SimpleNuclide|Germanium|61}} and {{SimpleNuclide|Germanium|64}} decay by Positron emission delayed proton emission. {{SimpleNuclide|Germanium|84}} through {{SimpleNuclide|Germanium|87}} isotopes also exhibit minor Beta decay delayed neutron emission decay paths.

{{category see also|Germanium minerals}}

File:Renierit.JPG|alt=A brown block of irregular shape and surface, about 6 cm in size.]]

Germanium is created by stellar nucleosynthesis, mostly by the s-process in asymptotic giant branch stars. The s-process is a slow neutron capture of lighter elements inside pulsating red giant stars.{{cite journal |journal=The Astrophysical Journal Letters |volume=578 |issue=1 |pages=L55–L58 |doi=10.1086/344473 |title=Discovery of Enhanced Germanium Abundances in Planetary Nebulae with the Far Ultraviolet Spectroscopic Explorer |first=N. C. |last=Sterling |author2=Dinerstein, Harriet L. |author3=Bowers, Charles W. |bibcode=2002ApJ...578L..55S |arxiv=astro-ph/0208516 |year=2002 |s2cid=119395123 |author2-link=Harriet Dinerstein}} Germanium has been detected in some of the most distant stars{{cite journal |journal=Nature |volume=423 |issue=29 |date=2003-05-01 |pmid=12721614 |doi=10.1038/423029a |title=Astronomy: Elements of surprise |last=Cowan |first=John |page=29 |bibcode=2003Natur.423...29C |s2cid=4330398 |doi-access=free}} and in the atmosphere of Jupiter.{{cite journal |title=The tropospheric gas composition of Jupiter's north equatorial belt /NH₃, PH₃, CH₃D, GeH₄, H₂O/ and the Jovian D/H isotopic ratio |last=Kunde |first=V. |author2=Hanel, R. |author3=Maguire, W. |author4=Gautier, D. |author5=Baluteau, J. P. |author6=Marten, A. |author7=Chedin, A. |author8=Husson, N. |author9=Scott, N. |journal=Astrophysical Journal |volume=263 |date=1982 |pages=443–467 |doi=10.1086/160516 |bibcode=1982ApJ...263..443K}}

Germanium's abundance in the Earth's crust is approximately 1.6 ppm.{{cite journal |doi=10.1016/j.oregeorev.2005.07.034 |title=Metallogenesis of germanium – A review |first=R. |last=Höll |author2=Kling, M. |author3=Schroll, E. |journal=Ore Geology Reviews |volume=30 |issue=3–4 |date=2007 |pages=145–180}} Only a few minerals like argyrodite, briartite, germanite, renierite and sphalerite contain appreciable amounts of germanium.{{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=2017-06-10 |last1=Frenzel |first1=Max |year=2016 |publisher=Unpublished |archive-date=2018-10-06 |archive-url=https://web.archive.org/web/20181006235214/https://www.researchgate.net/publication/309583931 |url-status=live}} Only few of them (especially germanite) are, very rarely, found in mineable amounts.{{cite journal |url=https://www.researchgate.net/publication/250273740 |title=Eyselite, Fe3+Ge34+O7(OH), a new mineral species from Tsumeb, Namibia |journal=The Canadian Mineralogist |volume=42 |issue=6 |pages=1771–1776 |date=December 2004 |doi=10.2113/gscanmin.42.6.1771 |first1=Andrew C. |last1=Roberts |bibcode=2004CaMin..42.1771R |display-authors=etal}}{{Cite web |url=https://www.deutsche-rohstoffagentur.de/DERA/DE/Downloads/vortrag_germanium.pdf?__blob=publicationFile&v=2 |title=Archived copy |access-date=2018-10-06 |archive-date=2018-10-06 |archive-url=https://web.archive.org/web/20181006234914/https://www.deutsche-rohstoffagentur.de/DERA/DE/Downloads/vortrag_germanium.pdf?__blob=publicationFile&v=2 |url-status=live}}{{Cite web |url=http://tupa.gtk.fi/raportti/arkisto/070_peh_76.pdf |title=Archived copy |access-date=2018-10-06 |archive-date=2020-03-20 |archive-url=https://web.archive.org/web/20200320190457/http://tupa.gtk.fi/raportti/arkisto/070_peh_76.pdf |url-status=live}} Some zinc–copper–lead ore bodies contain enough germanium to justify extraction from the final ore concentrate. An unusual natural enrichment process causes a high content of germanium in some coal seams, discovered by Victor Moritz Goldschmidt during a broad survey for germanium deposits.{{cite journal |journal=Nachrichten von der Gesellschaft der Wissenschaften zu Göttingen, Mathematisch-Physikalische Klasse |title=Ueber das Vorkommen des Germaniums in Steinkohlen und Steinkohlenprodukten |last=Goldschmidt |first=V. M. |pages=141–167 |date=1930 |url=http://resolver.sub.uni-goettingen.de/purl?GDZPPN002508303 |access-date=2008-08-25 |archive-date=2018-03-03 |archive-url=https://web.archive.org/web/20180303165042/http://resolver.sub.uni-goettingen.de/purl?GDZPPN002508303 |url-status=live}}{{cite journal |journal=Nachrichten von der Gesellschaft der Wissenschaften zu Göttingen, Mathematisch-Physikalische Klasse |title=Zur Geochemie des Germaniums |last=Goldschmidt |first=V. M. |author2=Peters, Cl. |pages=141–167 |url=http://resolver.sub.uni-goettingen.de/purl?GDZPPN002509180 |date=1933 |access-date=2008-08-25 |archive-date=2008-12-01 |archive-url=https://web.archive.org/web/20081201115130/http://resolver.sub.uni-goettingen.de/purl/?GDZPPN002509180 |url-status=live}} The highest concentration ever found was in Hartley coal ash with as much as 1.6% germanium. The coal deposits near Xilinhaote, Inner Mongolia, contain an estimated 1600 tonnes of germanium.

About 118 tonnes of germanium were produced in 2011 worldwide, mostly in China (80 t), Russia (5 t) and United States (3 t). Germanium is recovered as a by-product from sphalerite zinc ores where it is concentrated in amounts as great as 0.3%,{{cite journal |doi=10.1016/0016-7037(85)90241-8 |title=Germanium geochemistry and mineralogy |date=1985 |last=Bernstein |first=L. |journal=Geochimica et Cosmochimica Acta |volume=49 |issue=11 |pages=2409–2422 |bibcode=1985GeCoA..49.2409B}} especially from low-temperature sediment-hosted, massive Zn–Pb–Cu(–Ba) deposits and carbonate-hosted Zn–Pb deposits.{{Cite journal |title=Gallium, germanium, indium and other minor and trace elements in sphalerite as a function of deposit type – A meta-analysis |last1=Frenzel |first1=Max |date=July 2016 |journal=Ore Geology Reviews |doi=10.1016/j.oregeorev.2015.12.017 |last2=Hirsch |first2=Tamino |last3=Gutzmer |first3=Jens |volume=76 |pages=52–78 |bibcode=2016OGRv...76...52F}} A recent study found that at least 10,000 t of extractable germanium is contained in known zinc reserves, particularly those hosted by Mississippi-Valley type deposits, while at least 112,000 t will be found in coal reserves.{{multiref|{{Cite journal |title=On the geological availability of germanium |journal=Mineralium Deposita |date=2013-12-29 |issn=0026-4598 |pages=471–486 |volume=49 |issue=4 |doi=10.1007/s00126-013-0506-z |first1=Max |last1=Frenzel |first2=Marina P. |last2=Ketris |first3=Jens |last3=Gutzmer |bibcode=2014MinDe..49..471F |s2cid=129902592}}|{{Cite journal |title=Erratum to: On the geological availability of germanium |journal=Mineralium Deposita |date=2014-01-19 |issn=0026-4598 |page=487 |volume=49 |issue=4 |doi=10.1007/s00126-014-0509-4 |first1=Max |last1=Frenzel |first2=Marina P. |last2=Ketris |first3=Jens |last3=Gutzmer |bibcode=2014MinDe..49..487F |s2cid=140620827 |doi-access=free}}}} In 2007 35% of the demand was met by recycled germanium.

While it is produced mainly from sphalerite, it is also found in silver, lead, and copper ores. Another source of germanium is fly ash of power plants fueled from coal deposits that contain germanium. Russia and China used this as a source for germanium.{{cite journal |first=A. V. |last=Naumov |title=World market of germanium and its prospects |journal=Russian Journal of Non-Ferrous Metals |volume=48 |issue=4 |date=2007 |doi=10.3103/S1067821207040049 |pages=265–272 |s2cid=137187498}} Russia's deposits are located in the far east of Sakhalin Island, and northeast of Vladivostok. The deposits in China are located mainly in the lignite mines near Lincang, Yunnan; coal is also mined near Xilinhaote, Inner Mongolia.

The ore concentrates are mostly sulfidic; they are converted to the oxides by heating under air in a process known as roasting:

: GeS₂ + 3 O₂ → GeO₂ + 2 SO₂

Some of the germanium is left in the dust produced, while the rest is converted to germanates, which are then leached (together with zinc) from the cinder by sulfuric acid. After neutralization, only the zinc stays in solution while germanium and other metals precipitate. After removing some of the zinc in the precipitate by the Waelz process, the residing Waelz oxide is leached a second time. The dioxide is obtained as precipitate and converted with chlorine gas or hydrochloric acid to germanium tetrachloride, which has a low boiling point and can be isolated by distillation:

: GeO₂ + 4 HCl → GeCl₄ + 2 H₂O

: GeO₂ + 2 Cl₂ → GeCl₄ + O₂

Germanium tetrachloride is either hydrolyzed to the oxide (GeO₂) or purified by fractional distillation and then hydrolyzed. The highly pure GeO₂ is now suitable for the production of germanium glass. It is reduced to the element by reacting it with hydrogen, producing germanium suitable for infrared optics and semiconductor production:

: GeO₂ + 2 H₂ → Ge + 2 H₂O

The germanium for steel production and other industrial processes is normally reduced using carbon:{{cite journal |journal=Minerals Engineering |date=2004 |pages=393–402 |doi=10.1016/j.mineng.2003.11.014 |title=Review of germanium processing worldwide |issue=3 |author=Moskalyk, R. R. |volume=17 |bibcode=2004MiEng..17..393M}}

: GeO₂ + C → Ge + CO₂

The major global end uses for germanium were electronics and solar applications, fiber-optic systems, infrared optics, and polymerization catalysts. Other uses included chemotherapy, metallurgy, and phosphors.{{Cite web |last=Mineral |first=Commodity |date=January 4, 2024 |title=Mineral Commodity Summaries 2024 |url=https://pubs.usgs.gov/periodicals/mcs2024/mcs2024-germanium.pdf |access-date=May 14, 2025 |website=Mineral Commodity}}

File:Singlemode fibre structure.svg of the core silica (Item 1). {{olist

|Core 8 µm

|Cladding 125 µm

|Buffer 250 µm

|Jacket 400 µm

}}]]

The notable properties of germania (GeO₂) are its high index of refraction and its low optical dispersion. These make it especially useful for wide-angle camera lenses, microscopy, and the core part of optical fibers.{{cite journal |title=Infrared Detector Arrays for Astronomy |journal=Annual Review of Astronomy and Astrophysics |date=2007 |doi=10.1146/annurev.astro.44.051905.092436 |last=Rieke |first=G. H. |s2cid=26285029 |volume=45 |issue=1 |pages=77–115 |bibcode=2007ARA&A..45...77R}}{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/germanium/220400.pdf |title=Germanium |first=Robert D. Jr. |last=Brown |publisher=U.S. Geological Survey |year=2000 |access-date=2008-09-22 |archive-date=2011-06-08 |archive-url=https://web.archive.org/web/20110608071221/http://minerals.usgs.gov/minerals/pubs/commodity/germanium/220400.pdf |url-status=live}} It has replaced titania as the dopant for silica fiber, eliminating the subsequent heat treatment that made the fibers brittle.{{cite web |url=http://ptgmedia.pearsoncmg.com/images/1587051052/samplechapter/1587051052content.pdf |title=Chapter III: Optical Fiber For Communications |publisher=Stanford Research Institute |access-date=2008-08-22 |archive-date=2014-12-05 |archive-url=https://web.archive.org/web/20141205210827/http://ptgmedia.pearsoncmg.com/images/1587051052/samplechapter/1587051052content.pdf |url-status=live}} At the end of 2002, the fiber optics industry consumed 60% of the annual germanium use in the United States, but this is less than 10% of worldwide consumption. GeSbTe is a phase change material used for its optic properties, such as that used in rewritable DVDs.{{cite web |url=http://www.osta.org/technology/pdf/dvdqa.pdf |archive-url=https://web.archive.org/web/20090419202545/http://www.osta.org/technology/pdf/dvdqa.pdf |archive-date=2009-04-19 |title=Understanding Recordable & Rewritable DVD |edition=First |access-date=2008-09-22 |publisher=Optical Storage Technology Association (OSTA)}}

Because germanium is transparent in the infrared wavelengths, it is an important infrared optical material that can be readily cut and polished into lenses and windows. It is especially used as the front optic in thermal imaging cameras working in the 8 to 14 micron range for passive thermal imaging and for hot-spot detection in military, mobile night vision, and fire fighting applications. It is used in infrared spectroscopes and other optical equipment that require extremely sensitive infrared detectors. It has a very high refractive index (4.0) and must be coated with anti-reflection agents. Particularly, a very hard special antireflection coating of diamond-like carbon (DLC), refractive index 2.0, is a good match and produces a diamond-hard surface that can withstand much environmental abuse.{{cite journal |first=Alan H. |last=Lettington |doi=10.1016/S0008-6223(98)00062-1 |title=Applications of diamond-like carbon thin films |volume=36 |issue=5–6 |date=1998 |pages=555–560 |journal=Carbon |bibcode=1998Carbo..36..555L}}{{cite journal |first=Michael N. |last=Gardos |author2=Bonnie L. Soriano |author3=Steven H. Propst |title=Study on correlating rain erosion resistance with sliding abrasion resistance of DLC on germanium |journal=Proc. SPIE |volume=1325 |page=99 |date=1990 |doi=10.1117/12.22449 |issue=Mechanical Properties |series=SPIE Proceedings |editor1-last=Feldman |editor1-first=Albert |editor2-last=Holly |editor2-first=Sandor |bibcode=1990SPIE.1325...99G |s2cid=137425193}}

Germanium can be alloyed with silicon, and silicon–germanium alloys are rapidly becoming an important semiconductor material for high-speed integrated circuits. Circuits using the properties of Si-SiGe heterojunctions can be much faster than those using silicon alone.{{cite journal |doi=10.1109/TED.2003.810484 |title=SiGe HBT and BiCMOS technologies for optical transmission and wireless communication systems |date=2003 |last=Washio |first=K. |journal=IEEE Transactions on Electron Devices |volume=50 |issue=3 |pages=656–668 |bibcode=2003ITED...50..656W}} The SiGe chips, with high-speed properties, can be made with low-cost, well-established production techniques of the silicon chip industry.

High efficiency solar panels are a major use of germanium. Because germanium and gallium arsenide have nearly identical lattice constant, germanium substrates can be used to make gallium-arsenide solar cells.{{cite journal |doi=10.1002/pip.446 |title=Space and terrestrial photovoltaics: synergy and diversity |date=2002 |last1=Bailey |first1=Sheila G. |journal=Progress in Photovoltaics: Research and Applications |volume=10 |issue=6 |pages=399–406 |last2=Raffaelle |first2=Ryne |last3=Emery |first3=Keith |hdl=2060/20030000611 |bibcode=2002sprt.conf..202B |s2cid=98370426 |hdl-access=free}} Germanium is the substrate of the wafers for high-efficiency multijunction photovoltaic cells for space applications, such as the Mars Exploration Rovers, which use triple-junction gallium arsenide on germanium cells.{{cite journal |doi=10.1016/S0094-5765(02)00287-4 |title=The performance of gallium arsenide/germanium solar cells at the Martian surface |date=January 2004 |first=D. |last=Crisp |author2=Pathare, A. |author3=Ewell, R. C. |journal=Acta Astronautica |volume=54 |issue=2 |pages=83–101 |bibcode=2004AcAau..54...83C}} High-brightness LEDs, used for automobile headlights and to backlight LCD screens, are also an important application.

Germanium-on-insulator (GeOI) substrates are seen as a potential replacement for silicon on miniaturized chips. CMOS circuit based on GeOI substrates has been reported recently.{{cite journal |first1=Heng |last1=Wu |first2=Peide D. |last2=Ye |date=August 2016 |title=Fully Depleted Ge CMOS Devices and Logic Circuits on Si |journal=IEEE Transactions on Electron Devices |volume=63 |issue=8 |pages=3028–3035 |doi=10.1109/TED.2016.2581203 |bibcode=2016ITED...63.3028W |s2cid=3231511 |url=https://engineering.purdue.edu/~yep/Papers/TED_Ge%20Fully%20Depleted%20CMOS_2016.pdf |access-date=2019-03-04 |archive-date=2019-03-06 |archive-url=https://web.archive.org/web/20190306044456/https://engineering.purdue.edu/~yep/Papers/TED_Ge%20Fully%20Depleted%20CMOS_2016.pdf |url-status=live}} Other uses in electronics include phosphors in fluorescent lamps and solid-state light-emitting diodes (LEDs). Germanium transistors are still used in some effects pedals by musicians who wish to reproduce the distinctive tonal character of the "fuzz"-tone from the early rock and roll era, most notably the Dallas Arbiter Fuzz Face.{{cite journal |author=Szweda, Roy |date=2005 |title=Germanium phoenix |journal=III-Vs Review |volume=18 |issue=7 |page=55 |doi=10.1016/S0961-1290(05)71310-7}}

Germanium has been studied as a potential material for implantable bioelectronic sensors that are resorbed in the body without generating harmful hydrogen gas, replacing zinc oxide- and indium gallium zinc oxide-based implementations.{{ cite journal |last1=Zhao |first1=H. |last2=Xue |first2=Z. |last3=Wu |first3=X. |display-authors=2 |date=21 July 2022 |title=Biodegradable germanium electronics for integrated biosensing of physiological signals. |journal=npj Flexible Electronics |volume=6 |at=63 |doi=10.1038/s41528-022-00196-2 |s2cid=250702946 |doi-access=free}}

Germanium was also used to create many of the circuits found in some of the very first pieces of electronic musical gear, initially 1950s, primarily in early transistor-based circuits. The first guitar effects pedals in the 1960s – Fuzz pedals like the Maestro FZ-1 (1962), Dallas-Arbiter Fuzz Face (1966), and Tone Bender (1965) - used germanium transistors.{{Cite web |last=joe |date=2012-01-03 |title=The Germanium Mystique |url=https://tonefiend.com/diy/the-germanium-mystique/ |access-date=2025-02-21 |website=tonefiend.com |language=en-US}} Silicon diodes are more frequently used in more modern equipment, but germanium diodes are still used in some applications as they have lower barrier potential and smoother transconductance curves, leading to less harsh clipping.{{Citation |last=Dailey |first=Denton J. |title=Guitar Effects Circuits |date=2013 |work=Electronics for Guitarists |pages=199–200 |url=https://link.springer.com/chapter/10.1007/978-1-4614-4087-1_5 |access-date=2025-02-21 |place=New York, NY |publisher=Springer New York |language=en |doi=10.1007/978-1-4614-4087-1_5 |isbn=978-1-4614-4086-4|url-access=subscription }}

File:Pet Flasche.JPG bottle|alt=Photo of a standard transparent plastic bottle.]]

Germanium dioxide is also used in catalysts for polymerization in the production of polyethylene terephthalate (PET).{{cite journal |last=Thiele |first=Ulrich K. |date=2001 |title=The Current Status of Catalysis and Catalyst Development for the Industrial Process of Poly(ethylene terephthalate) Polycondensation |journal=International Journal of Polymeric Materials |volume=50 |issue=3 |pages=387–394 |doi=10.1080/00914030108035115 |s2cid=98758568}} The high brilliance of this polyester is especially favored for PET bottles marketed in Japan. In the United States, germanium is not used for polymerization catalysts.

Due to the similarity between silica (SiO₂) and germanium dioxide (GeO₂), the silica stationary phase in some gas chromatography columns can be replaced by GeO₂.{{cite journal |title=Germania-Based, Sol-Gel Hybrid Organic-Inorganic Coatings for Capillary Microextraction and Gas Chromatography |last1=Fang |first1=Li |last2=Kulkarni |first2=Sameer |last3=Alhooshani |first3=Khalid |last4=Malik |first4=Abdul |journal=Anal. Chem. |volume=79 |issue=24 |pages=9441–9451 |date=2007 |doi=10.1021/ac071056f |pmid=17994707}}

In recent years germanium has seen increasing use in precious metal alloys. In sterling silver alloys, for instance, it reduces firescale, increases tarnish resistance, and improves precipitation hardening. A tarnish-proof silver alloy trademarked Argentium contains 1.2% germanium.

Semiconductor detectors made of single crystal high-purity germanium can precisely identify radiation sources—for example in airport security.{{cite web |title=Performance of Light-Weight, Battery-Operated, High Purity Germanium Detectors for Field Use |first1=Ronald |last1=Keyser |last2=Twomey |first2=Timothy |last3=Upp |first3=Daniel |url=http://www.ortec-online.com/papers/inmm_2003_keyser.pdf |access-date=2008-09-06 |publisher=Oak Ridge Technical Enterprise Corporation (ORTEC) |archive-url=https://web.archive.org/web/20071026162911/http://www.ortec-online.com/papers/inmm_2003_keyser.pdf |archive-date=October 26, 2007 |url-status=dead}} Germanium is useful for monochromators for beamlines used in single crystal neutron scattering and synchrotron X-ray diffraction. The reflectivity has advantages over silicon in neutron and high energy X-ray applications.{{cite journal |doi=10.1142/S0218301396000062 |date=1996 |journal=International Journal of Modern Physics E |volume=5 |issue=1 |pages=131–151 |title=Optimization of Germanium for Neutron Diffractometers |bibcode=1996IJMPE...5..131A |last1=Ahmed |first1=F. U. |last2=Yunus |first2=S. M. |last3=Kamal |first3=I. |last4=Begum |first4=S. |last5=Khan |first5=Aysha A. |last6=Ahsan |first6=M. H. |last7=Ahmad |first7=A. A. Z.}} Crystals of high purity germanium are used in detectors for gamma spectroscopy and the search for dark matter.{{cite journal |doi=10.1016/j.nuclphysa.2005.02.155 |title=Astrophysical constraints from gamma-ray spectroscopy |date=2006 |last1=Diehl |first1=R. |journal=Nuclear Physics A |volume=777 |issue=2006 |pages=70–97 |last2=Prantzos |first2=N. |last3=Vonballmoos |first3=P. |arxiv=astro-ph/0502324 |bibcode=2006NuPhA.777...70D |citeseerx=10.1.1.256.9318 |s2cid=2360391}} Germanium crystals are also used in X-ray spectrometers for the determination of phosphorus, chlorine and sulfur.Eugene P. Bertin (1970). Principles and practice of X-ray spectrometric analysis, Chapter 5.4 – Analyzer crystals, Table 5.1, p. 123; Plenum Press

Germanium is emerging as an important material for spintronics and spin-based quantum computing applications. In 2010, researchers demonstrated room temperature spin transport{{Cite journal |last1=Shen |first1=C. |last2=Trypiniotis |first2=T. |last3=Lee |first3=K. Y. |last4=Holmes |first4=S. N. |last5=Mansell |first5=R. |last6=Husain |first6=M. |last7=Shah |first7=V. |last8=Li |first8=X. V. |last9=Kurebayashi |first9=H. |date=2010-10-18 |title=Spin transport in germanium at room temperature |journal=Applied Physics Letters |volume=97 |issue=16 |page=162104 |doi=10.1063/1.3505337 |issn=0003-6951 |bibcode=2010ApPhL..97p2104S |url=https://eprints.soton.ac.uk/271616/1/Gespin.pdf |access-date=2018-11-16 |archive-date=2017-09-22 |archive-url=https://web.archive.org/web/20170922180043/https://eprints.soton.ac.uk/271616/1/Gespin.pdf |url-status=live}} and more recently donor electron spins in germanium has been shown to have very long coherence times.{{Cite journal |last1=Sigillito |first1=A. J. |last2=Jock |first2=R. M. |last3=Tyryshkin |first3=A. M. |last4=Beeman |first4=J. W. |last5=Haller |first5=E. E. |last6=Itoh |first6=K. M. |last7=Lyon |first7=S. A. |date=2015-12-07 |title=Electron Spin Coherence of Shallow Donors in Natural and Isotopically Enriched Germanium |journal=Physical Review Letters |volume=115 |issue=24 |pages=247601 |doi=10.1103/PhysRevLett.115.247601 |pmid=26705654 |arxiv=1506.05767 |bibcode=2015PhRvL.115x7601S |s2cid=13299377}}

Germanium is not considered essential to the health of plants or animals. Germanium in the environment has little or no health impact. This is primarily because it usually occurs only as a trace element in ores and carbonaceous materials, and the various industrial and electronic applications involve very small quantities that are not likely to be ingested. For similar reasons, end-use germanium has little impact on the environment as a biohazard. Some reactive intermediate compounds of germanium are poisonous (see precautions, below).{{cite report |url=http://minerals.usgs.gov/minerals/pubs/commodity/germanium/220798.pdf |publisher=US Geological Surveys |access-date=2008-09-09 |title=Commodity Survey:Germanium |first=Robert D. Jr. |last=Brown |date= |archive-date=2018-03-04 |archive-url=https://web.archive.org/web/20180304113236/https://minerals.usgs.gov/minerals/pubs/commodity/germanium/220798.pdf |url-status=live}}

Germanium supplements, made from both organic and inorganic germanium, have been marketed as an alternative medicine capable of treating leukemia and lung cancer. There is, however, no medical evidence of benefit; some evidence suggests that such supplements are actively harmful.{{cite book |publisher=American Cancer Society |title=American Cancer Society Complete Guide to Complementary and Alternative Cancer Therapies |edition=2nd |year=2009 |isbn=978-0944235713 |editor=Ades TB |pages=[https://archive.org/details/americancancerso0000unse/page/360 360–363] |chapter=Germanium |chapter-url=https://archive.org/details/americancancerso0000unse/page/360}} U.S. Food and Drug Administration (FDA) research has concluded that inorganic germanium, when used as a nutritional supplement, "presents potential human health hazard".{{cite journal |last=Tao |first=S. H. |author2=Bolger, P. M. |date=June 1997 |title=Hazard Assessment of Germanium Supplements |journal=Regulatory Toxicology and Pharmacology |volume=25 |issue=3 |pages=211–219 |doi=10.1006/rtph.1997.1098 |pmid=9237323 |url=https://zenodo.org/record/1229957 |access-date=2019-06-30 |archive-date=2020-03-10 |archive-url=https://web.archive.org/web/20200310041729/https://zenodo.org/record/1229957 |url-status=live}}

Some germanium compounds have been administered by alternative medical practitioners as non-FDA-allowed injectable solutions. Soluble inorganic forms of germanium used at first, notably the citrate-lactate salt, resulted in some cases of renal dysfunction, hepatic steatosis, and peripheral neuropathy in individuals using them over a long term. Plasma and urine germanium concentrations in these individuals, several of whom died, were several orders of magnitude greater than endogenous levels. A more recent organic form, beta-carboxyethylgermanium sesquioxide (propagermanium), has not exhibited the same spectrum of toxic effects.{{cite book |author=Baselt, R. |title=Disposition of Toxic Drugs and Chemicals in Man |edition=8th |publisher=Biomedical Publications |place=Foster City, CA |date=2008 |pages=693–694}}

Certain compounds of germanium have low toxicity to mammals, but have toxic effects against certain bacteria.{{cite book |last=Emsley |first=John |title=Nature's Building Blocks |publisher=Oxford University Press |date=2001 |location=Oxford |pages=506–510 |isbn=978-0-19-850341-5}}

While use of germanium itself does not require precautions, some of germanium's artificially produced compounds are quite reactive and present an immediate hazard to human health on exposure. For example, Germanium tetrachloride and germane (GeH₄) are a liquid and gas, respectively, that can be very irritating to the eyes, skin, lungs, and throat.{{cite journal |first=G. B. |last=Gerber |author2=Léonard, A. |date=1997 |title=Mutagenicity, carcinogenicity and teratogenicity of germanium compounds |journal=Regulatory Toxicology and Pharmacology |volume=387 |issue=3 |pages=141–146 |doi=10.1016/S1383-5742(97)00034-3 |pmid=9439710 |bibcode=1997MRRMR.387..141G}}

• Germanene
• Vitrain
• History of the transistor

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{{EB1911 poster|Germanium}}

• [http://www.periodicvideos.com/videos/032.htm Germanium] at The Periodic Table of Videos (University of Nottingham)

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