Germanium

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Not to be confused with geranium.
Germanium, 32Ge
Grayish lustrous block with uneven cleaved surface
Germanium
Pronunciation/dʒɜːrˈmeɪniəm/ ​(jur-MAY-nee-əm)
Appearancegrayish-white
Standard atomic weight Ar°(Ge)
Germanium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Si
↑
Ge
↓
Sn
gallium ← germanium → arsenic
kJ/mol
Heat of vaporization334 kJ/mol
Molar heat capacity23.222 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1644 1814 2023 2287 2633 3104
Atomic properties
Discovery
Clemens Winkler (1886)
Isotopes of germanium
Main isotopes[8] Decay
abun­dance half-life (t1/2) mode pro­duct
68Ge synth 270.8 d ε
68Ga
70Ge 20.5%
stable
71Ge synth 11.3 d ε
71Ga
72Ge 27.4% stable
73Ge 7.76% stable
74Ge 36.5% stable
76Ge 7.75% 1.78×1021 y
β−β−
76Se
 Category: Germanium
| references

Germanium is a

symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors silicon and tin. Like silicon, germanium naturally reacts and forms complexes with oxygen
in nature.

Because it seldom appears in high concentration, germanium was found comparatively late in the

discovery of the elements. Germanium ranks 52nd in abundance of the elements in the Earth's crust. In 1869, Dmitri Mendeleev predicted its existence and some of its properties from its position on his periodic table, and called the element ekasilicon. On February 6, 1886, Clemens Winkler at Freiberg University found the new element, along with silver and sulfur, in the mineral argyrodite. Winkler named the element after his country of birth, Germany. Germanium is mined primarily from sphalerite (the primary ore of zinc), though germanium is also recovered commercially from silver, lead, and copper ores
.

Elemental germanium is used as a semiconductor in

organogermanium compounds, such as tetraethylgermanium, useful in organometallic chemistry. Germanium is considered a technology-critical element.[9]

Germanium is not thought to be an essential element for any

nephrotoxic, and synthetic chemically reactive germanium compounds with halogens and hydrogen
are irritants and toxins.

History

Prediction of germanium, "?=70" (periodic table 1869)

In his report on The Periodic Law of the Chemical Elements in 1869, the Russian chemist

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.[note 1] 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.[12][13] 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.[note 2] 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).[note 3] So instead, Winkler named the new element germanium (from the Latin word, Germania, for Germany) in honor of his homeland.[13]
Argyrodite proved empirically to be Ag8GeS6. Because this new element showed some similarities with the elements
Lecoq de Boisbaudran deduced 72.3 by a comparison of the lines in the spark spectrum of the element.[22]

Winkler was able to prepare several new compounds of germanium, including

tetraethylgermane (Ge(C2H5)4), the first organogermane.[12] 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:[12]

Property Ekasilicon
Mendeleev
prediction (1871)		 Germanium
Winkler
discovery (1887)
atomic mass 72.64 72.63
density (g/cm3) 5.5 5.35
melting point (°C) high 947
color gray gray
oxide type refractory dioxide refractory dioxide
oxide density (g/cm3) 4.7 4.7
oxide activity feebly basic feebly basic
chloride boiling point (°C) under 100 86 (GeCl4)
chloride density (g/cm3) 1.9 1.9

Until the late 1930s, germanium was thought to be a poorly conducting metal.[23] 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.[24][25] The first major use was the point-contact Schottky diodes for radar pulse detection during the War.[23] The first silicon–germanium alloys were obtained in 1955.[26] 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 40 metric tons (44 short tons).[27]

The development of the germanium

solid state electronics.[29] 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.[30] 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.[31]

Meanwhile, the demand for germanium for

catalysts increased dramatically.[27] These end uses represented 85% of worldwide germanium consumption in 2000.[30] 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.[27]

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,[27] the price of germanium was almost $800 per kg.[27]

Characteristics

Under

allotrope known as α-germanium, which has a metallic luster and a diamond cubic crystal structure, the same as diamond.[30]
While in crystal form, germanium has a displacement threshold energy of .[33] At pressures above 120 kbar, germanium becomes the allotrope β-germanium with the same structure as β-tin.[34] 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.[34]

Germanium is a

Zone refining techniques have led to the production of crystalline germanium for semiconductors that has an impurity of only one part in 1010,[35]
making it one of the purest materials ever obtained.[36] 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.[37]

Pure germanium is known to spontaneously extrude very long

electrical short.[38]

Chemistry

Main article: Germanium compounds

Elemental germanium starts to oxidize slowly in air at around 250 °C, forming

alkalis but dissolves slowly in hot concentrated sulfuric and nitric acids and reacts violently with molten alkalis to produce germanates ([GeO
3]2−
). Germanium occurs mostly in the oxidation state +4 although many +2 compounds are known.[40] Other oxidation states are rare: +3 is found in compounds such as Ge2Cl6, and +3 and +1 are found on the surface of oxides,[41] or negative oxidation states in germanides, such as −4 in Mg
2Ge. 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.[40][42] 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 (GeO
2, germania) and germanium monoxide, (GeO).[34] The dioxide, GeO2, can be obtained by roasting germanium disulfide (GeS
2), and is a white powder that is only slightly soluble in water but reacts with alkalis to form germanates.[34] The monoxide, germanous oxide, can be obtained by the high temperature reaction of GeO2 with elemental Ge.[34] 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.[43][44] Bismuth germanate, Bi4Ge3O12 (BGO), is used as a scintillator.[45]

alkaline carbonates and sulfur, germanium compounds form salts known as thiogermanates.[47]

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.
Germane is similar to methane.

Four tetra

halides are known. Under normal conditions GeI4 is a solid, 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.[34] All the tetrahalides are readily hydrolyzed to hydrated germanium dioxide.[34] GeCl4 is used in the production of organogermanium compounds.[40] All four dihalides are known and in contrast to the tetrahalides are polymeric solids.[40] Additionally Ge2Cl6 and some higher compounds of formula GenCl2n+2 are known.[34] The unusual compound Ge6Cl16 has been prepared that contains the Ge5Cl12 unit with a neopentane structure.[48]

anion.[40] The germanium hydrohalides with one, two and three halogen atoms are colorless reactive liquids.[40]

Skeletal chemical structures outlining an additive chemical reaction including an organogermanium compound.
Nucleophilic addition with an organogermanium compound

The first

free radicals, germylenes (similar to carbenes), and germynes (similar to carbynes).[49][50] 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.[51]

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.[52]

Isotopes

Main article: Isotopes of germanium

Germanium occurs in five natural

77
Se
, releasing high energy electrons in the process.[54] Because of this, it is used in combination with radon for nuclear batteries.[54]

At least 27

radioisotopes have also been synthesized, ranging in atomic mass from 58 to 89. The most stable of these is 68
Ge
, decaying by electron capture with a half-life of 270.95 days. The least stable is 60
Ge
, with a half-life of 30 ms. While most of germanium's radioisotopes decay by beta decay, 61
Ge
 and 64
Ge
 decay by
β+
 delayed proton emission.[53] 84
Ge
 through 87
Ge
 isotopes also exhibit minor
β−
 delayed neutron emission decay paths.[53]

Occurrence

See also: Category:Germanium minerals
A brown block of irregular shape and surface, about 6 cm in size.
Renierite

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.[55] Germanium has been detected in some of the most distant stars[56] and in the atmosphere of Jupiter.[57]

Germanium's abundance

Xilinhaote, Inner Mongolia, contain an estimated 1600 tonnes of germanium.[58]

Production

About 118 tonnes of germanium were produced in 2011 worldwide, mostly in China (80 t), Russia (5 t) and United States (3 t).[30] Germanium is recovered as a by-product from sphalerite zinc ores where it is concentrated in amounts as great as 0.3%,[65] especially from low-temperature sediment-hosted, massive Zn–Pb–Cu(–Ba) deposits and carbonate-hosted Zn–Pb deposits.[66] 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.[67] In 2007 35% of the demand was met by recycled germanium.[58]

Year Cost
($/kg)[68]
1999 1,400
2000 1,250
2001 890
2002 620
2003 380
2004 600
2005 660
2006 880
2007 1,240
2008 1,490
2009 950
2010 940
2011 1,625
2012 1,680
2013 1,875
2014 1,900
2015 1,760
2016 950
2017 1,358
2018 1,300
2019 1,240
2020 1,000

While it is produced mainly from

Xilinhaote, Inner Mongolia.[58]

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:[69]

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.[69] 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:[70]

GeO2 + C → Ge + CO2

Applications

The major end uses for germanium in 2007, worldwide, were estimated to be: 35% for

fiber-optics, 30% infrared optics, 15% polymerization catalysts, and 15% electronics and solar electric applications.[30] The remaining 5% went into such uses as phosphors, metallurgy, and chemotherapy.[30]

Optics

A drawing of four concentric cylinders.
A typical single-mode optical fiber. Germanium oxide is a dopant of the core silica (Item 1).
  1. Core 8 µm
  2. Cladding 125 µm
  3. Buffer 250 µm
  4. Jacket 400 µm

The notable properties of

rewritable DVDs.[74]

Because germanium is transparent in the infrared wavelengths, it is an important

spectroscopes and other optical equipment that require extremely sensitive infrared detectors.[72] 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.[75][76]

Electronics

Germanium can be alloyed with

silicon chip industry.[30]

High efficiency

multijunction photovoltaic cells for space applications, such as the Mars Exploration Rovers, which use triple-junction gallium arsenide on germanium cells.[79] High-brightness LEDs, used for automobile headlights and to backlight LCD screens, are also an important application.[30]

Germanium-on-insulator (GeOI) substrates are seen as a potential replacement for silicon on miniaturized chips.

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.[81]

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.[82]

Other uses

Photo of a standard transparent plastic bottle.
A PET bottle

Germanium dioxide is also used in

catalysts for polymerization in the production of polyethylene terephthalate (PET).[83] The high brilliance of this polyester is especially favored for PET bottles marketed in Japan.[83] In the United States, germanium is not used for polymerization catalysts.[30]

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.[84]

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.[30]

high energy X-ray applications.[86] Crystals of high purity germanium are used in detectors for gamma spectroscopy and the search for dark matter.[87] Germanium crystals are also used in X-ray spectrometers for the determination of phosphorus, chlorine and sulfur.[88]

Germanium is emerging as an important material for spintronics and spin-based quantum computing applications. In 2010, researchers demonstrated room temperature spin transport[89] and more recently donor electron spins in germanium has been shown to have very long coherence times.[90]

Strategic importance

Due to its use in advanced electronics and optics, Germanium is considered a technology-critical element (by e.g. the European Union), essential to fulfill the green and digital transition. As China controls 60% of global Germanium production it holds a dominant position over the world's supply chains.

On 3 July 2023 China suddenly imposed restrictions on the exports of germanium (and gallium), ratcheting up trade tensions with Western allies. Invoking "national security interests," the Chinese Ministry of Commerce informed that companies that intend to sell products containing germanium would need an export licence. The products/compounds targeted are: germanium dioxide, germanium epitaxial growth substrate, germanium ingot, germanium metal, germanium tetrachloride and zinc germanium phosphide. It sees such products as "dual-use" items that may have military purposes and therefore warrant an extra layer of oversight.[citation needed]

The new dispute opened a new chapter in the increasingly fierce technology race that has pitted the United States, and to a lesser extent Europe, against China. The US wants its allies to heavily curb, or downright prohibit, advanced electronic components bound to the Chinese market in order to prevent Beijing from securing global technology supremacy. China denied any tit-for-tat intention behind the Germanium export restrictions.[91][92][93]

Following China's export restrictions, Russian state-owned company Rostec announced an increase in germanium production to meet domestic demand.[94]

Germanium and health

Germanium is not considered essential to the health of plants or animals.[95] 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.[30] 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).[96]

Germanium supplements, made from both organic and inorganic germanium, have been marketed as an

health hazard".[51]

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

endogenous levels. A more recent organic form, beta-carboxyethylgermanium sesquioxide (propagermanium), has not exhibited the same spectrum of toxic effects.[97]

Certain compounds of germanium have low toxicity to

bacteria.[32]

Precautions for chemically reactive germanium compounds

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.[98]

See also

Notes

  1. ^ From Greek, argyrodite means silver-containing.[11]
  2. ^ 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.[14] James Challis started searching for it in July 1846, and he sighted this planet on September 23, 1846.[15]
  3. ^ 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.[16][17] However this metal was later recognized to be an alloy of the elements niobium and tantalum.[18] 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.[19]

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    • External links

    Wikisource has the text of the 1911 Encyclopædia Britannica article "Germanium".
    • Germanium at
      The Periodic Table of Videos
       (University of Nottingham)

    Retrieved from "https://en.wikipedia.org/w/index.php?title=Germanium&oldid=1220211479"