Germanium

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Germanium, 32Ge
Polycrystalline-germanium.jpg
Germanium
Pronunciation /ɜːrˈmniəm/ (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
galliumgermaniumarsenic
Atomic number (Z)32
Group group 14 (carbon group)
Period period 4
Block   p-block
Electron configuration [ Ar ] 3d10 4s2 4p2
Electrons per shell2, 8, 18, 4
Physical properties
Phase at  STP solid
Melting point 1211.40  K (938.25 °C,1720.85 °F)
Boiling point 3106 K(2833 °C,5131 °F)
Density (at 20° C)5.327 g/cm3 [3]
when liquid (at  m.p.)5.60 g/cm3
Heat of fusion 36.94  kJ/mol
Heat of vaporization 334 kJ/mol
Molar heat capacity 23.222 J/(mol·K)
Vapor pressure
P (Pa)1101001 k10 k100 k
at T (K)164418142023228726333104
Atomic properties
Oxidation states −4, −3, −2, −1, 0, [4] +1, +2, +3, +4 (an  amphoteric oxide)
Electronegativity Pauling scale: 2.01
Ionization energies
  • 1st: 762 kJ/mol
  • 2nd: 1537.5 kJ/mol
  • 3rd: 3302.1 kJ/mol
Atomic radius empirical:122  pm
Covalent radius 122 pm
Van der Waals radius 211 pm
Germanium spectrum visible.png
Spectral lines of germanium
Other properties
Natural occurrence primordial
Crystal structure face-centered diamond-cubic (cF8)
Lattice constant
Diamond cubic crystal structure.svg
a = 565.774 pm (at 20 °C) [3]
Thermal expansion 5.79×10−6/K (at 20 °C) [3]
Thermal conductivity 60.2 W/(m⋅K)
Electrical resistivity 1 Ω⋅m(at 20 °C)
Band gap 0.67  eV (at 300 K)
Magnetic ordering diamagnetic [5]
Molar magnetic susceptibility −76.84×10−6 cm3/mol [6]
Young's modulus 103 GPa [7]
Shear modulus 41 GPa [7]
Bulk modulus 75 GPa [7]
Speed of sound thin rod5400 m/s(at 20 °C)
Poisson ratio 0.26 [7]
Mohs hardness 6.0
CAS Number 7440-56-4
History
Namingafter Germany, homeland of the discoverer
Prediction Dmitri Mendeleev (1869)
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
70Ge20.5% stable
71Gesynth11.3 dε 71Ga
72Ge27.4%stable
73Ge7.76%stable
74Ge36.5%stable
76Ge7.75%1.78×1021 y ββ 76Se
Symbol category class.svg  Category: Germanium
| references

Germanium is a chemical element; it has 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.

Contents

Because it seldom appears in high concentration, germanium was found comparatively late in the discovery of the elements. Germanium ranks 55th in relative 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 transistors and various other electronic devices. Historically, the first decade of semiconductor electronics was based entirely on germanium. Presently, the major end uses are fibre-optic systems, infrared optics, solar cell applications, and light-emitting diodes (LEDs). Germanium compounds are also used for polymerization catalysts and have most recently found use in the production of nanowires. This element forms a large number of 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 living organism. Similar to silicon and aluminium, naturally-occurring germanium compounds tend to be insoluble in water and thus have little oral toxicity. However, synthetic soluble germanium salts are nephrotoxic, and synthetic chemically reactive germanium compounds with halogens and hydrogen are irritants and toxins.

History

Prediction of germanium, "?=70" (periodic table 1869) Mendeleev 1869 prediction of germanium (detail).svg
Prediction of germanium, "?=70" (periodic table 1869)

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. [10] 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. [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 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. [13] [20] With further material from 500 kg of ore from the mines in Saxony, Winkler confirmed the chemical properties of the new element in 1887. [12] [13] [21] He also determined an atomic weight of 72.32 by analyzing pure germanium tetrachloride (GeCl
4
), while 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 fluorides, chlorides, sulfides, dioxide, and 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]

PropertyEkasilicon
Mendeleev
prediction (1871)
Germanium
Winkler
discovery (1887)
atomic mass72.6472.63
density (g/cm3)5.55.35
melting point (°C)high947
colorgraygray
oxide type refractory dioxiderefractory dioxide
oxide density (g/cm3)4.74.7
oxide activityfeebly basicfeebly basic
chloride boiling point (°C)under 10086 (GeCl4)
chloride density (g/cm3)1.91.9

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 transistor in 1948 [28] opened the door to countless applications of 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 fiber optic communication networks, infrared night vision systems, and polymerization 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 standard conditions, germanium is a brittle, silvery-white, semi-metallic element. [32] This form constitutes an 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 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, [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 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. [38]

Chemistry

Elemental germanium starts to oxidize slowly in air at around 250 °C, forming GeO2 . [39] 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 ([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
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. [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]

Binary compounds with other chalcogens are also known, such as the disulfide (GeS
2
) and diselenide (GeSe
2
), and the monosulfide (GeS), monoselenide (GeSe), and monotelluride (GeTe). [40] GeS2 forms as a white precipitate when hydrogen sulfide is passed through strongly acid solutions containing Ge(IV). [40] 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. [46] 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. [34] Upon melting with alkaline carbonates and sulfur, germanium compounds form salts known as thiogermanates. [47]

Germane is similar to methane. Germane-2D-dimensions.png
Germane is similar to methane.

Four tetrahalides 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]

Germane (GeH4) is a compound similar in structure to methane. Polygermanes—compounds that are similar to alkanes—with formula GenH2n+2 containing up to five germanium atoms are known. [40] The germanes are less volatile and less reactive than their corresponding silicon analogues. [40] GeH4 reacts with alkali metals in liquid ammonia to form white crystalline MGeH3 which contain the GeH3 anion. [40] The germanium hydrohalides with one, two and three halogen atoms are colorless reactive liquids. [40]

Nucleophilic addition with an organogermanium compound NucleophilicAdditionWithOrganogermanium.png
Nucleophilic addition with an organogermanium compound

The first organogermanium compound was synthesized by Winkler in 1887; the reaction of germanium tetrachloride with diethylzinc yielded tetraethylgermane (Ge(C
2
H
5
)
4
). [12] Organogermanes of the type R4Ge (where R is an alkyl) such as tetramethylgermane (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 ((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). [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

Germanium occurs in five natural isotopes: 70
Ge
, 72
Ge
, 73
Ge
, 74
Ge
, and 76
Ge
. Of these, 76
Ge
is very slightly radioactive, decaying by double beta decay with a half-life of 1.78×1021 years. 74
Ge
is the most common isotope, having a natural abundance of approximately 36%. 76
Ge
is the least common with a natural abundance of approximately 7%. [53] When bombarded with alpha particles, the isotope 72
Ge
will generate stable 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

Renierite Renierit.JPG
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 in the Earth's crust is approximately 1.6  ppm. [58] Only a few minerals like argyrodite, briartite, germanite, renierite and sphalerite contain appreciable amounts of germanium. [30] [59] Only few of them (especially germanite) are, very rarely, found in mineable amounts. [60] [61] [62] Some zinc–copper–lead ore bodies contain enough germanium to justify extraction from the final ore concentrate. [58] 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. [63] [64] The highest concentration ever found was in Hartley coal ash with as much as 1.6% germanium. [63] [64] The coal deposits near 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 ZnPbCu(–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]

YearCost
($/kg) [68]
19991,400
20001,250
2001890
2002620
2003380
2004600
2005660
2006880
20071,240
20081,490
2009950
2010940
20111,625
20121,680
20131,875
20141,900
20151,760
2016950
20171,358
20181,300
20191,240
20201,000

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. [69] 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. [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 typical single-mode optical fiber. Germanium oxide is a dopant of the core silica (Item 1).
Core 8 um
Cladding 125 um
Buffer 250 um
Jacket 400 um Singlemode fibre structure.svg
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 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. [71] [72] It has replaced titania as the dopant for silica fiber, eliminating the subsequent heat treatment that made the fibers brittle. [73] 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. [72] GeSbTe is a phase change material used for its optic properties, such as that used in rewritable DVDs. [74]

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. [70] It is used in infrared 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, and silicon–germanium alloys are rapidly becoming an important semiconductor material for high-speed integrated circuits. Circuits utilizing the properties of Si-SiGe heterojunctions can be much faster than those using silicon alone. [77] The SiGe chips, with high-speed properties, can be made with low-cost, well-established production techniques of the silicon chip industry. [30]

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. [78] 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. [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. [30] CMOS circuit based on GeOI substrates has been reported recently. [80] Other uses in electronics include phosphors in fluorescent lamps [35] and solid-state light-emitting diodes (LEDs). [30] 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. [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

A PET bottle Pet Flasche.JPG
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]

Semiconductor detectors made of single crystal high-purity germanium can precisely identify radiation sources—for example in airport security. [85] 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. [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 alternative medicine capable of treating leukemia and lung cancer. [27] There is, however, no medical evidence of benefit; some evidence suggests that such supplements are actively harmful. [95] U.S. Food and Drug Administration (FDA) research has concluded that inorganic germanium, when used as a nutritional supplement, "presents potential human 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 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. [97]

Certain compounds of germanium have low toxicity to mammals, but have toxic effects against certain 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]

Related Research Articles

<span class="mw-page-title-main">Gallium</span> Chemical element, symbol Ga and atomic number 31

Gallium is a chemical element; it has symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, gallium is in group 13 of the periodic table and is similar to the other metals of the group.

<span class="mw-page-title-main">Silicon</span> Chemical element, symbol Si and atomic number 14

Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic table: carbon is above it; and germanium, tin, lead, and flerovium are below it. It is relatively unreactive. Silicon (Si) element is a significant element that is essential for several physiological and metabolic processes in plants. Si is widely regarded as the predominant semiconductor material due to its versatile applications in various electrical devices such as transistors, solar cells, integrated circuits, and others. These may be due to its significant band gap, expansive optical transmission range, extensive absorption spectrum, surface roughening, and effective anti-reflection coating.

A semiconductor is a material that has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity generally falls as its temperature rises; metals behave in the opposite way. In many cases their conducting properties may be altered in useful ways by introducing impurities ("doping") into the crystal structure. When two differently doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers, which include electrons, ions, and electron holes, at these junctions is the basis of diodes, transistors, and most modern electronics. Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table. After silicon, gallium arsenide is the second-most common semiconductor and is used in laser diodes, solar cells, microwave-frequency integrated circuits, and others. Silicon is a critical element for fabricating most electronic circuits.

<span class="mw-page-title-main">Transistor</span> Solid-state electrically operated switch also used as an amplifier

A transistor is a semiconductor device used to amplify or switch electrical signals and power. It is one of the basic building blocks of modern electronics. It is composed of semiconductor material, usually with at least three terminals for connection to an electronic circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Some transistors are packaged individually, but many more in miniature form are found embedded in integrated circuits. Because transistors are the key active components in practically all modern electronics, many people consider them one of the 20th century's greatest inventions.

<span class="mw-page-title-main">Gallium arsenide</span> Chemical compound

Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a zinc blende crystal structure.

SiGe, or silicon–germanium, is an alloy with any molar ratio of silicon and germanium, i.e. with a molecular formula of the form Si1−xGex. It is commonly used as a semiconductor material in integrated circuits (ICs) for heterojunction bipolar transistors or as a strain-inducing layer for CMOS transistors. IBM introduced the technology into mainstream manufacturing in 1989. This relatively new technology offers opportunities in mixed-signal circuit and analog circuit IC design and manufacture. SiGe is also used as a thermoelectric material for high-temperature applications (>700 K).

<span class="mw-page-title-main">Doping (semiconductor)</span> Intentional introduction of impurities into an intrinsic semiconductor

In semiconductor production, doping is the intentional introduction of impurities into an intrinsic (undoped) semiconductor for the purpose of modulating its electrical, optical and structural properties. The doped material is referred to as an extrinsic semiconductor.

The heterojunction bipolar transistor (HBT) is a type of bipolar junction transistor (BJT) which uses differing semiconductor materials for the emitter and base regions, creating a heterojunction. The HBT improves on the BJT in that it can handle signals of very high frequencies, up to several hundred GHz. It is commonly used in modern ultrafast circuits, mostly radio frequency (RF) systems, and in applications requiring a high power efficiency, such as RF power amplifiers in cellular phones. The idea of employing a heterojunction is as old as the conventional BJT, dating back to a patent from 1951. Detailed theory of heterojunction bipolar transistor was developed by Herbert Kroemer in 1957.

<span class="mw-page-title-main">Germanium tetrachloride</span> Chemical compound

Germanium tetrachloride is a colourless, fuming liquid with a peculiar, acidic odour. It is used as an intermediate in the production of purified germanium metal. In recent years, GeCl4 usage has increased substantially due to its use as a reagent for fiber optic production.

<span class="mw-page-title-main">Hafnium(IV) oxide</span> Chemical compound

Hafnium(IV) oxide is the inorganic compound with the formula HfO
2
. Also known as hafnium dioxide or hafnia, this colourless solid is one of the most common and stable compounds of hafnium. It is an electrical insulator with a band gap of 5.3~5.7 eV. Hafnium dioxide is an intermediate in some processes that give hafnium metal.

<span class="mw-page-title-main">Indium(III) oxide</span> Chemical compound

Indium(III) oxide (In2O3) is a chemical compound, an amphoteric oxide of indium.

Germanium dioxide, also called germanium(IV) oxide, germania, and salt of germanium, is an inorganic compound with the chemical formula GeO2. It is the main commercial source of germanium. It also forms as a passivation layer on pure germanium in contact with atmospheric oxygen.

Organogermanium chemistry is the science of chemical species containing one or more C–Ge bonds. Germanium shares group 14 in the periodic table with carbon, silicon, tin and lead. Historically, organogermanes are considered as nucleophiles and the reactivity of them is between that of organosilicon and organotin compounds. Some organogermanes have enhanced reactivity compared with their organosilicon and organoboron analogues in some cross-coupling reactions.

<span class="mw-page-title-main">Germanium disulfide</span> Chemical compound

Germanium disulfide or Germanium(IV) sulfide is the inorganic compound with the formula GeS2. It is a white high-melting crystalline solid. The compound is a 3-dimensional polymer, in contrast to silicon disulfide, which is a one-dimensional polymer. The Ge-S distance is 2.19 Å.

<span class="mw-page-title-main">Germanate</span> Chemical compound

In chemistry, germanate is a compound containing an oxyanion of germanium. In the naming of inorganic compounds it is a suffix that indicates a polyatomic anion with a central germanium atom, for example potassium hexafluorogermanate, K2GeF6.

<span class="mw-page-title-main">Digermane</span> Chemical compound

Digermane is an inorganic compound with the chemical formula Ge2H6. One of the few hydrides of germanium, it is a colourless liquid. Its molecular geometry is similar to ethane.

<span class="mw-page-title-main">Sodium germanate</span> Chemical compound

Sodium germanate is an inorganic compound with the chemical formula Na2GeO3. It exists as a colorless solid. Sodium germanate is primarily used for the synthesis of other germanium compounds.

Germanium compounds are chemical compounds formed by the element germanium (Ge). 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 ([GeO
3
]2−
). Germanium occurs mostly in the oxidation state +4 although many +2 compounds are known. Other oxidation states are rare: +3 is found in compounds such as Ge2Cl6, and +3 and +1 are found on the surface of oxides, or negative oxidation states in germanides, such as −4 in 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. The oxidation states of the element in these ions are not integers—similar to the ozonides O3.

Hafnium compounds are compounds containing the element hafnium (Hf). Due to the lanthanide contraction, the ionic radius of hafnium(IV) (0.78 ångström) is almost the same as that of zirconium(IV) (0.79 angstroms). Consequently, compounds of hafnium(IV) and zirconium(IV) have very similar chemical and physical properties. Hafnium and zirconium tend to occur together in nature and the similarity of their ionic radii makes their chemical separation rather difficult. Hafnium tends to form inorganic compounds in the oxidation state of +4. Halogens react with it to form hafnium tetrahalides. At higher temperatures, hafnium reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Some compounds of hafnium in lower oxidation states are known.

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