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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 or a nonmetal in the carbon group that is chemically similar to silicon. 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 50th 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 Germany, his country of birth. 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 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 . This element forms a large number of organogermanium compounds, such as tetraethylgermanium, useful in organometallic chemistry.
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 and hydrogen are irritants and toxins.
In mid-1885, at a mine near Freiberg, Saxony, a new mineral was discovered and named argyrodite because of its high silver content. 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. 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. 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). 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. With further material from 500 kg of ore from the mines in Saxony, Winkler confirmed the chemical properties of the new element in 1887. He also determined an atomic weight of 72.32 by analyzing pure germanium tetrachloride (), while Lecoq de Boisbaudran deduced 72.3 by a comparison of the lines in the spark spectrum of the element.
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 Periodic table. Here is a comparison between the prediction and Winkler's data:
| 72.63 |
| 5.35 |
| 947 |
| gray |
| refractory dioxide |
| 4.7 |
| feebly basic |
| 86 (GeCl4) |
| 1.9 |
Until the late 1930s, germanium was thought to be a poorly conducting metal. Germanium did not become economically significant until after 1945 when its properties as an electronics semiconductor were recognized. During World War II, small amounts of germanium were used in some special electronics, mostly . The first major use was the point-contact for radar pulse detection during the War. The first silicon–germanium alloys were obtained in 1955. 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 .
The development of the germanium transistor in 1948 opened the door to countless applications of solid state electronics. 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 . 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.
Meanwhile, the demand for germanium for fiber optics 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 Short 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.
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,
making it one of the purest materials ever obtained.
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.
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.
Two of germanium are known: germanium dioxide (, germania) and germanium monoxide, (). The dioxide, GeO2, can be obtained by roasting germanium disulfide (), and is a white powder that is only slightly soluble in water but reacts with alkalis to form . 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. Bismuth germanate, Bi4Ge3O12 (BGO), is used as a scintillator.
with other are also known, such as the disulfide () and diselenide (), 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. 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.
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 nCl2 n+2 are known. The unusual compound Ge6Cl16 has been prepared that contains the Ge5Cl12 unit with a neopentane structure.
Germane (GeH4) is a compound similar in structure to methane. Polygermanes—compounds that are similar to —with formula Ge nH2 n+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 germyl anion. The germanium hydrohalides with one, two and three halogen atoms are colorless reactive liquids.
The first organogermanium compound was synthesized by Winkler in 1887; the reaction of germanium tetrachloride with diethylzinc yielded tetraethylgermane (). Organogermanes of the type R4Ge (where R is an alkyl) such as tetramethylgermane () and tetraethylgermane are accessed through the cheapest available germanium precursor germanium tetrachloride and alkyl nucleophiles. Organic germanium hydrides such as isobutylgermane () 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: -yl , (similar to ), and germynes (similar to ). The organogermanium compound Propagermanium 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.
At least 27 have also been synthesized, ranging in atomic mass from 58 to 89. The most stable of these is , decaying by electron capture with a half-life of ays. The least stable is , with a half-life of . While most of germanium's radioisotopes decay by beta decay, and decay by delayed proton emission. through isotopes also exhibit minor Beta decay delayed neutron emission decay paths.
Germanium's abundance in the Earth's crust is approximately 1.6 ppm. Only a few minerals like argyrodite, briartite, germanite, renierite and sphalerite contain appreciable amounts of germanium. Only few of them (especially germanite) are, very rarely, found in mineable amounts. 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. 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 of germanium.
| 1,400 |
| 1,250 |
| 890 |
| 620 |
| 380 |
| 600 |
| 660 |
| 880 |
| 1,240 |
| 1,490 |
| 950 |
| 940 |
| 1,625 |
| 1,680 |
| 1,875 |
| 1,900 |
| 1,760 |
| 950 |
| 1,358 |
| 1,300 |
| 1,240 |
| 1,000 |
The ore concentrates are mostly sulfide; they are converted to the by heating under air in a process known as roasting:
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:
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:
The germanium for steel production and other industrial processes is normally reduced using carbon:
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 micrometre range for passive thermal imaging and for hot-spot detection in military, mobile night vision, and fire fighting applications. It is used in infrared and other optical equipment that require extremely sensitive thermography. 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.
High efficiency 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 . 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. 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. Other uses in electronics include in and solid-state light-emitting diodes (LEDs). Germanium transistors are still used in some by musicians who wish to reproduce the distinctive tonal character of the "fuzz"-tone from the early rock and roll era, most notably the Fuzz Face.
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.
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. 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.
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.
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. Germanium is useful for monochromators for 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. Crystals of high purity germanium are used in detectors for gamma spectroscopy and the search for dark matter. 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 and more recently donor electron spins in germanium has been shown to have very long .
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. (2025). 9780944235713, American Cancer Society. ISBN 9780944235713 U.S. Food and Drug Administration (FDA) research has concluded that inorganic germanium, when used as a nutritional supplement, "presents potential human health hazard".
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.
Certain compounds of germanium have low toxicity to , but have toxic effects against certain bacterium.
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