Germanium is a
chemical element
A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substance consisting only of that species. Unlike chemical compounds, chemical elements canno ...
with the
symbol Ge and
atomic number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of ever ...
32. It is lustrous, hard-brittle, grayish-white and similar in appearance to
silicon
Silicon is a chemical element with the 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 ...
. 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
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
in nature.
Because it seldom appears in high concentration, germanium was discovered comparatively late in the
discovery of the elements. Germanium ranks near fiftieth
in relative abundance of the elements in the Earth's crust. In 1869,
Dmitri Mendeleev
Dmitri Ivanovich Mendeleev (sometimes transliterated as Mendeleyev or Mendeleef) ( ; russian: links=no, Дмитрий Иванович Менделеев, tr. , ; 8 February Old_Style_and_New_Style_dates">O.S._27_January.html" ;"title="O ...
predicted its existence and some of its
properties from its position on his
periodic table, and called the element ekasilicon. In 1886,
Clemens Winkler at Freiberg University found the new element, along with
silver
Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
and
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
, in the mineral
argyrodite
Argyrodite is an uncommon silver germanium sulfide mineral with formula Ag8GeS6. The color is iron-black with a purplish tinge, and the luster metallic.
Discovered by Clemens Winkler in 1886, it is of interest as it was described shortly after t ...
. Winkler named the element after his country,
Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwee ...
. Germanium is mined primarily from
sphalerite (the primary ore of
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
), though germanium is also recovered commercially from
silver
Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
,
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
, and
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
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 diode
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
s (LEDs). Germanium compounds are also used for
polymerization
In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many f ...
catalysts and have most recently found use in the production of
nanowires. This element forms a large number of
organogermanium compounds, such as
tetraethylgermanium
Tetraethylgermanium (common name tetraethyl germanium), abbreviated TEG, is an organogermanium compound with the formula ( CH3CH2)4 Ge. Tetraethylgermanium is an important chemical compound used in vapour deposition of germanium which is in a tetr ...
, useful in
organometallic chemistry. Germanium is considered a
technology-critical element.
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
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...
. However, synthetic soluble germanium salts are
nephrotoxic, and synthetic chemically reactive germanium compounds with
halogens and
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...
are irritants and toxins.
History
In his report on ''The Periodic Law of the Chemical Elements'' in 1869, the Russian chemist
Dmitri Mendeleev
Dmitri Ivanovich Mendeleev (sometimes transliterated as Mendeleyev or Mendeleef) ( ; russian: links=no, Дмитрий Иванович Менделеев, tr. , ; 8 February Old_Style_and_New_Style_dates">O.S._27_January.html" ;"title="O ...
predicted the existence of several unknown
chemical element
A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substance consisting only of that species. Unlike chemical compounds, chemical elements canno ...
s, including one that would fill a gap in the
carbon family, located between
silicon
Silicon is a chemical element with the 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 ...
and
tin. 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
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
was discovered and named ''
argyrodite
Argyrodite is an uncommon silver germanium sulfide mineral with formula Ag8GeS6. The color is iron-black with a purplish tinge, and the luster metallic.
Discovered by Clemens Winkler in 1886, it is of interest as it was described shortly after t ...
'' because of its high
silver
Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
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
Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient ti ...
. 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
Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
word, ''
Germania'', for Germany) in honor of his homeland.
Argyrodite proved empirically to be Ag
8GeS
6.
Because this new element showed some similarities with the elements
arsenic
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, b ...
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
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 ...
(), while
Lecoq de Boisbaudran deduced 72.3 by a comparison of the lines in the spark
spectrum
A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...
of the element.
Winkler was able to prepare several new compounds of germanium, including
fluorides,
chlorides,
sulfides
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds la ...
,
dioxide
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of ...
, and
tetraethylgermane (Ge(C
2H
5)
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
Periodicity or periodic may refer to:
Mathematics
* Bott periodicity theorem, addresses Bott periodicity: a modulo-8 recurrence relation in the homotopy groups of classical groups
* Periodic function, a function whose output contains values tha ...
. Here is a comparison between the prediction and Winkler's data:
Until the late 1930s, germanium was thought to be a poorly conducting
metal
A metal (from ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, e ...
.
Germanium did not become economically significant until after 1945 when its properties as an
electronic semiconductor were recognized. During
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, small amounts of germanium were used in some special
electronic devices, mostly
diodes. The first major use was the point-contact
Schottky diode
The Schottky diode (named after the German physicist Walter H. Schottky), also known as Schottky barrier diode or hot-carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage ...
s for
radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...
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
rectifier
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (converting DC to AC) is performed by an inve ...
s.
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 optic communication networks, infrared
night vision systems, and
polymerization
In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many f ...
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
Ton is the name of any one of several units of measure. It has a long history and has acquired several meanings and uses.
Mainly it describes units of weight. Confusion can arise because ''ton'' can mean
* the long ton, which is 2,240 pounds
...
(132
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
) 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
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical f ...
. While silicon could be bought in 1998 for less than $10 per kg,
the price of germanium was almost $800 per kg.
Characteristics
Under
standard conditions, germanium is a brittle, silvery-white, semi-metallic element.
This form constitutes an
allotrope known as ''α-germanium'', which has a metallic luster and a
diamond cubic crystal structure, the same as
diamond
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, b ...
.
While in crystal form, germanium has a displacement threshold energy of
. At pressures above 120
kbar, germanium becomes the allotrope ''β-germanium'' with the same structure as β-
tin.
Like silicon,
gallium,
bismuth,
antimony
Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient ti ...
, and
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
, germanium is one of the few substances that expands as it solidifies (i.e.
freezes) from the molten state.
Germanium is a
semiconductor
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...
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 10
10,
making it one of the purest materials ever obtained.
The first 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
A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit. ...
.
Chemistry
Elemental germanium starts to oxidize slowly in air at around 250 °C, forming
GeO2 . Germanium is insoluble in dilute
acids and
alkalis
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a s ...
but dissolves slowly in hot concentrated sulfuric and nitric acids and reacts violently with molten alkalis to produce
germanate
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.Egon ...
s (). Germanium occurs mostly in the
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
+4 although many +2 compounds are known.
Other oxidation states are rare: +3 is found in compounds such as Ge
2Cl
6, and +3 and +1 are found on the surface of oxides, or negative oxidation states in
germanide A germanide is any binary compound of germanium and a more electropositive element. The composition of most germanides is analogous to that of the corresponding silicides and does not follow formal valence rules. The germanides of alkali and alkalin ...
s, such as −4 in . Germanium cluster anions (
Zintl ions) such as Ge
42−, Ge
94−, Ge
92−,
9)2">Ge9)2sup>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 O
3−.
Two
oxides of germanium are known:
germanium dioxide (, germania) and
germanium monoxide, ().
The dioxide, GeO
2 can be obtained by roasting
germanium disulfide
Germanium disulfide or Germanium(IV) sulfide is the inorganic compound with the formula Ge S2. 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 po ...
(), 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 GeO
2 with Ge metal.
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
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...
light.
Bismuth germanate
Bismuth germanium oxide or bismuth germanate is an inorganic chemical compound of bismuth, germanium and oxygen. Most commonly the term refers to the compound with chemical formula (BGO), with the cubic evlitine crystal structure, used as a sci ...
, Bi
4Ge
3O
12, (BGO) is used as a
scintillator.
Binary compounds with other
chalcogens are also known, such as the di
sulfide
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds la ...
(), di
selenide (), and the
monosulfide (GeS), selenide (GeSe), and
telluride (GeTe).
GeS
2 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
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...
, 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
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
, germanium compounds form salts known as thiogermanates.
Four tetra
halides are known. Under normal conditions GeI
4 is a solid, GeF
4 a gas and the others volatile liquids. For example,
germanium tetrachloride
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 ...
, GeCl
4, 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.
GeCl
4 is used in the production of organogermanium compounds.
All four dihalides are known and in contrast to the tetrahalides are polymeric solids.
Additionally Ge
2Cl
6 and some higher compounds of formula Ge
''n''Cl
2''n''+2 are known.
The unusual compound Ge
6Cl
16 has been prepared that contains the Ge
5Cl
12 unit with a
neopentane structure.
Germane (GeH
4) is a compound similar in structure to
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane ...
. Polygermanes—compounds that are similar to
alkanes—with formula Ge
''n''H
2''n''+2 containing up to five germanium atoms are known.
The germanes are less volatile and less reactive than their corresponding silicon analogues.
GeH
4 reacts with alkali metals in liquid ammonia to form white crystalline MGeH
3 which contain the
GeH3− anion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
.
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 R
4Ge (where R is an
alkyl
In organic chemistry, an alkyl group is an alkane missing one hydrogen.
The term ''alkyl'' is intentionally unspecific to include many possible substitutions.
An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloa ...
) such as
tetramethylgermane () and tetraethylgermane are accessed through the cheapest available germanium precursor
germanium tetrachloride
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 ...
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
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...
applications. Many germanium
reactive intermediates are known:
germyl
Germyl, trihydridogermanate(1-), trihydrogermanide, trihydridogermyl or according to IUPAC Red Book: germanide is an anion containing germanium bounded with three hydrogens, with formula . Germyl is the IUPAC term for the – group. For less elect ...
free radicals, germylenes (similar to
carbene
In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms.
The term "carbene" m ...
s), and germynes (similar to
carbynes). 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.
Isotopes
Germanium occurs in 5 natural
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass num ...
s: , , , , and . Of these, is very slightly radioactive, decaying by
double beta decay with a
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ...
of . is the most common isotope, having a
natural abundance of approximately 36%. is the least common with a natural abundance of approximately 7%.
When bombarded with alpha particles, the isotope will generate stable , releasing high energy electrons in the process.
Because of this, it is used in combination with
radon
Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colourless, odourless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains th ...
for
nuclear batteries.
[Perreault, Bruce A]
"Alpha Fusion Electrical Energy Valve"
US Patent 7800286, issued September 21, 2010.
At least 27
radioisotopes have also been synthesized, ranging in atomic mass from 58 to 89. The most stable of these is , decaying by
electron capture
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. ...
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
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
, and decay by
delayed
proton emission.
through isotopes also exhibit minor
delayed
neutron emission decay paths.
Occurrence
Germanium is created by
stellar nucleosynthesis
Stellar nucleosynthesis is the creation (nucleosynthesis) of chemical elements by nuclear fusion reactions within stars. Stellar nucleosynthesis has occurred since the original creation of hydrogen, helium and lithium during the Big Bang. A ...
, mostly by the
s-process in
asymptotic giant branch stars. The s-process is a slow
neutron
The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the atomic nucleus, nuclei of atoms. Since protons and ...
capture of lighter elements inside pulsating
red giant stars.
Germanium has been detected in some of the most distant stars and in the atmosphere of Jupiter.
Germanium's abundance
in the Earth's crust is approximately 1.6
ppm.
Only a few minerals like
argyrodite
Argyrodite is an uncommon silver germanium sulfide mineral with formula Ag8GeS6. The color is iron-black with a purplish tinge, and the luster metallic.
Discovered by Clemens Winkler in 1886, it is of interest as it was described shortly after t ...
,
briartite,
germanite
Germanite is a rare copper iron germanium sulfide mineral, Cu26Fe4Ge4S32. It was first discovered in 1922, and named for its germanium content. It is only a minor source of this important semiconductor element, which is mainly derived from the p ...
,
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
Victor Moritz Goldschmidt (27 January 1888 in Zürich – 20 March 1947 in Oslo) was a Norwegian mineralogist considered (together with Vladimir Vernadsky) to be the founder of modern geochemistry and crystal chemistry, developer of the Goldsch ...
during a broad survey for germanium deposits.
The highest concentration ever found was in
Hartley
Hartley may refer to:
Places Australia
*Hartley, New South Wales
* Hartley, South Australia
** Electoral district of Hartley, a state electoral district
Canada
*Hartley Bay, British Columbia
United Kingdom
* Hartley, Cumbria
* Hartley, Pl ...
coal ash with as much as 1.6% germanium.
The coal deposits near
Xilinhaote,
Inner Mongolia
Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of the People's Republic of China. Its border includes most of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for a ...
, contain an estimated 1600
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s of germanium.
Production
About 118
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s 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
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
ores where it is concentrated in amounts as great as 0.3%, especially from low-temperature sediment-hosted, massive
Zn–
Pb–
Cu(–
Ba) deposits and carbonate-hosted Zn–Pb deposits. 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. In 2007 35% of the demand was met by recycled germanium.
While it is produced mainly from
sphalerite, it is also found in
silver
Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
,
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
, and
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
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.
Russia's deposits are located in the far east of
Sakhalin
Sakhalin ( rus, Сахали́н, r=Sakhalín, p=səxɐˈlʲin; ja, 樺太 ''Karafuto''; zh, c=, p=Kùyèdǎo, s=库页岛, t=庫頁島; Manchu: ᠰᠠᡥᠠᠯᡳᠶᠠᠨ, ''Sahaliyan''; Orok: Бугата на̄, ''Bugata nā''; Nivkh ...
Island, and northeast of
Vladivostok. The deposits in China are located mainly in the
lignite
Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...
mines near
Lincang
Lincang () is a prefecture-level city located in the southwest of Yunnan province, People's Republic of China.
History
Lincang was previously called Baihuai during the Shang dynasty.
On December 26, 2003, the state council approved the cance ...
,
Yunnan
Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the ...
; coal is also mined near
Xilinhaote,
Inner Mongolia
Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of the People's Republic of China. Its border includes most of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for a ...
.
The ore concentrates are mostly
sulfidic; they are converted to the
oxides by heating under air in a process known as
roasting:
: GeS
2 + 3 O
2 → GeO
2 + 2 SO
2
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 Waelz process is a method of recovering zinc and other relatively low boiling point metals from metallurgical waste (typically EAF flue dust) and other recycled materials using a rotary kiln (''waelz kiln'').
The zinc enriched product is referr ...
, the residing Waelz oxide is leached a second time. The
dioxide
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of ...
is obtained as precipitate and converted with
chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
gas or hydrochloric acid to
germanium tetrachloride
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 ...
, which has a low boiling point and can be isolated by distillation:
: GeO
2 + 4 HCl → GeCl
4 + 2 H
2O
: GeO
2 + 2 Cl
2 → GeCl
4 + O
2
Germanium tetrachloride is either hydrolyzed to the oxide (GeO
2) or purified by fractional distillation and then hydrolyzed.
The highly pure GeO
2 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:
: GeO
2 + 2 H
2 → Ge + 2 H
2O
The germanium for steel production and other industrial processes is normally reduced using carbon:
: GeO
2 + C → Ge + CO
2
Applications
The major end uses for germanium in 2007, worldwide, were estimated to be: 35% for
fiber-optics, 30%
infrared optics, 15%
polymerization
In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many f ...
catalysts, and 15% electronics and solar electric applications.
The remaining 5% went into such uses as phosphors, metallurgy, and chemotherapy.
Optics
The notable properties of
germania (GeO
2) are its high
index of refraction and its low
optical dispersion. These make it especially useful for
wide-angle camera lens
In photography and cinematography, a wide-angle lens refers to a lens whose focal length is substantially smaller than the focal length of a normal lens for a given film plane. This type of lens allows more of the scene to be included in the p ...
es,
microscopy, and the core part of
optical fiber
An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass ( silica) or plastic to a diameter slightly thicker than that of a human hair
Hair is a protein filament that grows ...
s.
It has replaced
titania as the
dopant
A dopant, also called a doping agent, is a trace of impurity element that is introduced into a chemical material to alter its original electrical or optical properties. The amount of dopant necessary to cause changes is typically very low. Whe ...
for silica fiber, eliminating the subsequent heat treatment that made the fibers brittle. 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
A phase change material (PCM) is a substance which releases/absorbs sufficient energy at phase transition to provide useful heat or cooling. Generally the transition will be from one of the first two fundamental states of matter - solid and li ...
used for its optic properties, such as that used in
rewritable DVDs.
Because germanium is transparent in the infrared wavelengths, it is an important
infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...
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
The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Un ...
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
In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium.
The refractive index determines how much the path of light is bent, ...
(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.
Electronics
Germanium can be alloyed with
silicon
Silicon is a chemical element with the 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 ...
, 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. Silicon-germanium is beginning to replace
gallium arsenide (GaAs) in wireless communications devices.
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. 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
phosphors in
fluorescent lamp
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet, ult ...
s
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
Rock and roll (often written as rock & roll, rock 'n' roll, or rock 'n roll) is a genre of popular music that evolved in the United States during the late 1940s and early 1950s. It originated from African-American music such as jazz, rhythm ...
era, most notably the
Dallas Arbiter Fuzz Face.
Other uses
Germanium dioxide is also used in
catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
s for
polymerization
In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many f ...
in the production of
polyethylene terephthalate (PET).
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 (SiO
2) and germanium dioxide (GeO
2), the silica stationary phase in some
gas chromatography columns can be replaced by GeO
2.
In recent years germanium has seen increasing use in precious metal alloys. In
sterling silver alloys, for instance, it reduces
firescale
Firestain is a layer of oxides that is visible on the surface of objects made of metal alloys containing copper when the object is heated, as by a jeweler heating a ring to apply solder during a repair. On copper-containing alloys of gold or of ...
, 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
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. Crystals of high purity germanium are used in detectors for
gamma spectroscopy
Gamma-ray spectroscopy is the quantitative study of the energy spectra of gamma-ray sources, such as in the nuclear industry, geochemical investigation, and astrophysics.
Most radioactive sources produce gamma rays, which are of various energie ...
and the search for
dark matter
Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ...
. Germanium crystals are also used in X-ray spectrometers for the determination of phosphorus, chlorine and sulfur.
Germanium is emerging as an important material for
spintronics
Spintronics (a portmanteau meaning spin transport electronics), also known as spin electronics, is the study of the intrinsic spin of the electron and its associated magnetic moment, in addition to its fundamental electronic charge, in solid- ...
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
coherence time
For an electromagnetic wave, the coherence time is the time over which a propagating wave (especially a laser or maser beam) may be considered coherent, meaning that its phase is, on average, predictable.
In long-distance transmission systems ...
s.
Germanium and health
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
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...
aceous 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).
Germanium supplements, made from both organic and inorganic germanium, have been marketed as an
alternative medicine capable of treating
leukemia
Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
and
lung cancer
Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung. Lung carcinomas derive from transformed, mali ...
.
There is, however, no
medical evidence of benefit; some evidence suggests that such supplements are actively harmful.
U.S. Food and Drug Administration 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
Fatty liver disease (FLD), also known as hepatic steatosis, is a condition where excess fat builds up in the liver. Often there are no or few symptoms. Occasionally there may be tiredness or pain in the upper right side of the abdomen. Complica ...
, 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
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
s, but have toxic effects against certain
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
.
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 chloride and
germane (GeH
4) are a liquid and gas, respectively, that can be very irritating to the eyes, skin, lungs, and throat.
See also
*
Germanene
Germanene is a material made up of a single layer of germanium atoms. The material is created in a process similar to that of silicene and graphene, in which high vacuum and high temperature are used to deposit a layer of germanium atoms on a subs ...
* Vitrain
* History of the transistor
Notes
References
External links
Germaniumat ''The Periodic Table of Videos'' (University of Nottingham)
{{Authority control
Germanium,
Chemical elements
Metalloids
Infrared sensor materials
Optical materials
Group IV semiconductors
Chemical elements predicted by Dmitri Mendeleev
Materials that expand upon freezing
Chemical elements with diamond cubic structure