32
  Ge  
72.610000
Germanium

Name: Germanium
Symbol: Ge
Atomic Number: 32
Atomic Weight: 72.610000
Family: Metalloids
CAS RN: 7440-56-4
Description: A greyish white metalloid (semi-conductor).
State (25C): Solid
Oxidation states: +2, +4

Molar Volume: 13.57 cm3/mole
Valence Electrons: 4p2

Boiling Point:  3103K, 2830C, 5126F
Melting Point:
1210.55K, 937.4C, 1719.3F
Electrons Energy Level: 2, 8, 18, 4
Isotopes: 20 + 5 Stable
Heat of Vaporization: 330.9 kJ/mol
Heat of Fusion: 36.94 kJ/mol
Density: 5.323 g/cm3 @ 300K
Specific Heat: 0.32 J/gK
Atomic Radius: 1.52
Ionic Radius: 0.53
Electronegativity: 2.01 (Pauling); 2.02 (Allrod Rochow)
Vapor Pressure: 0.0000746 Pa @ 937.4C
Like Silicon, Germanium is used in the manufacture of semi-conductor devices. Unlike Silicon, it is rather rare (only about 1 part in 10 million parts in the earth's crust). The metalloid was one of the elements predicted by Mendeleev in 1871 (ekasilicon) to fill out his periodic table and was discovered in 1886 by Winkler.

The physical and chemical properties of Germanium closely parallel those of silicon.  Although it forms a compound, Germanium Dioxide, just like Silicon, it is generally extracted from the by-products of Zinc refining.

This is a lustrous, hard, silver-white metalloid that is chemically similar to Tin.   Germanium forms a large number of organometallic compounds and is an important semiconductor material used in transistors.

First proposed to exist by Dmitri Mendeleyev in 1871 based on gaps in his newly created Periodic Table of Elements, Germanium was discovered by the German chemist Clemens Winkler in the mineral Srgyrodite (Ag8GeS6) in 1886.   Today, Germanium is primarily obtained from the smelting of Zinc ores and from the byproducts of burning certain types of coal.

6
C
12.02
14
Si
28.08
32
Ge
72.15
50
Sn
118.7
82
Pb
207.2
114
Uuq
285.0

  1s2 2s2p6 3s2p6d10 4s2p2

History

In 1871 Germanium (Latin Germania for Germany) was one of the elements that Dmitri Mendeleev predicted to exist as a missing analogue of the Silicon Group (Mendeleev called it "ekasilicon").  The existence of this element was proven by Clemens Winkler in 1886.  This discovery was an important confirmation of Mendeleev's idea of element periodicity.

Property Ekasilicon Germanium
Atomic Mass 72 72.59
Density (g/cm) 5.5 5.35
Melting Point (C) High 947
Color gray gray

The development of the Germanium transistor 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 rectifiers.  Silicon has superior electrical properties, but requires much higher purity samples—a purity which could not be commercially achieved in the early days.  Meanwhile, demand for Germanium in fiber optics communication networks, infrared night vision systems, and polymerization catalysts increased dramatically.  These end uses represented 85% of worldwide Germanium consumption for 2000.

Characteristics

Germanium is a hard, grayish-white element that has a metallic luster and the same crystal structure as diamond.  In addition, it is important to note that germanium is a semiconductor, with electrical properties between those of a metal and an insulator.   In its pure state, this metalloid is crystalline, brittle and retains its luster in air at room temperature.  Zone refining techniques have led to the production of crystalline Germanium for semicondictors that have an impurity of only one part in 1010.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p2

Occurrence

This element is found in Argyrodite (Sulfide of Germanium and Silver); coal; Germanite; Zinc Ores; and other minerals.

Germanium is obtained commercially from zinc ore processing smelter dust and from the combustion by-products of certain coals. A large reserve of this element is therefore in coal sources.

This metalloid can be extracted from other metals by fractional distillation of its volatile Tetrachloride.  This technique permits the production of ultra-high purity germanium.

Applications

Unlike most semiconductors, Germanium has a small band gap, allowing it to efficiently respond to infrared light.  It is therefore used in infrared spectroscopes and other optical equipment which require extremely sensitive infrared detectors. Its oxide's index of refraction and dispersion properties make Germanium useful in wide-angle camera lenses and in microscope objective lenses.

Germanium transistors are still used in some stompboxes by musicians who wish to reproduce the distinctive tonal character of the "fuzz-tone" from the early rock and roll era.  Vintage stompboxes known to contain Germanium transistors have shown marked increases in collector value for this reason alone.

Germanium is an highly important infra-red optical material and can be readily cut and polished into lenses and windows.  It is used particularly as the front optic in thermal imaging cameras working in the 8 to 14 micron wavelength range for passive thermal imaging and for hot-spot detection in military and fire fighting applications.  The material has a very high refractive index (4.0) and so needs to be anti-reflection coated.   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 rough treatment.

The alloy Silicon Germanide (commonly referred to as "Silicon-Germanium", or SiGe) is rapidly becoming an important semiconductor material, for use in high speed integrated circuits. Circuits utilizing the properties of Si-SiGe junctions can be much faster than those using silicon alone.

Certain compounds of Germanium have low toxicity to mammals, but have toxic effects against certain bacteria.  This property makes these compounds useful as chemotherapeutic agents.

Germanium is useful for single crystal neutron or synchrotron X-ray monochromator for beamlines.  The reflectivity has advantages over Silicon in neutron and High energy X-ray applications.

While Germanium has been claimed as an attractive nutritional supply, able to cure cancer and AIDS, FDA research has concluded that the offered supplements "present potential human health hazard".

In recent years Germanium has seen increasing use in precious metal alloys.  In sterling silver alloys, for instance, it has been found to reduce firescale,   increase tarnish resistance, and increase the alloy's response to precipitation hardening.

Value

In 1998 the cost of Germanium was about $3 pe gram.  The yearend price for zone-refined germanium has (generally) decreased since then:

2000.....$1,150 per kilogram (or $1.15 per gram) 2001........$890 per kilogram (or $0.89 per gram) 2002........$620 per kilogram (or $0.62 per gram) 2003........$380 per kilogram (or $0.38 per gram) 2004........$600 per kilogram (or $0.60 per gram) 2005........$610 per kilogram (or $0.61 per gram) 2006........$720 per kilogram (or $0.72 per gram) 2007........$460 per kilogram (or $0.46 per gram)

Compounds

Some inorganic Germanium compounds include Germane or Germanium Tetrahydride (GeH4), Germanium Tetrachloride (GeCl4), and Germanium Dioxide (Germania) (GeO2).   Some organic compounds of Germanium include Tetramethylgermane or Tetramethyl Germanium, (Ge(CH3)4), and Tetraethylgermane or Tetraethyl Germanium, (Ge(C2H5)4).  Recently a new organogermanium compound Isobutylgermane ((CH3)2CHCH2GeH3), was reported as the less hazardous liquid substitute for toxic Germane gas in semiconductor applications.

Isotopes

atom.gif (700 bytes)

Isotope Atomic Mass Half-Life
Ge58 57.991  
Ge59 58.982  
Ge60 59.97  
Ge61 60.964 40 ms
Ge62 61.955  
Ge63 62.95 95 ms
Ge64 63.942 63.7 seconds
Ge65 64.939 30.9 seconds
Ge66 65.9338 2.26 hours
Ge67 66.9327 18.9 minutes
Ge68 67.9281 270.8 days
Ge69 68.928 39.05 hours
Ge70 69.9243 Stable
Ge71 70.925 11.43 days
Ge72 71.9221 Stable
Ge73 72.9235 Stable
Ge74 73.9212 Stable
Ge75 74.9229 82.78 minutes
Ge76 75.9214 Stable
Ge77 76.9236 11.3 hours
Ge78 77.9229 88 minutes
Ge79 78.9254 18.98 seconds
Ge80 79.9254 29.5 seconds
Ge81 80.929 7.6 seconds
Ge82 81.93 4.6 seconds
Ge83 82.935 1.85 seconds
Ge84 83.937 947 ms
Ge85 84.943 535 ms
Ge86 85.946 >150 ns
Ge87    
Ge88    
Ge89    

atom.gif (700 bytes)

Germanium Data

Atomic Radius (): 1.52
Atomic Volume cm3/mol : 13.6cm3/mol
Covalent Radius: 1.22
Crystal Structure: Cubic face centered
Ionic Radius: 0.53

Chemical Properties

Electrochemical Equivalents: 0.6771 g/amp-hr
Electron Work Function: 5eV
Electronegativity: 2.01 (Pauling); 2.02 (Allrod Rochow)
Heat of Fusion: 36.94 kJ/mol
Incompatibilities: Acids
First Ionization Potential: 7.899
Second Ionization Potential: 15.934
Third Ionization Potential: 34.22
Valence Electron Potential: 109
Ionization Energy (eV): 7.900 eV

Physical Properties

Atomic Mass Average: 72.61
Boiling Point: 3103K, 2830C, 5126F
Melting Point: 1210.55K, 937.4C, 1719.3F
Heat of Vaporization: 330.9 kJ/mol
Coefficient of Lineal Thermal Expansion/K-1: 5.57E-6
Electrical Conductivity: 1.45E-8 106/cm
Thermal Conductivity: 0.599 W/cmK
Density: 5.323 g/cm3 @ 300K
Enthalpy of Atomization: 376.6 kJ/mole @ 25C
Enthalpy of Fusion: 34.7 kJ/mole
Enthalpy of Vaporization: 334.3 kJ/mole
Flammability Class: Combustible Solid, fine dust is easily ignited
Molar Volume: 13.57 cm3/mole
Optical Refractive Index: unknown
Relative Gas Density (Air=1): unknown
Specific Heat: 0.32 J/gK
Vapor Pressure: 0.0000746 Pa @ 937.4C
Estimated Crustal Abundance: 1.5 milligrams per kilogram
Estimated Oceanic Abundance: 510-5 milligrams per liter


(L. Germania, Germany) Predicted by Mendeleev in 1871 as ekasilicon, and discovered by Winkler in 1886. The metal is found in argyrodite, a sulfide of germanium and silver; in germanite, which contains 8% of the element; in zinc ores; in coal; and in other minerals. The element is frequently obtained commercially from the dusts of smelters processing zinc ores, and has been recovered from the by-products of combustion of certain coals. Its presence in coal insures a large reserve of the element in the years to come. Germanium can be separated from other metals by fractional distillation of its volatile tetrachloride. The techniques permit the production of germanium of ultra-high purity. The element is a gray-white metalloid, and in its pure state is crystalline and brittle, retaining its luster in air at room temperature. It is a very important semiconductor material. Zone-refining techniques have led to production of crystalline germanium for semiconductor use with an impurity of only one part in 1010. Doped with arsenic, gallium, or other elements, it is used as a transistor element in thousands of electronic applications. Its application as a semiconductor element now provides the largest use for germanium. Germanium is also finding many other applications including use as an alloying agent, as a phosphor in fluorescent lamps, and as a catalyst. Germanium and germanium oxide are transparent to the infrared and are used in infrared spectroscopes and other optical equipment, including extremely sensitive infrared detectors. Germanium oxide's high index of refraction and dispersion has made it useful as a component of glasses used in wide-angle camera lenses and microscope objectives. The field of organogermanium chemistry is becoming increasingly important. Certain germanium compounds have a low mammalian toxicity, but a marked activity against certain bacteria, which makes them of interest as chemotherapeutic agents. The cost of germanium is about $3/g.

Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond