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Supplier Data - Germanium (Ge) (Goodfellow)

Background

Germanium (Ge) is a silvery white brittle metalloid member of the carbon group of elements, its physical properties being similar to those of silicon, the element which precedes it in the group.

Discovered in 1886 by C.A. Winkler at Freiberg, Germany.

Occurrence and Abundance

Other elements within the carbon group are relatively common, but Germanium is found only in trace amounts in some coals and as a minor component in some ores, the principle one being argyrodite, a double sulphide of silver and Germanium (the mineral from which germanium was first isolated). It has an abundance within the Earth’s crust of 1.8 ppm.

Extraction

The element Germanium is produced by reduction of the oxide, ultra-high purity material being obtained by zone refining (a process in which the element is formed into a rod which is then heated at one end to produce a narrow molten zone. The heater is moved along the length of the rod so that the molten zone travels from one end of the rod to the other. Impurities are more soluble in the molten metal than in the solid and thus concentrate in the liquid zone as it moves to one end of the rod).

Applications

Germanium is stable in air and water and is unaffected by alkalis and acids, with the exception of nitric acid. It is a poor conductor of electricity but has exceptional properties as a semiconductor material and it is in this area where germanium is primarily used.

However, other applications for Germanium include its use as an alloying element in the production of specific alloys and as an addition to glass in the manufacture of infrared devices.

Key Properties

The key properties of Germanium are tabulated below.

Table 1. Key properties

Atomic Properties
Atomic number 32
Atomic radius - Goldschmidt ( nm ) 0.139
Atomic weight ( amu ) 72.59
Crystal structure Diamond
Electronic structure Ar 3d10 4s2 4p2
Photo-electric work function ( eV ) 4.8
Thermal neutron absorption cross-section ( Barns ) 2.3
Valences shown 2, 4
Ionisation Potential No. eV
1 7.90
2 15.93
3 34.22
4 45.7
5 93.5
Natural Isotope Distribution Mass No. %
70 20.5
72 27.4
73 7.8
74 36.5
76 7.8
Electrical Properties
Electrical resistivity @ 22 °C ( µOhm.cm ) 46x106
Thermal emf against Pt (cold 0 °C - hot 100 °C) ( mV ) +33.9
Mechanical Properties
Material condition Polycrystalline
Bulk modulus ( GPa ) 73.9
Hardness - Mohs 6.25
Poisson’s ratio 0.32 0.32
Tensile modulus ( GPa ) 79.9 79.9
Physical Properties
Boiling point ( °C ) 2830
Density @ 20 °C ( g.cm-3 ) 5.32
Melting point (°C ) 937.4
Thermal Properties
Coefficient of thermal expansion @ 0-100 °C ( x10-6 K-1 ) 5.75
Latent heat of evaporation ( J.g-1 ) 4516
Latent heat of fusion ( J.g-1 ) 465
Specific heat @ 25 °C ( J.K-1.kg-1 ) 322
Thermal conductivity @ 0-100 °C ( W.m-1.K-1 ) 60.2

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