Germanium
|
 |
Atomic Number: |
32 |
|
Melting
Point: |
938.25 ºC |
| Atomic Symbol: |
Ge |
|
Boiling
Point: |
2833 ºC |
| Atomic Weight: |
72.59
amu |
|
Density: |
5323
kg/m 3
|
| Atomic
Radius: |
122.5 pm
|
|
Oxidation States: |
4, 2 |
| Covalent Radius: |
122 pm |
|
Electron
Configuration: |
[Ar]4s23d104p2 |
| van der Waals
Radius: |
-- |
|
State of Matter: |
solid |
History
(Latin Germania: Germany) Mendeleev predicted the existence of
Germanium in 1871 as ekasilicon, and the element was discovered by Winkler in
1886.
Properties
The element is a gray-white metalloid. In pure state, the element is
crystalline and brittle, retaining its luster in air at room temperature. It is
a very important semiconductor. Zone-refining techniques have led to production
of crystalline germanium for semiconductor use with an impurity of only one part
in 1010.
Sources
The metal is found in argyrodite, a sulfide of germanium and
silver; germanite,
which contains 8 percent of the element;
zinc ores, coal,
and other minerals.
The element is commercially obtained from the dusts of smelters processing
zinc ores, as well as recovered from combustion by-products of certain coals. A
large reserve of the elements for future uses in insured in coal sources.
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.
Uses
The development of the germanium transistor opened the door to countless
applications of solid-state electronics. 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. 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.
Germanium transistors are still used in electric guitar amplifiers by musicians
who wish to reproduce the distinctive character of amplifiers from the early
Rock and roll era. The 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.
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. The high index of refraction and dispersion
properties of its oxide's have made germanium useful as a component of
wide-angle camera lenses and microscope objectives.
The field of organo-germanium chemistry is becoming increasingly important.
Certain germanium compounds have a low mammalian toxicity, but a marked activity
against certain bacteria, which makes them useful as chemotherapeutic agents.
The alloy silicon germanide (SiGe) is rapidly becoming an
important semiconductor material, for use in high speed
integrated circuits. Circuits utilising the properties of
Si-SiGe junctions can be much faster than those using silicon
alone.
Isotopes
Germanium has a total of twenty-five isotopes of which only five are stable.
Hazards
As a solid, this product does not present special health hazards. Conditions
and work practices which generate dust or fumes should be avoided or controlled.