Germanium
.
Germanium is a
chemical element in the
periodic table that has the symbol
Ge and
atomic number 32. 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.
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
lustre in air at room temperature.
Zone refining techniques have led to the production of crystalline germanium for
semiconductors that have an impurity of only one part in 10
10.
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/cm3) | 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.
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.
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 utilising the properties of Si-SiGe junctions can be much faster than those using silicon alone.
Other uses:
*
Alloying agent;
* Phosphor in
fluorescent lamps
*
catalyst* High purity germanium single crystal detectors can precisely identify radiation sources (e.g. for airport security)
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 even cancer and
AIDS,
FDA research has concluded that the offered supplements "present potential human health hazard".
This element is found in
argyrodite (
sulfide of germanium and
silver);
coal;
germanite;
zinc ores; and other
minerals. See also
:Category:Germanium mineralsGermanium 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.
In
1997 the cost of germanium was about
US$3 per
gram. The yearend price for germanium in
2000 was $1,150 per
kilogram (or $1.15 per gram).
Some germanium compounds include
Germanium tetrahydride (GeH
4),
Germanium tetrachloride (GeCl
4),and
Germanium dioxide (germania) (GeO
2).
See also
:Category:Germanium compounds*
Los Alamos National Laboratory – Germanium*
WebElements.com – Germanium
