An element whose existence was postulated by Dmitri Mendeleev, germanium was discovered by the German chemist Clemens Winkler in the mineral argyrodite in 1886. The metal took its name for the country of Germany. Today, germanium is primarily obtained from the smelting of zinc ores and is recovered from certain types of coal ash in Russia and China.
Germanium is a lustrous, grayish-white, hard and brittle semi-metallic element that oxidizes slowly in air. Along with silicon, gallium, bismuth, antimony and water, it is one of the few substances that expands as it solidifies from its molten state. Zone refining techniques have led to the production of crystalline germanium that has an impurity of only one part in 1010, making it amongst the purest materials ever obtained.
In 2005, Germanium (with uranium and rhodium) was the first metallic material discovered to become a superconductor in the presence of an extremely strong electromagnetic field.
Applications of Germanium:
- Optics: Germanium oxide (or ‘Germania’) has a high index of refraction and a low optical dispersion, making it especially useful for wide-angle camera lenses, microscopy and for the core part of optical fibres. Germanium is also used in infrared optical glasses that can be readily cut and polished into specialty lenses in cameras; for passive thermal imaging; for hot-spot detection in night vision systems; and for firefighting applications. It is also used in infrared spectroscopes and other optical equipment which require extremely sensitive infrared detectors.
- Electronics: Silicon germanide is an important semiconductor material used in high speed integrated circuits, such as wireless communications devices. Other uses in electronics include phosphors in fluorescent lamps and germanium-based solid-state light-emitting diodes (LEDs).
- Solar Cells: Because germanium and gallium arsenide have very similar lattice constants, germanium substrates can be used to make gallium arsenide solar cells.
- Other Uses: Germanium and germanium oxide, being transparent to infrared radiation, are used in infrared optical instruments and infrared detectors. In sterling silver alloys, it reduces firescale, increases tarnish resistance and increases the alloy's response to precipitation hardening. High purity germanium single crystal detectors can precisely identify radiation sources—for example in airport security. Finally, germanium dioxide is used in catalysts for polymerisation in the production of polyethylene terephthalate (PET), the highly brilliant polyester produced used for PET bottles.