Germanium

Germanium was discovered in 1886 by the German chemist Clemens Winkler. Almost ten years earlier, the Russian chemist Dmitri Ivanovich Mendeleev had predicted the existence of germanium, which would be homologous to silicon. Mendeleev called the then undiscovered element Eka-silicon. Winkler gave the element the name Germanium.

The poor availability of the element made further investigations difficult. Moreover, no technical applications were initially found for the rare non-metallic element.

Germanium only gained economic significance after 1945, when its properties as a semiconductor for electronics were recognized.

Many other substances are now also used as semiconductors, but germanium remains of great importance for the manufacture of transistors and components for devices such as rectifiers and photo cells.

About half of the germanium produced is used in fiber optics. Germanium dioxide is used to improve light transmission. Germanium is indispensable for high-speed internet, telecommunications, and data centers.

The second most important application, with a share of about 30 percent, is infrared optics (IR) and thermal imaging. Germanium lenses and windows are used in military night vision devices and thermal cameras. In the automotive industry, germanium is employed in driver assistance systems as well as in satellite imaging.

The use of germanium in semiconductors and electronics remains relevant but is declining. It is used in high-speed transistors, diodes, and solar cells. Silicon-germanium alloys (SiGe) improve the performance of 5G and mobile communication chips.

Germanium is obtained as a byproduct during the processing of zinc and coal. About 80 percent of the world’s produced germanium comes from zinc ore processing. The most important mineral for germanium extraction from zinc is sphalerite, the most significant zinc ore.

China is a major producer of germanium from coal sources. During coal combustion, germanium accumulates in fly ash, from which it is then recovered.

After China, which dominates global germanium production with 60 to 70 percent, Russia and Canada are other production countries.

The largest germanium producer in the world is the Chinese company Yunnan Germanium Industry, headquartered in Kunming, Yunnan Province.

Silicon or gallium arsenide replace germanium in certain electronic applications.

Some metal compounds can be substituted in high-frequency electronic applications and in some LED applications.

Chalcogenide glass has been used as a substitute for germanium metal in infrared applications.

Antimony and titanium are used as polymerization catalysts.

Elemental Germanium

Germanium is located in the periodic table among the metalloids but is classified as a semiconductor according to newer definitions. Elemental germanium is very brittle and highly stable in air at room temperature. Only when strongly heated (glowing) in an oxygen atmosphere does it oxidize to germanium(IV) oxide (GeO₂). GeO₂ is dimorphic and transforms at 1033 °C from the rutile modification (coordination number CN = 6) into the β-quartz structure (CN = 4). In powdered form, it is a flammable solid and can be easily ignited by a brief exposure to an ignition source and continues burning even after the source is removed. The ignition risk increases with finer particle size. In compact form, germanium is non-flammable.

Germanium exhibits oxidation states of +2 and +4, with germanium(IV) compounds being the most stable. It is resistant to attack by hydrochloric acid, potassium hydroxide, and diluted sulfuric acid. However, it dissolves in alkaline hydrogen peroxide solutions, concentrated hot sulfuric acid, and concentrated nitric acid, forming germanium dioxide hydrate.

According to its position in the periodic table, germanium’s chemical properties lie between those of silicon and tin.

Germanium is one of the few substances that exhibits the property of density anomaly: its density in the solid state is lower than in the liquid state. Its bandgap at room temperature is approximately 0,67 eV.