Germanium (Ge)
Germanium (Ge) is a hard, brittle, grayish-white metal with the atomic number 32 and is classified in Group IVA of the periodic table. It is the thirty-sixth most abundant element in the Earth's crust, occurring in small quantities within ores of silver, copper, and zinc, with significant deposits found in Germany. Germanium is especially notable for its role in the electronics industry, primarily as a key material in the manufacture of semiconductor devices like transistors, diodes, and solar cells. Its unique crystalline structure resembles that of silicon and allows it to exhibit semiconductor properties, which can be enhanced through a process called doping.
Discovered in 1886 by German chemist Clemens Winkler, germanium has since been extensively studied and utilized for its electronic properties. The metal's conductivity can be improved with the addition of specific elements, enabling its widespread application in technology. Additionally, germanium is employed in various optical devices, including lenses and prisms, as well as in dental materials and high-refractive index optical glasses. Its extraction involves sophisticated processes from zinc sulfide ores and coal, resulting in highly pure germanium essential for modern electronic applications.
Germanium (Ge)
Where Found
Germanium is the thirty-sixth most abundant element in the Earth’s crust, with an average abundance of about 7 grams per metric ton. It occurs in small quantities in ores of silver, such as argyrodite, as well as in ores of copper and zinc, and is found most abundantly in Germany.
Primary Uses
Germanium is of central importance in the manufacture of semiconductor materials and devices, especially transistors. It is also used in a variety of optical devices.
Technical Definition
Germanium, symbol Ge, is located in Group IVA of the periodic table, having atomic number 32 and an atomic weight of 72.59. It is a hard, brittle, grayish-white metal. Its melting point is 937.4° Celsius, its boiling point is 2,830° Celsius, and its specific gravity is 5.32.
Description, Distribution, and Forms
Germanium forms a diamond-like tetrahedral crystal lattice similar to that of silicon. On the Mohs hardness scale, its hardness is six (diamond is ten). Germanium exhibits valences of +2 and +4. The +2 state is both easily reduced to the element and also oxidized to +4 germanium. Finely divided germanium ignites in chlorine gas to form germanium tetrachloride, and germanium forms a tetrahydride with hydrogen, which is a gas under ordinary conditions.
At low temperatures, pure germanium is almost an insulator because its four valence electrons are localized in the bonds between neighboring atoms. At room temperature, sufficient electrons enter higher-energy levels, become mobile, and conduct a weak current. The conductivity of germanium can be improved by the addition (doping) of 1 part per million of a Group V element, such as arsenic, because it has one more electron than germanium, or by the addition of a Group III element, such as indium, which has one less valence electron than germanium.
History
Germanium was discovered in 1886 by the German chemist Clemens Winkler and was named in honor of Germany. Ultrapure germanium is an intrinsic semiconductor, which accounts for its major use in solid-state electronics. Furthermore, it can be produced in near-crystalline perfection more easily than any other semiconductor. Thus the electronic properties of germanium have been widely studied. The earliest research on semiconductors was done with germanium, and William Shockley used it to make the first transistor in 1948.
Obtaining Germanium
Germanium is recovered by treating enriched wastes and residues from zinc sulfide ores, pyrometallic ores, and coal with hydrochloric acid to form a volatile liquid which is extracted with carbon tetrachloride and purified by distillation. The resulting germanium tetrachloride is treated with demineralized water to precipitate germanium dioxide, which is then reduced to germanium with hydrogen. The highly pure element, which contains impurities less than 1 part per million, is obtained by zone refining, a selective fusion-recrystallization process that concentrates impurities which can be removed from the melt.
Uses of Germanium
The major use of germanium is in semiconductor devices, such as transistors, diodes, solar cells, and solar batteries. It is also used in infrared optical devices, such as lenses, prisms, and windows, and germanium dioxide is used to produce optical glasses of high refractive index. Magnesium germanate is used in phosphors, and an alloy of germanium and gold is used in dental materials.
Bibliography
U.S. Geological Survey.