German chemists Ferdinand Reich and Hieronymous Theodor Richter discovered indium in 1863. A brilliant indigo blue line in the sample's spectrum revealed the existence of indium. The element was named after the colour.
Indium is a very soft, silvery white metal with a brilliant lustre. The pure metal gives a high-pitched ‘scream’ when bent. China produces the majority of the world's supply of indium. There are no primary deposits of indium; it is all recovered from mining and processing of copper, zinc and tin ores.
Applications of Indium:
- Electronics: Currently, indium's primary application is in transparent electrodes made from indium tin oxide for liquid crystal displays. Indium compounds, such as indium antimonide, indium phosphide and indium nitride are used in semiconducting light-emitting diodes (LEDs) and Laser Diodes (LDs). It is used to dope germanium to make transistors and also to make other electrical components such as rectifiers, thermistors and photoconductors.
- Energy: Indium oxide and indium tin oxide are used as a transparent conductive coating applied to glass substrates in the making of electroluminescent panels. ITO is also used as a light filter in low pressure sodium vapor lamps. A rapidly growing use of indium is in the synthesis of the semiconductor copper indium gallium selenide, applied in the manufacture of thin film solar cells. Indium's high neutron capture cross section for thermal neutrons makes it suitable for use in control rods for nuclear reactors.
- Materials and Science: Indium is used for making particularly low melting temperature alloys. It is included as a component in some lead-free solders and in some dental amalgams. Plated onto metals or evaporated onto glass, indium form mirrors which are of as good quality as those made with silver but have a higher corrosion resistance. Very small amounts of indium are used in sacrificial, aluminum alloy anodes in salt water applications to prevent passivation of the aluminium.
- Other: Indium is used to provide a hard coating on bearings of high-speed motors and aircraft engines and facilitates an even distribution of lubricating oil on the bearing surface.