indium

Indium is a chemical element with the symbol In and atomic number 49. It is a soft, ductile post-transition metal in group 13. In its pure form, it appears as a silvery-blue metal and has a relatively low melting point of 156.6°C. It forms a protective oxide layer, In2O3, on its surface, which gives it good corrosion resistance.

Indium occurs only at trace levels in the Earth's crust and is chiefly found in zinc ores as a byproduct of zinc refining. It is rarely found as a native metal. Because it is primarily recovered from zinc production, indium supply is closely tied to zinc market conditions.

Indium was discovered in 1863 by Ferdinand Reich and Hieronymus Theodor Richter through spectroscopic analysis of zinc ore. The name is derived from the indigo spectral line observed in the ore.

Indium has widespread use in electronics and optoelectronics. The most important indium compound is indium oxide (In2O3), which, when doped with tin to form indium tin oxide (ITO), serves as a transparent conductor for touch screens, liquid-crystal displays, and solar cells. Other important compounds include indium phosphide (InP), indium gallium arsenide (InGaAs), and indium antimonide (InSb), which are used in high-speed electronics, LEDs, and infrared detectors. In metal form, indium is used as a coating for bearings, in low-melting-point solders and thermal interface materials, and in cryogenic seals due to its malleability.