Indium

Background

Indium was discovered by Reich and Richter in 1863 and was named after the brilliant indigo line which it displays in its atomic spectrum.

Occurrence

Indium is most often found with zinc minerals and is never found as a free element. Commercially it is found as a by-product of zinc, lead iron and copper ores. It is isolated by the electrolysis of indium slats in water.

Key Properties

Indium is:

· Very soft

· Silvery white in appearance

· Has a brilliant lustre

· Emits a high pitched cry similar to gallium when bent

· It is wetting towards glass

· It is stable in air and water but dissolves in acids

Applications

Applications for indium include:

· Low melting point alloys (e.g. 24% indium, 76% gallium is liquid at room temperature)

· Solders

· Bearing alloys

· Germanium transistors

· Rectifiers

· Thermistors

· Photoconductors

· Mirrors, where it can be plated onto metals or evaporated onto glass

Indium compounds are used in:

· Semiconductors – Indium phosphide

· Liquid crystal displays (LCD) – Indium tin oxide