Indium
Indium is one of the rarest earth elements on planet Earth. It was discovered in 1863 by German chemist Ferdinand Reich and Theodor Richter. Indium is classified as a post-transition metal as it has properties of both a metal and a non-metal. It was named after the indigo blue line found in its spectrum. This element belongs to group 13 of the periodic table and has physical properties similar to those of gallium and thallium.
Indium is soft, malleable and can easily be cut with a knife. It is silvery-white in colour and has a face-centered cubic crystal structure. This element has an atomic number of 49, a relative atomic mass of 114.82, and atomic radius of 156 pm. Indium has a high thermal and electrical conductivity and can be thermally and electrically operated with relative ease.
Indium is found in small quantities in the Earth’s crust in association with zinc ore. It is most commonly mined from zinc smelting operations and can also be obtained as a by-product of lead, copper and tin processing. Other sources include cosmic dust, comet ices and meteorites. Indium is also produced synthetically, most often through the electrolysis of indium(III) chloride.
The most important uses of indium are as an alloying agent to improve the strength and ductility of copper and tin metals. It is also used to make soldering, bonding and brazing alloys, and as an additive in low-temperature solders. These solders are used in the manufacture of electronics, such as transistors and their components, computer chips and vacuum tube elements.
Indium is also used in some fluorescent lamps, in special high- temperature and high-vacuum valves, and in low-melting bearing alloys. Indium-tin oxide is a common transparent conductive material and is used in some touch screens and flat-panel displays. Indium alloys are used in aircraft and spacecraft, as well as in medical prosthetics, such as hip and knee replacements.
Because of its rarity and cost, indium is usually recovered and recycled rather than being discarded. One of the main methods for recovering indium is by-product recovery from ores, specifically zinc ores. Other methods include recovering and recycling indium from alloys and scrap, as well as landfill mining.
Indium is a vital, yet limited, resource that is becoming increasingly popular due to its uses in the electronic and medical industries. As the demand increases, it is becoming increasingly important to ensure that this valuable resource is sustainably harvested and recycled in a responsible and efficient manner.
