Indium

Few people outside the world of chemistry know about the element indium; yet it is found playing a very important role in several commonly used products.

Indium is a soft, silver-white post-transitional metal, meaning its melting point of 156.6 degrees Celsius and boiling point of 2072 degrees Celsius are both lower than those of transitional metals. Due to this distance between melting and boiling points with indium, the element has an extraordinary large working liquid range.

Indium is also part of the alloy, galinstan, which is a non-toxic liquid at room temperature. This alloy is a combination gallium, indium and tin. 

There are several uses for indium that take advantage of its soft, malleable and ductile properties. The element is so soft (Mohs hardness 1.2) that it leaves a mark when drawn across a piece of paper, and can be cut into with a knife at room temperature. Due to its softness, it can be manipulated and easily drawn out into wire. One of the most common uses of indium wire is in high vacuum seals. As a wire, indium is also used as a thermal conductor in cryogenics and other ultra-high vacuums.

Indium’s low melting point lends it to being alloyed easily in solders. Another popular use for indium is in its foil form. Thin indium foil can be used as a conductive coating that is heated to fit between a heat-transfer surface of a microprocessor and heat sink.

Indium is also used in soldering, in order to provide a stress-free bond between a ceramic sputter target and a target holder. This bond is also electrical and thermal conducting. 

Indium is used for medical purposes as it emits a small amount of gamma radiation, which enables it to be used as a tracer throughout the body.

Although indium does not react with water, it can still be oxidized by other, stronger oxidizing agents like halogens, producing the indium(III) compounds like indium(III) oxide.

One of the most common uses for indium that appear in several commercial products is in the semiconductors and thin films used in the making of liquid crystal displays (LCDs).