Indium

Indium is a chemical element in the periodic table that has the symbol In and atomic number 49. This rare, soft, malleable and easily fusible true metal, is chemically similar to aluminum or gallium but looks more like zinc (zinc ores are also the primary source of this metal). Its current primary application is to form thin-films for use as lubricated layers (during WWII it was widely used to coat bearings in high-performance aircraft).

Table of contents

1 Notable Characteristics
2 Applications
3 History
4 Occurrence
5 Precautions
6 External Links

Notable Characteristics

Indium is a very soft, silvery-white true metal that has a bright luster. As a pure metal indium emits a high-pitched "cry" when it is bent. Both gallium and indium are able to wet glass.

Applications

The first large-scale application for indium was as a coating for bearingss in high-performance aircraft engines during World War II. Afterwards, production gradually increased as new uses were found in fusible alloys, solders, and electronics. In the middle and late 1980s, the development of indium phosphide semiconductors and indium-tin-oxide thin films for liquid crystal displays (LCD) aroused much interest. By 1992, the thin-film application had become the largest end use. Other uses;

Used in the manufacture of low-melting alloys. An alloy consisting of 24% indium and 76% gallium is liquid at room temperature.
Used to make photoconductors, germanium transistors, rectifiers, and thermistors.
Can also be plated onto metals and evaporated onto glass which forms a mirror which is as good as those made with silver but has higher corrosion resistance.
Its oxide is used in the making of electroluminescent panels.

History

Indium (named after the indigo line in its atomic spectrum) was discovered by Ferdinand Reich and Theodore Richter in 1863 while they were testing zinc ores with a spectrograph in search of thallium. Richter went on to isolate the metal in 1867.

Occurrence

Indium is produced mainly from residues generated during zinc ore processing but is also found in iron, lead, and copper ores. The amount of indium consumed is largely a function of worldwide LCD production. Increased manufacturing efficiency and recycling (especially in Japan) maintain a balance between demand and supply. The average indium price for 2000 was US$188188 per kilogram.

Up until 1924, there was only about a gram of isolated indium on the planet. The Earth is estimated to contain abou 0.1 ppm of indium which means it is about as abundant as silver. Canada is a leading producer of indium, producing more than 1,000,000 troy ounces in 1997.

Precautions

There is some unconfirmed evidence that suggests that indium has a low level of toxicity. However in the welding and semiconductor industries, where indium exposure is relatively high, there have been no reports of any toxic side-effects.