Indium has a unique and even romantic sounding name. The name results from the line in its spectrum – an intense indigo. Although the process of indium bonding is currently at the fore of many experimental processes, the metal, itself, deserves attention for its discovery and rarity. It is truly a unique metal – if only for its color and “scream.”
A Brief History of Indium
Indium is a soft, silvery-white metal that has laid quietly inside the earth’s crust for thousands of years. However, no one had heard of it until 1863. In that year, two German chemists, Ferdinand Reich (1799–1882) and Hieronymous Theodor Richter (1824–1898) discovered it while they were both at the Freiberg University of Mining and Technology. They were examining zinc ore at the time with a spectrograph. They were searching for thallium. Instead, Richter was surprised to see a bright blue and very distinct stripe that was not cesium.
The two gave this new metal the name indium – after the distinctive colored stripe. However, the ability to extract and use it was not part of their mandate. In fact, this did not occur until the early 20th century. From the years 1924 to 1933, Daniel Gray, a James Milliken University graduate, working with Dr. William S. Murray, the founder of Indium Corporation, came up with the means to accomplish this. Indium was now about to become a commercial product.
Sourcing Indium
Arizona yielded the first commercial amounts of indium in 1926. However, the full potential for the metal was slow developing because of its rarity. The main source of indium is zinc ores although it can be found in some copper, iron and lead ores. The main producers of the product for use in indium bonding and other applications are Canada, China and Russia.
Qualities and Applications
Indium is a post-transition metal indicating its poor conductivity and softness when compared with other metals. Indeed, indium is classified as one of the softest known metals. Its properties include both a low boiling and melting point making it ideal for soldering. However, fabricators also remark on the metal for its ability to “scream” when they bend it.
Screaming aside, the qualities make indium ideal for producing both bearing and low melting alloys. It is use in:
* Germanium transistors
* Liquid crystal displays
* Photocells
* Photoconductors
* Rectifiers
* Thermistors
* Transparent conductors
Perhaps the most mystical property of all is not the screaming but the uniqueness of this metal. It allows fabricators to evaporate it onto glass where it then forms a mirror. Alternatively, they can plate it onto metal.
Indium Bonding
Indium serves a variety of purposes because of its thermal and electrical properties. When combined with its low melting point, indium is extremely useful in bonding. As such, indium has proven useful in the past, and will continue in the future, to meet specific needs. It is becoming indispensable for the production of not only thermistors and photoconductors, but also the creation of alloys. In fact, the demand for indium bonding has resulted in an almost tenfold increase in the price of the substance since 2002.
