In - Indium

Properties

Indium is a soft, silvery metal that is a member of Group 13 of the Periodic Table. It is the 69th most abundant element within the Earth’s crust. It is stable in air and water, but dissolves in acids. Indium is very characteristic as being extremely ductile in its metal form, which is unusual for most metals. This is due to it having one of the longest liquid range of all the elements.

History

Indium was discovered in 1863 by Ferdinand Reich and Hieronymous Richter at the Frieberg School of Mines in Germany. Reich was Professor of Physics and was investigating a sample of the mineral zinc blende (now known as sphalerite, ZnS), which he believed might contain the recently discovered thallium. He produced a yellow precipitate which he thought was thallium sulfide, but his atomic spectroscope showed lines that were not those of thallium. Because he was colour blind, he referred to his colleague, Richter, to look at the spectrum, and what he saw was a brilliant violet line, giving rise to the name ‘indium’ for the new element. They realised that a significant amount of indium must be present in the zinc blende, and were able to isolate a small sample of the new element. Together they published a paper announcing the discovery but later fell out when Richter exhibited samples of the new metal at the Academie des Sciences, Paris, in April 1867, and attempted to claim the discovery for himself alone.

Sources

Although an indium mineral, ‘indite’, has been discovered in Siberia, it is too rare to extract.  Indium is instead recovered as a by-product of lead and zinc smelting, and occurs in lead and zinc sulphide ores at a frequency of 1%.  The world production of indium is approximately 75mts per year with over 1,500mts in reserves, and in 2009 the world total was about 600mts (including that which is recycled).  The main producing nations are naturally those involved in lead and zinc production.  These are: the US, Belgium, Brazil, Canada, China, Japan, South Korea, Peru, Russia and others.  A great deal of indium is recycled, mainly from processes such as ITO (Indium Tin Oxide) sputtering, (an inefficient process wasting approximately 70% of the indium used). This 70% is recovered mainly in China, Japan and South Korea, where the production and sputtering of ITO takes place.  At times, when indium prices are high, indium is recovered from scrap LCD (Liquid Crystal Display) panels themselves, however this is otherwise not economically viable.

Uses

Today indium is mainly consumed in the form of ITO, and this is the application with the biggest global consumption.  ITO is such a popular use for indium, as it sticks to glass and when evaporated and allowed to deposit onto a substrate such as glass, it creates a mirror effect more reflective and corrosion resistant than silver.  ITO applications revolve around its electric conductivity, and are thus used in LCDs for flat panel devices (such as mobile phone, computer and TV screens), as a solder, alloys, electrical components and semiconductors.  The semiconductors or transistors are made of low-melting alloys: indium arsenide (InAs) and indium antimonide (InSb).  The isotope indium 115 is used in a more obscure application, as a way of assessing the inner workings of nuclear reactors, due to its high-neutron capturing abilities.  A relatively new application of indium is as a semiconductor in the compound copper-indium-gallium-diselenide (CIGS) used in solar panels.