Indium (In)
Indium (In) is a relatively rare element found in the Earth's crust, closely resembling aluminum in its properties. With an atomic number of 49, it has two naturally occurring isotopes and is primarily extracted as a by-product of zinc production. Indium is not found in its free metallic form; instead, it occurs in various minerals, especially in ores rich in zinc, copper, lead, and tin. Key locations for indium extraction include Colorado, Argentina, the United Kingdom, and Canada.
Indium plays a crucial role in the electronics industry, being utilized in applications such as liquid-crystal displays, transistors, and solar cells. It is also important in the production of alloys, solders, and coatings, thanks to its unique properties, like its ability to adhere to glass. Historically discovered in 1863, indium was first industrially applied in automotive and aircraft engine bearings before expanding into its current widespread uses. With its versatility and significant industrial applications, indium continues to be an essential material in modern technology.
Indium (In)
Where Found
Indium is widely distributed in the Earth’s crust in small amounts. It is fairly rare and is about as common as silver. Indium is never found as a free metal but only in combination with other elements. It is found as a trace component in many minerals, particularly in ores of zinc, copper, lead, and tin. The richest concentrations of indium are found in Colorado, Argentina, the United Kingdom, and Canada.
Primary Uses
Indium is used for a variety of purposes in the electronics industry, including liquid-crystal displays and transistors. It is also used in batteries, solders, coatings for glass, sealants, and alloys that melt at low temperatures.
Technical Definition
Indium (abbreviated In), atomic number 49, belongs to Group IIIA of the periodic table of the elements and resembles aluminum in its chemical and physical properties. It has two naturally occurring isotopes and an average atomic weight of 114.82. Pure indium is a soft, white metal. Its density is 7.31 grams per cubic centimeter; it has a melting point of 156.61° Celsius and a boiling point of 2,080° Celsius.
Description, Distribution, and Forms
Indium, a fairly uncommon element, occurs in the Earth’s crust with an average concentration of about one part in ten million. It is most commonly found in ores that are rich in zinc, particularly those which contain sphalerite (zinc sulfide). It is also found in ores of copper, lead, and tin.
History
Indium was discovered in 1863 by Ferdinand Reich and Hieronymous Theodor Richter. It was not produced in large amounts until 1940. Its first major industrial use was in the production of automobile and aircraft engine bearings, where it added strength, hardness, resistance to corrosion, and ability to retain a coating of oil. In the 1960’s, it was first used in transistors.
Obtaining Indium
Indium is usually obtained as a by-product of zinc production. A variety of methods exist for obtaining indium from the residue left over after most of the zinc is removed from the ore. One method involves treating the residue with dilute sulfuric acid to dissolve the remaining zinc. The undissolved material left behind is then treated with stronger acid to dissolve the indium. The indium is treated with zinc oxide to obtain indium hydroxide or with sodium sulfite or sodium bisulfite to obtain indium sulfite. Pure indium metal is then obtained by subjecting these compounds to electrolysis.
Uses of Indium
Indium is often combined with other metals such as bismuth, cadmium, lead, and tin to form alloys with a low melting point; production of indium tin oxide was the most common end use worldwide as of 2008. These alloys are used in fuses and heat-detecting sprinkler systems. It has also been mixed with lead to form solders that remain flexible over a wide range of temperatures. Molten indium has the unusual property of clinging to glass and other smooth surfaces and is often used to form seals and coatings. High-purity indium is used in combination with germanium to form transistors. The electronics industry also uses indium in liquid-crystal displays, infrared detectors, and solar cells.
Bibliography
Natural Resources Canada.
U.S. Geological Survey.