Indium is a rare, soft, silvery-white metal with distinct properties that make it valuable in modern technologies. It has a low melting point and exhibits transparency in thin films when oxidized. These unique characteristics have led to its use across various industrial and scientific applications.
Electronics and Display Technology
A primary application of indium is in Indium Tin Oxide (ITO), a material combining electrical conductivity with optical transparency. This dual functionality makes ITO vital for modern display technologies.
ITO serves as a transparent conductive coating in liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs), controlling individual pixels for image formation. In touchscreens for smartphones, tablets, and larger interactive displays, a thin layer of ITO senses electrical changes from touch, enabling responsive user interaction.
Beyond displays, indium is used in solar cells. ITO acts as a transparent electrode in various solar cell types, including thin-film and tandem cells, allowing sunlight to reach active layers and collect electricity. Indium is also a component in copper indium gallium selenide (CIGS) solar cells, a thin-film technology known for strong light absorption. In light-emitting diodes (LEDs), indium is found in compounds like Gallium Indium Nitride (GaInN), used in blue and white LEDs.
Specialized Alloys and Soldering
Indium’s ability to form low-melting point alloys is used in diverse engineering applications. These alloys can melt at relatively low temperatures, some as low as 46°C. This characteristic makes them suitable for specialized solders in electronics, protecting heat-sensitive components during assembly.
Indium-based solders offer improved resistance to thermal cycling, maintain ductility at cryogenic temperatures, and reduce the dissolution of precious metals like gold. The metal’s softness and malleability allow it to conform to irregular surfaces, beneficial in metallurgical processes and for bonding to non-metallic materials. These low-melting alloys are also found in safety devices like thermal fuses and fire detection systems, where their predictable melting behavior triggers safety mechanisms.
Other Industrial and Scientific Uses
Indium’s versatility extends to other specialized industrial and scientific applications. In the nuclear industry, indium is a component in control rods for nuclear reactors, often alloyed with silver and cadmium. These rods absorb neutrons to regulate fission, allowing precise control of power output and rapid shutdown.
In medical diagnostics, the radioisotope Indium-111 (In-111) is used in imaging. Indium-111 chloride labels white blood cells, which accumulate at infection or inflammation sites. This allows medical professionals to pinpoint these areas using SPECT scans, aiding in evaluating conditions like occult infections.
Indium is also used as a soft, deformable gasket material for ultra-high vacuum seals. Its malleability and low vapor pressure create tight, hermetic seals between materials like metals, glass, and ceramics, maintaining vacuum integrity in scientific instruments and aerospace components. Indium is also used in advanced battery technologies. Its use in lithium battery anodes enables faster charging and improves battery longevity by facilitating uniform lithium ion distribution. Indium can also serve as a protective coating on aircraft engine bearings, enhancing corrosion resistance and lubrication.