Applications of Indium

Metallic indium possesses excellent properties including good ductility, strong malleability, low melting point, high boiling point, low electrical resistance, and corrosion resistance. It also offers favorable optical permeability and electrical conductivity. These characteristics make indium widely used in aerospace, radio and electronics industries, medical devices, defense, high-tech sectors, and energy applications. The production of ITO (Indium Tin Oxide) targets — used in manufacturing liquid crystal displays and flat panel screens — represents the primary consumption area for indium ingots, accounting for 70% of global indium consumption. The electronics and semiconductor sector follows at 12%, solder and alloy applications at 12%, and research applications at 6%.

ITO Targets

Due to indium’s favorable optical permeability and electrical conductivity, the glassy composite of high-purity indium oxide and tin oxide (ITO) is used in the plasma television and LCD screen industry to create transparent conductive electrodes. It is also employed as sensitive elements in certain gas measurement devices. Globally, 70% of indium consumption is dedicated to ITO target production.

Electronics, Semiconductors, and Radio Applications

Indium exhibits high boiling point, low electrical resistance, and corrosion resistance, making it widely applicable in the electronics, semiconductor, and radio industries. A significant portion of metallic indium is used in the production of semiconductor materials. In the radio and electronics industry, indium is utilized to manufacture specialized contact devices, produced by mixing and pressing indium and silver oxides.

Indium in Solders and Alloys

When small amounts of indium are added to many alloys, it can enhance their strength, improve ductility, increase wear resistance, and boost corrosion resistance. This has earned indium the reputation of being the “vitamin of alloys,” with some referring to this phenomenon as the “remarkable indium effect.”

Indium alloys are used in solar cell production. Copper-Indium-Gallium-Selenide (CIGS) thin-film solar cells offer advantages such as low production costs, minimal environmental impact, no performance degradation, and good low-light performance. Their photoelectric conversion efficiency ranks highest among various thin-film solar cells, approaching that of crystalline silicon cells, while costs are approximately one-third of crystalline silicon cells. This has led to international recognition as a “very promising new-generation thin-film solar cell.” Additionally, these cells feature a soft, uniform black appearance, making them ideal for applications with high aesthetic requirements, such as glass curtain walls on large buildings, with significant market potential in modern high-rise architecture.

Due to its excellent ductility (malleability), low vapor pressure, and ability to adhere to various materials, indium is widely used as gaskets or lining materials in high-altitude instruments and aerospace equipment. Indium foil is commonly used as a contact material for ultrasonic linear transducers.

In the atomic energy industry, indium is used to manufacture neutron indicators. Many indium alloys are employed in producing control rods for nuclear reactors. Indium is also an excellent material for manufacturing neutron detectors, comparable to gallium metal.

The initial industrial application of metallic indium was in manufacturing industrial bearings, a use that continues to this day. Bearings with an indium-plated surface have service lives up to five times longer than those with conventional coatings. Indium-gallium alloys serve as lubricants for sliding components and are also used in electric vacuum instruments.

Indium readily forms strong coatings on metal surfaces and offers excellent corrosion resistance, particularly against alkaline solutions. Indium coatings not only exhibit bright colors but are also easy to polish. Beyond pure indium coatings, indium-zinc alloys are also used as coatings. Indium plating is also applied in decorative finishing. Mirrors, reflectors, and other reflective surfaces coated with indium demonstrate significantly enhanced reflective properties and resistance to seawater corrosion, making such coatings common on marine vessel reflectors. Additionally, bronze wire mesh plated with indium can be used to remove mercury vapor from vacuum instruments.

Due to its low melting point, indium can produce various fusible alloys. Indium-containing alloys with melting points ranging from 47°C to 122°C are commonly used to manufacture various fuses, circuit breakers, temperature controllers, and signaling devices.

Many indium-based fusible alloys are used as solders. Even pure metallic indium can easily wet and adhere strongly to the surfaces of glass, quartz, and mica. Indium enables robust welding of components made from piezoelectric materials. In manufacturing multilayer integrated circuits, selecting solder materials containing indium is a critical step.

A promising emerging application area for indium is in dentistry. Alloys used for dentures are primarily composed of gold, silver, and palladium, with 0.5% to 10% indium added. The addition of small amounts of indium to dental restoration materials significantly enhances their corrosion resistance and hardness while preventing tarnishing.

Overview of Indium Product Applications

Certain indium compounds — including oxides, sulfides, and phosphates — are used in manufacturing yellow and orange-yellow glass, as well as specialty optical glasses. Indium borate glasses containing bismuth or cadmium can absorb moderate-intensity X-rays and neutrons with energies higher than thermal neutrons.

Indium halides, such as indium iodide, are commonly used as additives in metal halide lamps to enhance lighting output and improve spectral quality.

**Indium Ingot**: Trapezoidal in shape, with a smooth, white surface and metallic luster. Primarily used in manufacturing various alloys, specialty solders, coatings, electronic components, and for producing high-purity indium.

**Indium(III) Oxide**: Pale yellow in color. Used in fluorescent screens, glass, ceramics, and chemical reagents.

**Indium(III) Hydroxide**: Used in batteries, glass, ceramics, and chemical reagents.

High-Purity Trimethylindium: White crystalline solid. Primarily used as a precursor in GAEHI (organometallic chemical vapor deposition) processes for epitaxially growing indium-containing compounds and semiconductor optoelectronic functional materials.

High-Purity **Indium(III) Chloride**: Colorless or white powder. Mainly used in manufacturing phosphors, III-V compound semiconductors, low-pressure sodium lamps, mercury-free anodes for manganese dry batteries, corrosion-inhibiting additives for zinc, and ITO transparent conductive films.

Indium serves as a dopant element in germanium transistors, with the largest quantity used in the production of PNP germanium transistors.

The consumption of indium in new applications grows at an annual rate of 10%–20%.

Due to its relatively soft nature, indium is also used in certain metal-filling applications for sealing gaps, such as vacuum gap filler materials at elevated temperatures.