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Tantalum: Properties, Processing, and Applications

In spite of being a relatively rare metal (0.8 mg/kg of the Earth’s crust, on average), tantalum plays a vital role in modern electronics technology and also has applications in biomedical devices, corrosion-resistant coatings, and aerospace applications. Because tantalum is both scarce while offering desirable chemical properties, it is often used in forms that save materials, such as coatings, wires, and powders. Matmatch offers tantalum in a variety of forms to suit different applications and processing requirements.

In this article, we will discuss:

  • The material properties of tantalum that make it a vital part of modern technology
  • How tantalum is processed from raw ore into a useable form
  • How tantalum is used in electronics, biomedical devices, and other applications

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Properties of Tantalum

Tantalum is both useful for storing electricity and resisting hostile environments. This table summarizes key material properties of tantalum as well as the applications that take advantage of a particular property.

Material Property

Value

Relevant Application

Electrical conductivity (metal)

8x106 S.m–1

Conductive layers in capacitor

Dielectric constant of oxide

25

Dielectric (insulating) layer in capacitor

Corrosion and chemical resistance

Excellent

Corrosion-resistance coatings

Biocompatibility

Excellent

Coatings on implant surfaces

Thermal conductivity

54.4 Wm–1K–1

Heat transfer in aerospace engines

Melting point

2996°C

Heat-resistant superalloys

Density

16.6 g/cm3

Radiation-resistant electronics for outer space

How is tantalum processed?

Tantalum is manufactured and purified using a multi-step chemical process.

  1. Ore extraction (tantalite, microlite, wodginite) or recycling
  2. Digestion with sulfuric acid at high temperature
  3. Solvent extraction of tantalum-containing species
  4. Conversion to tantalum fluoride or tantalum oxide
  5. Reduction to tantalum powder
  6. Processing into bar, plate, sheet, rod, tube, and wire forms

 

Tantalum is often produced alongside niobium, which has very similar chemical properties and tends to appear in the same regional mineral deposits as tantalum. When they were discovered, tantalum and niobium were so similar that at first they were thought to be the same element. Niobium is a fascinating material in its own right. Though it is mostly used as an additive to improve the mechanical properties of low-alloy steels, niobium is also an important ingredient in superconducting magnets and catalysts for manufacturing biofuels. 

Applications of tantalum

About half of the tantalum produced globally is used in electronic devices, particularly in electrolytic capacitors. Tantalum can be made to grow a very thin continuous oxide layer. The underlying tantalum metal can then be used as a charge-storing electrode in the capacitor while the oxide acts as the dielectric material, thus creating both the insulating and conducting components of the capacitor simply by growing an oxide layer. The tantalum oxide layer itself is an excellent insulator and can be made extremely thin, which improves the capacitance while keeping the device small. Because tantalum-based capacitors offer high capacitances in a small and lightweight package, they have become a vital component of modern portable electronics devices, and most tantalum produced annually is used by the electronics industry. In order to save tantalum, the capacitors use very thin foils of tantalum and any excess material is often recycled. This chart summarizes the most common forms of tantalum, many of which are available through Matmatch.

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Source for plot data: https://www.bgs.ac.uk/downloads/start.cfm?id=2033

 

Tantalum is also highly resistant to corrosion and does not cause irritation when in contact with human tissues, which makes it very useful in biomedical devices, surgical tools, and implants. For example, tantalum can be coated onto carbon foams using chemical vapor deposition (CVD) processes, resulting in a highly porous “scaffold” that can be used on the surface of joint replacement implants. The porous scaffold closely matches the mechanical properties of bone, and because of tantalum’s excellent biocompatibility, bone can grow into the scaffold and create a strong bond between the patient’s bone and the implant. By using tantalum as a coating, the implant gains all the benefits of tantalum’s biocompatibility while using as little tantalum as possible.

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Tantalum is highly resistant to chemical attack and corrosion in hostile environments outside the human body as well. Only a thin coating of tantalum is required to grant protection against caustic chemicals. Such coatings can be applied by electrodeposition, sputtering, or chemical vapor deposition. Even coatings a few microns thick can shield a part while requiring a relatively small amount of tantalum. Tantalum also helps stabilize the grain boundaries of other metals, which makes it helpful in preserving the microstructures of alloys that are used in high-temperature applications.

Because of its high melting temperature, tantalum is an important ingredient in superalloys - high-performance metal mixtures designed to withstand the extreme temperatures inside of jet engines. Superalloys are critical to modern aircraft engines since they allow the engines to operate at higher temperatures with improved fuel efficiency. Tantalum has also been used in alloys and carbides in space vehicles, particularly in parts like rocket nozzles which must maintain their structural strength even at high temperatures. Unlike their uses in electronics, biomedicine, and corrosion-resistance coatings, aerospace applications of tantalum are so critical that saving material is much less of a consideration. Tantalum has also seen some more specialized applications, such as being part of the “radiation vault” and electronics used in the Juno space probe, where the high density of tantalum made it a good choice for defending against radiation in space.

Tantalum also appears in a variety of compounds that are used in a variety of industries. Tantalum carbide is a hard, strong substance usually used in cutting tools. Lithium tantalate is used to create surface acoustic wave (SAW) filters in various audio applications to improve the sound quality of speakers. Tantalum oxide has a high index of refraction, which makes it ideal for making thin, light lenses for cameras, phones, eyeglasses, etc. Tantalum oxide is also useful as a filter for X-ray and as a coating to grant wear-resistance to components of inkjet printers.

Conclusion

In spite of being a relatively scarce metal, tantalum is one of the most technologically important materials in the world due to the essential role it plays in electronics, biomedical devices, superalloys, and corrosion-resistant coatings. Tantalum often plays the role of protecting other metals, whether the tantalum is used in a thin coating to protect its substrate from chemical attack, or as an additive in superalloys to improve their high-temperature performance. Tantalum’s ability to grow a thin continuous oxide which is an excellent insulator makes it possible to create small, high-capacitance capacitors which are a critical component of modern electronics. Tantalum is a multi-purpose material that fills a huge variety of niches in technology. Matmatch offers tantalum in a variety of forms to suit a wide range of applications and processing requirements.

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