Tantalum (Ta) is an essential element for various sectors in the modern electronics market. One of the rarest elements on earth, tantalum is used in enormous quantities in both pure and alloy forms. Alloys, such as tantalum-3wt%tungsten (Ta3W), are important due to their higher strength and superior corrosion resistance compared to pure tantalum. Tantalum subsequently offers limitless material potential and tangible results in challenging markets.
Tantalum is a rare element that is highly prized for its applications in industry and emerging technologies. As a refractory metal, tantalum has a very high density (16.7 g/cm3 at room temperature), a very high melting point (3017 C), and good mechanical strength at high temperatures.
Tantalum stands out from other refractory metals due to its extreme chemical inertness and electrical properties, which make it suitable for a range of unique applications. Tantalum also exhibits compatibility with silicon and silicon dioxide, making it a highly valuable material for semiconductor processing.
Properties of Tantalum
Tantalum is an extremely rare transition metal that has a lustrous grey finish, similar in tone to platinum. Its discovery in 1802 was challenged by contemporary chemists who claimed it was not a new element but was an allotrope of niobium. The two are almost chemically-identical and are still difficult to distinguish from one another today. In a wide range of industrial acids and liquids, tantalum is the most corrosion resistant metal available with corrosion resistance comparable to glass in many acids.
With a density of 16.6 g/cm3, tantalum is twice as dense as steel with a Mohs hardness of approximately 6. This is despite high ductility at room and elevated temperatures and an exceedingly high melting point of 2996°C (5425°F) – the fourth highest of all known metals.
Semiconductor materials, such as silicon, have enabled drastic size reductions (and corresponding performance improvements) in electronics. Today, semiconductor technologies are the building blocks of virtually all electronic devices, and the basis of a trillion-dollar industry.
As the critical dimensions of semiconductor devices continue to decrease, semiconductor manufacturers rely increasingly on materials science to solve problems that arise in nanoscale features. Tantalum plays a crucial role in many semiconductor devices by facilitating the use of copper interconnects in devices such as logic chips and DRAMS. Unlike copper (and other comparable metals), tantalum atoms do not diffuse into silicon at chip operating temperatures. High-purity tantalum nitrides can be grown on top of copper chips to stop electromigration of copper atoms. This ensures that the semiconductor devices remain reliable for longer.
Tantalum exhibits extreme chemical inertness, resisting corrosion from a wide range of acids and other corrosive chemicals. Tantalum alloys, such as ULTRA 76+ which exhibit significantly improved corrosion resistance compared to the more traditional Ta-2.5W alloy, are invaluable for producing chemical processing equipment exposed to high temperature chemical attack. Tantalum alloys are used to produce equipment such as heat exchangers, piping, tank cladding, valve liners, feed lances, and rupture disks; ensuring reliable and long-life service under extreme process conditions.
While tantalum is conductive, tantalum oxide (Ta2O5) has a very high electromagnetic permittivity ( ). This means that tantalum can be used to create small capacitors with very high capacitance.
Tantalum capacitors are typically manufactured by pressing and sintering pure tantalum into a porous pellet with a large effective surface area – a very small tantalum capacitor typically has a capacitance equal to that of a much larger conventional capacitor plate.2 Formation of a thin oxide surface layer via anodization contributes to the high capacitance of the pellet. The capacitance of a tantalum capacitor can be much higher than that of equivalently sized ceramic or aluminum capacitors, a fact which earns tantalum capacitors widespread use in compact electronic devices such as cellphones and computers.
Tantalum oxide, which naturally forms on the surface of pure tantalum when exposed to air, is completely inert to bodily fluids and, as a result, highly biocompatible. Tantalum is therefore a highly desirable material for the construction of strong and durable surgical implants. Surgical applications of tantalum include hip and knee replacement fixtures, monofilament and braided suture wires for skin closure (as well as tendon and nerve repair), clips for blood vessel ligation, staples for abdominal surgery, and plates for reconstructive surgeries.
As tantalum capacitors are highly durable and can be made very small, they are commonly used in implantable medical devices, particularly implantable cardioverter defibrillators (ICDs).
Military and Aerospace
Tantalum additions to nickel-based superalloys can yield materials capable of withstanding extremely high temperatures and mechanical stress. Such superalloys are used extensively in the production of gas turbine engines for military and commercial aircraft as well as land-based power generation. High temperature strength and good dimensional stability are both essential qualities for such applications. Components made from alloys containing tantalum can handle higher internal combustion temperatures, which results in enhanced thrust efficiencies and lower fuel consumption.
Furnace boats and trays are used to hold finished or semi-finished products during high-temperature furnace processes such as annealing and sintering. Such containers must be able to withstand rapid and repeated temperature cycling to extremely high temperatures. Tantalum excels in such applications, offering strength and dimensional stability at high process temperatures and exhibiting excellent resistance to creep deformation.
Tantalum and Tantalum Alloys from H.C. Starck Solutions
H.C. Starck Solutions is one of the world’s largest suppliers of pure tantalum and tantalum alloys for engineering applications. Manufactured via a combination of thermo-mechanical processes refined over decades, our signature NRC®76 (Ta2.5%W) welded tubing offers a defect-free product with a tightly controlled composition and uniform wall thickness which is paramount in engineering calculations to secure safety for many years in operation.
Our ongoing research into tantalum alloys resulted in the development of ULTRA76+, a modified Ta2.5%W alloy with superlative mechanical and anti-corrosion properties and a reduced cost when compared with the previous generation ULTRA76 alloy.
For semiconductor and electronics applications, tantalum is often sputtered to produce thin tantalum layers. H.C. Starck is a major producer of high-purity tantalum sputtering target blanks, exhibiting highly controlled grain size with low defect rates.
To find out more about our comprehensive range of tantalum materials and solutions, get in touch with a member of the H.C. Starck team today.