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Tantalum. Image Credit: Shutterstock.com/RHJPhtotos

Tantalum: Definition, Characteristics, Properties, and Applications

Xomety X
By Team Xometry
October 13, 2023
 11 min read
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Tantalum is a transition metal element with the symbol Ta. It is a rare and dense metal known for its exceptional corrosion resistance and high melting point. It exists in the geology as a range of ores and is not present in the metallic state in nature. Tantalum is employed, either as a metal, in an alloy, or as one of its salts, in various industries and applications including: aerospace, electronics, military and defense, and jewelry. This article will discuss tantalum, its symbol, characteristics, properties, and applications.

What Is Tantalum?

Tantalum is a rare, hard, and very dense elemental metal with a lustrous, gray-blue silver appearance. It belongs to the transition metal group, situated in the same group as niobium, titanium, tungsten, and molybdenum. To learn more, see our guide on the Properties of Metalloids.

What Is the Symbol of Tantalum?

The periodic table representation of tantalum is Ta.

What Is the Atomic Number of Tantalum?

Tantalum has an atomic number of 73, and it is not radioactive. There are 60+ synthetic and projected isotopes and nuclear isomers of tantalum ranging from 155Ta to 190Ta, with metastable sub-variations of some isotopes listed as m1–m6. Nuclear isomers contain one or more neutrons in an excited energy state that is liable to decay, making them not necessarily differentiated isotopes but isomers. All these synthetic forms are radioactive, with half-lives varying between 1.82 years (179Ta) and 56.56 hours (177Ta).

What Is the Atomic Weight of Tantalum?

The only naturally occurring isotope of tantalum has an atomic mass of 180.95—with various isotopes diverging slightly from this value as the nucleus becomes altered under bombardment.

What Is the Other Term for Tantalum?

Tantalum has had a variety of other names historically applied to it, because of its close association with niobium ores (columbite, niobite-tantalite, columbate). However, such naming became unusual as the element was isolated, studied, and in time placed into the periodic table distinct from other metals. It is often present in broad-spectrum rare-earth oxide ores in which either or both niobium or tantalum are present (fergusonite).

What Is Tantalum Made Of?

Tantalum is an element. It is made of indivisible, atomic tantalum, which can be formed into a range of synthetic, radioactive isotopes that essentially remain tantalum. Where it is alloyed with other constituents such as tungsten and niobium, the resulting alloys inherit improved properties that make them considerably more ductile than the non-tantalum components. These materials can often be referred to as tantalum, despite their various constituents.

What Is the History of Tantalum?

Tantalum was first identified by Anders Gustaf Ekeberg in 1802. He initially named it "tantalum" after the Greek mythological character Tantalus, because it was tantalizingly difficult to oxidize. In the late 19th century, tantalum's high melting point and resistance to corrosion made it of interest to metallurgists. During World War II, tantalum was used in the production of electrical components, such as capacitors and rectifiers, for military equipment. Tantalum capacitors have become widely used in electronics due to their reliability and stability. The nuclear power sector also began to rely on the metal for its stability under radiation bombardment. The medical sector began employing it due to its biocompatibility, and chemical processing started to rely on it for reaction chambers that were stable under aggressive conditions. Now, tantalum holds an increasingly important position in many industrial sectors in which its benefits outweigh its very high costs.

What Are the Characteristics of Tantalum?

The metal in its pure form has a range of very useful properties, and as an alloying agent, it can carry many of these over into the resultant alloys. Some of tantalum’s characteristics are:

  1. Has very high corrosion resistance in aggressive environments, including acids and hot, concentrated alkalis. 
  2. Because of its unreactive nature, it is biocompatible and non-irritant in skin and implanted applications.
  3. It has moderate to high ductility, similar to steel. Alloys containing tantalum with elements such as tungsten benefit from this ductility.
  4. Is a strong conductor of electricity.
  5. Has a lustrous, gray-blue silver appearance.

What Is the Color of Tantalum?

Metallic tantalum is a lustrous, blue/gray silver color. Its ores, such as tantalite, are dark brown to black rocks.

What Does Tantalum Look Like?

Tantalum has the appearance of a bright metal. It retains its color as it suffers virtually no oxidation or other chemical reactions under normal environmental conditions.

What Is the Density of Tantalum?

Tantalum is a dense element, at 16.69 g/cm³—some 50% more than that of lead and more than twice the density of iron.

What Type of Metal Is Tantalum?

It is a transition metal, from the central portion of the table, clustered with niobium, molybdenum, and tungsten. It has a crystal structure that is BCC (body-centered cubic).

Is Tantalum Magnetic?

No, tantalum does not respond to magnetic fields.

Is Tantalum Lightweight?

No, tantalum is a very dense metal.

Is Tantalum Durable?

Yes, tantalum is resilient under extreme loads and abrasive action, even at highly elevated temperatures.

Is Tantalum Ductile?

Yes, tantalum is ductile, which is unusual for a metal with a BCC crystal structure. To learn more, see our guide on What is Ductility.

Is Tantalum Rust-Proof?

Yes, tantalum is extremely resistant to oxidation and shows almost no environmental response, even at high temperatures. The exception to this is its response to hydrofluoric acid and other fluoride-containing reactants.

Is Tantalum Weldable?

Yes, tantalum is weldable by resistance welding, gas tungsten arc welding, plasma welding, and electron-beam welding. It can also be successfully welded to other metals, except that some combinations result in brittle intermetallic phases at the joint.

What Are the Properties of Tantalum?

Tantalum has a wide range of attractive properties that recommend it across a spectrum of challenging and high-value applications, including: 

  1. High melting point at 3,017 °C.
  2. Very high corrosion resistance.
  3. Has moderate to high ductility.
  4. Strong conductor of electricity.

What Are the Physical Properties of Tantalum?

Table 1 below shows some physical properties of tantalum:

Table 1: Physical Properties of Tantalum
PropertyDefinitionUnitsImportance
Property
Color
Definition
Lustrous blue/gray
Units
-
Importance
-
Property
Density
Definition
Mass per unit volume
Units
16.69 g/cm³
Importance
Moderate
Property
Melting point
Definition
Liquefaction temperature
Units
2,996 to 3,017 °C
Importance
High
Property
Tensile strength
Definition
Loading at failure
Units
170–300 MPa
Importance
High
Property
Yield strength
Definition
Loading at 0.2% extension (typical)
Units
100–200 MPa
Importance
High
Property
Hardness
Definition
Resistance to the diamond indenter
Units
90–120 Vickers
Importance
-
Property
Ductility
Definition
Ability to undergo plastic deformation without fracture
Units
Moderate
Importance
High
Property
Resistivity
Definition
Resistance typical level
Units
1.3x10^-7 mΩ
Importance
Moderate
Property
Biocompatibility
Definition
Chemical and electrochemical effects on living tissues
Units
-
Importance
High

What Are the Chemical Properties of Tantalum?

Table 2 below shows some chemical properties of tantalum:

Table 2: Chemical Properties of Tantalum
PropertyDefinitionExampleUnitsImportance
Property
Reactivity
Definition
Response to acids, alkalis, and oxygen-rich environments
Example
Non-oxidizing in combustion environments
Units
-
Importance
High
Property
Superconductivity
Definition
Zero electrical resistance
Example
Scientific equipment
Units
-
Importance
Moderate
Property
Electronegativity
Definition
Readiness to react
Example
-
Units
1.5 Pauling
Importance
High

What Are the Applications of Tantalum?

Tantalum has been used in various applications as discussed below:

1. Electronics

Tantalum pentoxide (and other oxides) serve as highly stable and robust electrolyte coatings for the sintered tantalum anode in capacitors. The use of tantalum allows greater capacitance in smaller packages, offsetting the raw material’s high cost.

In semiconductors, metallic tantalum plays a critical role in that a layer of a few atoms is sputter-coated onto a silicon wafer to chemically isolate the copper conductors which would otherwise diffuse progressively into the wafer. Lithium tantalate crystals are used as surface acoustic wave filters in audio circuits, to improve signal quality by improving electronic signal wave damping and frequency control.

2. Applications Involving High Temperatures

Tantalum has a very high melting point, in excess of 3,000 °C. Tantalum and its alloys find application wherever a metal component suffers exposure to extreme temperatures and must maintain low reactivity, high strength, and dimensional stability. This can be in gas turbine and rocket combustion chambers, reaction vessels, nuclear reactor containment structures, and a wide range of scientific, metallurgical, and research applications.

3. Alloys

A range of alloys use tantalum as a component, benefiting from enhanced properties gained from the blend. For example, tantalum-tungsten alloys in varying component proportions possess high-temperature strength and improved ductility compared with pure tungsten. These alloys are often used in high-temperature applications such as jet engines and rocket nozzles. Tantalum-niobium alloys (or superalloys), on the other hand, are ideal for chemical processing equipment that comes into contact with highly corrosive environments/reactions. They are also used in the manufacture of sputtering targets for thin-film deposition in the semiconductor industry. Meanwhile, tantalum-hafnium alloys have exceptional high-temperature mechanical properties. They are suitable for applications in which highly loaded components experience periodic or long-term extreme temperatures, such as in the aerospace engine and nuclear sectors. Finally, tantalum-zirconium alloys are widely used because of their resistance to extremely acidic and alkaline environments in chemical processing equipment and similarly aggressive environments.

To learn more, see our guide on Alloy Metal.

4. Corrosive Chemical Handling

Tantalum and many of its alloys are ideally suited to operation in corrosive and elevated temperature/pressure environments as the range of reactive sensitivities is limited and alloys can be selected appropriately. The only vulnerability of tantalum is in fluoride-based reactive chemistries such as hydrofluoric acid.

5. Surgical Implants

The extremely low to zero reactivity of tantalum and many of its alloys makes them ideal for surgical implants, in which no sensitization and biocompatibility issues arise.

What Are the Benefits of Tantalum?

Overall, tantalum as an elemental material, an oxide or salt, and as an alloy component has a wide range of beneficial characteristics including:

  1. As an electrolyte, tantalum pentoxide and other oxides facilitate high capacitance per unit mass of capacitor. This allows very small format components to deliver a high value of capacitance.
  2. As a salt combined with lithium tantalate, the crystals of this material have beneficial effects in selective audio signal damping and signal quality improvement.
  3. As a pure metal, it offers high corrosion resistance, high tensile strength, high ductility, and one of the highest high-temperature resilience among metals.
  4. As an alloying agent, tantalum can enhance the ductility, toughness, and elasticity of otherwise less tractable metals.
  5. Also, as an alloying agent, the metal can create superalloys in combination with metals of far lower cost, achieving sufficient pure metal properties in some regards without carrying the extreme cost burden of the pure metal.

What Are the Limitations of Tantalum?

Tantalum has a variety of limitations that affect its applicability to tasks, including:

  1. The high-purity metal is among the most expensive metals that are used commercially. It costs $310 per kg, compared with other metals such as chromium at $12–14 per kg, or nickel at $20 per kg.
  2. The processing of tantalum requires highly specialized equipment as its melting point is in excess of 3,000 °C and its processing temperatures are in the range of 2,000–3,000 °C.
  3. Tantalum has a marked sensitivity to fluoridated chemistries such as hydrofluoric acid. Contact with such chemistry can cause tantalum to dissolve, although this could be regarded as a very narrow and specific restriction on its use.

What Are the Effects of Tantalum in the Environment?

The mining and processing of tantalum, as with many other mineral resources, has significant environmental impacts.

Mining generally involves clearing large areas of forests and natural habitats. This results in the loss of biodiversity and disruption of ecosystems, soil erosion, waterway and groundwater contamination, and mineral and toxic chemical distribution through dust plumes and tailings. Additionally, tantalum mining and processing operations are energy-intensive. The consumption of fossil fuels both in extraction and smelting results in carbon emissions. Finally, profits from tantalum mining, along with other high-value metals, affect the human environment. Too often these operations add to conflict financing, particularly in central Africa where much of the most accessible tantalum reserves lie.

Responsible sourcing initiatives and certification programs such as the "Conflict-Free Smelter" program or the OECD Due Diligence Guidance for Responsible Supply Chains encourage responsible sourcing.

The recycling of bulky tantalum-containing apparatus and engine components is a well-established process, as the sources tend to be relatively large and easily identified. By weight, among the largest uses of the metal is in capacitors—used in virtually all electronics. These diffuse and disorderly sources are much harder to process for metal residues, and the great majority of e-waste is either poorly processed for gold or essentially destined for landfill.

Summary

This article presented tantalum, explained it, and discussed its characteristics and applications. To learn more about tantalum, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

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Xomety X
Team Xometry
This article was written by various Xometry contributors. Xometry is a leading resource on manufacturing with CNC machining, sheet metal fabrication, 3D printing, injection molding, urethane casting, and more.