Niobium in Superconductors: Why It Matters and How It Works

If you work with magnets, medical machines, or research tools, you have likely come across niobium. Niobium is used in the construction of superconductors which conduct electricity without loss. This guide describes what niobium is, why it is so effective, and where you will find it used today.

What Is Niobium?

Niobium is a metal. It has the symbol Nb. You find niobium in the ground in an ore called columbite. Miners get most of it from Brazil, Canada, and Australia. Small amounts also come from Nigeria and the Democratic Republic of Congo.

Niobium has a very high resistance to high temperature. It melts at 2,468°C. That’s hotter than most metals, such as iron and copper. It is also resistant to rust and remains durable even in cold conditions. Niobium reacts with air to create a thin layer on its surface. It is protected from breakdown by this layer. This renders niobium a safe material for use in machines that operate continuously for years.

When compared to other strong metals, niobium is soft and easily formed. It can be thin-wired or rolled into flat sheets by workers. This is very important in the case of superconductors, because the wire must bend around coils without breaking.

Niobium is not so uncommon. It is available in reasonable quantities in the soil. However, special processing is required to turn the raw niobium into the pure metal, such as melting it in a vacuum to remove dirt and gas. That’s why it is more expensive than common metals such as steel, even though it’s not difficult to find raw ore.

Why Titanium Also Matters in This Alloy

Niobium-titanium is not a pure form of niobium. Titanium comprises 40% to 60% of the mixture, and thus has a similar importance. Titanium is light, strong and even more corrosion resistant than niobium. When added to niobium, it makes a wire that is more flexible to bend and pull into thin wires than pure niobium.

Another benefit of titanium is its ability to manage costs. As titanium is easier to mine and process than niobium, the use of a titanium-rich alloy ensures that the wire is not prohibitively expensive, while maintaining good superconductivity.

Ti-Better supplies pure titanium rod and titanium wire as well, used in many industries beyond superconductors, including medical implants, aerospace parts, and chemical processing equipment. For more complete specs on standard grades of titanium, such as Gr1, Gr2, and Gr5, refer to the titanium rod page and the titanium wire page.

What Is a Superconductor?

If you ask what is superconductor material, the answer is simple: it conducts electric current without any loss.  As current passes through normal wires, some of the power is lost due to heat. That’s why your phone charger gets warm. Superconductors do not lose power in this manner. However, there’s a problem: they need to be cooled down a lot before that.

All super-conductors have a specific cold point. It is a superconductor below that temperature. Up there, it’s just like any other wire and dissipates power as heat. This is a cold point known as the critical temperature.

The niobium superconducting temperature is around 9 Kelvin for plain Nb. That’s almost -264°C, which is colder than outer space, in many places! It is possible to increase this “cold point” slightly by adding other metals to the niobium. This is beneficial when actually using the material in real machines, because you don’t have to use extreme cooling.

Magnets are also repelled by superconductors. When a magnet is brought close to a cold superconductor, the magnet will hover above the superconductor. This is termed the Meissner effect. This effect is useful for the engineers to create powerful magnets such as particle accelerators and MRI scanners, which require strong and stable magnetic fields.

Niobium is called a Type II Superconductor. This means it lets some magnetic flux pass through while it stays superconducting. This is unlike Type I superconductors, which cease to be superconductive when a strong magnetic field comes into contact with them. This is another advantage of niobium in the manufacture of high-power magnets.

Why Do Engineers Use Niobium for Superconductors?

The question may arise, why not use another metal? Why niobium is special.

• It is capable of resisting strong magnetic fields. Many metals stop being superconductors when a strong magnet is nearby. Niobium does not get affected by strong magnetic fields. This makes it ideal for large magnets in hospitals and laboratories where the magnetic field may be many times the normal magnet.
• It is flexible and not brittle. There are materials of superconductors that are difficult to handle and brittle. Niobium is malleable enough to be twisted into wire. It can be drawn, rolled and formed easily, even to very fine strands.
• It is long-lasting. After construction of one machine with niobium, it can continue to operate for decades. The niobium from years ago is still used in many of the MRI machines in hospitals, and there is no decrease in the efficiency of the machines.
• Works with factory tools. Niobium can be used in the normal metal-making process. This means that niobium wire can be manufactured in large quantities by factories without the need of special new tools and expensive equipment changes.
• It holds current well under stress. During processing, if small amounts of other material are added to niobium, tiny flaws are created within the metal. These defects actually aid in maintaining the magnetic field in the wire. This ensures that the flow of current does not get disrupted even when there is strong magnetic pull.

Types of Niobium Used in Superconductors

There are three main forms of niobium used for superconductors. Each one works best for a different job, based on cost, strength, and ease of use.

Niobium-Titanium (NbTi)

This niobium titanium alloy makes a niobium titanium superconductor.  Most NbTi has 40% to 60% titanium in it. It becomes a superconductor at around 10 K, just above that of niobium.

The niobium titanium superconductor (NbTi) is the world’s most widely-used superconductor metal. It is used in factories to be stacked into wires, pulled thin, and heated at a predetermined temperature to fix the superconductor structure. This wire can be used in MRI machines and research magnets around the world and can withstand fields up to approximately 15 Tesla.

Ti-Better produces niobium titanium rod, depending on the demand, the titanium content can be adjusted to 20%, 40%, 60%. Each batch is tested in the lab to ensure the mix is kept in a narrow range. You can check the niobium titanium rod page for full details on sizes and specs. Ti-Better also offers niobium titanium wire for other magnet and coil applications.

Niobium-Tin (Nb₃Sn)

This mix uses niobium and tin to make a niobium tin superconductor.  It starts working at a higher point than NbTi, about 18 Kelvin. It also can withstand the effects of even stronger magnetic field strengths, in some cases above 25 Tesla.

However, it is more difficult to work with Nb₃Sn. It is easily fractured, which requires care on the part of factories at all stages. A particular technique is employed: the workers wrap tin around the niobium and then heat the whole thing later. This makes it a powerful superconductor, without causing any damage. Builders need to plan the shape of the wire before the final heat step, otherwise it can crack and fail to function.

Nb₃Sn is found in the largest and strongest magnets, such as those in fusion energy research and in the top research laboratories, where the additional strength of the magnet is of critical importance.

Pure Niobium

Sometimes, engineers use niobium with no other metal mixed in. This form has the lowest cold point of the three, ~9 Kelvin, and it is the weakest of the three fields.

Pure niobium is the best choice if you require very pure and clean material. It is used in components of particle accelerators and in a few quantum computers, where a speck of dirt or other metal can be a problem. Factories melt this niobium in a vacuum to remove gas trapped inside the metal.

Where Is Niobium Superconductor Used?

Hospitals and MRI Machines

Every time a patient goes through an MRI scan, niobium is at work. NbTi wire is wrapped in coils in MRI machines. These coils make strong, steady magnetic fields, usually between 1.5 and 3 Tesla. This allows physicians to obtain clear images of the inside of the body without opening it up.

If there were no niobium, MRI machines would require a lot of electricity to operate and would become extremely hot. Niobium allows the machine to operate all day long with significantly less energy because once it is running the current flows through the coil without loss.

Particle Accelerators

A particle accelerator is a large science laboratory that is used to investigate the properties of tiny particles of matter. The magnets must be more powerful than any other type of magnet in these machines. One of the largest machines ever constructed, the Large Hadron Collider (LHC), has more than 1,600 magnets constructed from NbTi wire, each designed to steer fast-moving particles around the 27-kilometer circumference of the ring.

These magnets would not be as powerful as they are to bend particles around the huge circle in these laboratories without niobium wire. If the magnets were made of normal copper wire, they would require a lot of power to operate, which would not be feasible.

Fusion Energy Research

Researchers are attempting to create machines that replicate the sun’s energy here on Earth. This is known as fusion energy. These machines must contain very hot gas in a strong magnetic field, because nothing solid can come in contact with gas that hot. Niobium tin superconductor wire is a major part of this, as it can resist very strong fields required to keep the hot gas contained and stable.

Quantum Computers

New computers called quantum computers use tiny parts called qubits. The qubits are typically placed on a thin film of niobium. The niobium has to be cold and clean so that the qubit operates properly, otherwise the slightest imperfection will result in a mistake in the computer’s calculations. As quantum computers become larger, with companies seeking to create machines containing thousands of qubits, so will the demand for high-quality niobium.

Research Labs

Many university and government labs use niobium magnets to study new materials. The strong magnetic fields of these magnets are useful to scientists to study the behavior of various materials when they are subjected to stress, cold, or strong magnetic force. This work can often result in new discoveries that will be used in industry later.

Good Points of Using Niobium

Niobium has proven to be a time-tested material. Machines built decades ago with niobium parts still work today. This is evidence that it lasts for years and years, even if it is operated virtually continuously.

There is also guaranteed supply. The process of producing niobium wire is known, as the factories have been producing it for many years. This translates to less error and consistent quality, batch by batch.

Compared to newer types of superconductors, niobium costs less overall. However, newer materials might require special handling and higher costs, although they offer greater cold points. With all of the factors taken into account, niobium is often the better choice for a project.

Niobium is also easily bent. Unlike other superconductor metals, you will not have to worry about its snap during setup, which saves time and reduces the chances of costly mistakes on site.

Problems With Niobium Superconductors

Not everything is perfect and niobium has its own disadvantages.

• Very cold temperatures are required. Niobium is only effective below approximately 10K. For this, you must have liquid helium. This requires investment and proper equipment to maintain the cold, such as tanks and pipes which are specially designed for the purpose.
• The wire costs a lot. The production of pure niobium wire is not economical. This wire is used to construct a large magnet that can cost millions of dollars, when you include the parts and the cooling system.
• Nb₃Sn is fragile. This type may crack when not handled carefully. When using it for making magnets, workers need to be careful at each stage of the process, as a single mistake can result in the loss of an expensive batch of wire.
• Training issues. The initial start-up of a new superconducting magnet might not have as much current as expected. This stabilizes after a few attempts, but may slow down setup and testing time.
• Quench risk. In some cases, a superconductor suddenly ceases to be a superconductor and reverts to a normal wire. This is known as a quench. It has a very rapid release of heat. To prevent damage to the coil or other parts, machines require safety systems to detect this.

What’s Next for Niobium Superconductors

Researchers continue to work on the development of niobium wire. They are discovering improved methods of heating and forming NbTi to carry more current without the additional expense.

The groups are developing new ways to make Nb₃Sn less prone to cracking when it is set up. This may make the use of it in the future cheaper and easier, and increase the number of projects requiring very strong magnets.

Some labs are now mixing niobium magnets with newer types of superconductors. This blend can reduce the amount of liquid helium required, which will save money in the long run and preserve the strong field niobium is famous for.

The current most promising field of growth is quantum computing. With the growth of the number of qubits, companies will require more niobium in the future, and steady demand is expected for many years to come.

Frequently Asked Questions

What is the difference between niobium titanium superconductor (NbTi) and Nb₃Sn?

NbTi is bendable, cheaper, but Nb₃Sn can be used at a higher cold point and at higher magnetic fields.

Why does Nb require such low temperatures?

Niobium only becomes superconductive at temperatures below approximately 9 to 10K. This cold point is achieved by using the liquid helium.

Would niobium be suitable for use at room temperature?

Niobium is always a superconductor in the presence of deep cold. With today’s science, there is no way to get around this.

What is the life of niobium superconductor wire?

If stored cold and handled properly, it can have a long shelf life of decades. Numerous machines are still operating today with wire in place that was put in years ago.

What occurs when a quench occurs?

The wire quickly becomes non-superconductive and starts to heat up rapidly. This heat is safely released by safety systems to protect the machine.

Is a superconducting magnet very power consuming?

No. It then consumes very little power once started because the wire is carrying current without any loss. The bulk of the expense is incurred in maintaining its coldness.

What is the source of the niobium titanium rod or wire?

Ti-Better offers both niobium titanium rod and niobium titanium wire, each to your project’s exact specifications, tested in the lab on every batch.

Conclusion

Niobium’s role in today’s science and medicine is significant. It aids in the MRI scanning of patients, it aids in the study of tiny particles in labs and will soon be used in fusion energy plants. It’s important to make the right choice when it comes to niobium titanium rod or wire suppliers for your next project.

Ti-Better can fabricate the material to your specifications whether you need it as niobium titanium rod, niobium titanium wire, or standard titanium rod, titanium wire or titanium plate for other projects. Call Ti-Better today, to speak with you about your needs.