What type of superconductor is NbN?

Niobium nitride is a high-performance multifunctional material with extremely high thermal stability, electrical insulation and chemical stability, which has potential industrial applications.

Physical and chemical properties of niobium nitride

Density: 8.4

Melting point: 2573ºC

Molecular formula: NNb

Molecular weight: 106.91300Appearance: light gray slightly yellowMohs hardness: 8Microhardness: 14. 3GPaResistivity: 200u. cm

Typical B-1 compound. Sodium chloride crystal structure. The superconducting critical temperature is 17.3K. The upper critical magnetic field is 43T. The critical current density Jc, (4.2K, 20T) is as high as 2×106A/cm2. High thermal stability and chemical stability, anti-neutron radiation, excellent superconducting thin film material. It is prepared by sputtering in argon and nitrogen mixed gas. Used to make highly stable superconducting quantum devices. 

Niobium Nitride Stability

When heated to 500-800°C in air, it will generate niobium pentoxide and release nitrogen at the same time. Niobium nitride decomposes in vacuum to form niobium metal. Niobium nitride and titanium carbide, zirconium carbide, vanadium carbide, tantalum carbide, etc. can form a solid solution.

Preparation of niobium nitride

1. Using metal niobium and nitrogen as raw materials, send crushed metal niobium into a nitriding furnace, feed nitrogen or ammonia gas, and make it react at 700-1100°C to directly synthesize niobium nitride. Or add carbon powder to the pulverized metal niobium powder, make it fully mixed and send it into the reduction furnace, then pass in hydrogen and nitrogen, and reduce it at 1250°C for 2 hours to obtain niobium nitride.

2. Direct Method  Niobium nitride is prepared from metal niobium and nitrogen gas, and the reaction formula is as follows.Nb2O5+2N+5C→2NbN+5CO

Send the pulverized metal niobium into the nitriding furnace, feed nitrogen or ammonia gas, and make it react at 700-1100°C for 1-2 hours to obtain niobium nitride.

3. Reduction Method  In the presence of carbon, niobium nitride is prepared with niobium pentoxide and nitrogen as raw materials. The reaction formula is as follows.

Nb+N→NbN

Add carbon powder to the pulverized metal niobium powder, make it fully mixed, and then send it into the reduction furnace, then pass in hydrogen and nitrogen, and reduce it at a temperature of 1250 ° C for 2 hours to obtain niobium nitride.

Structure and Properties of Niobium Nitride

The structure of niobium nitride is composed of a lattice with interatomic covalent bonds and non-covalent bonds, in which the interatomic covalent bonds exist in the structure of niobium nitride in the form of rings and triangles, while the non-covalent bonds exist in the form of linear and plane composition. Due to its unique lattice structure, Niobium Amide has good thermal stability, electrical insulation and chemical stability, and can effectively resist environmental factors such as high temperature, acidity and oxidation, and its heat resistance to high temperature has been widely studied . In addition, the structure of niobium nitride also has a great influence on its mechanical properties, such as hardness, elastic modulus, compressive strength, etc.

In summary, niobium nitride has excellent thermal stability, electrical insulation and chemical stability, and has good mechanical properties, so it can be widely used in electronics, aerospace, energy, chemical industry, and automobiles.

Superconducting Properties of Niobium Nitride

As a superconducting material, niobium nitride is widely used in various superconducting devices, including superconducting nanowire single-photon detectors, Josephson junctions, fast single-flux quantum circuits, and thermal electron radiators. The composition of niobium nitride is very complex, not only there are various crystal structures, but also there are different ratios of niobium to nitrogen in the same crystal structure. The superconductivity of NbNx depends on its crystal structure and composition. Studies have shown that the change of composition will change the lattice constant value of niobium nitride. In materials with less nitrogen than niobium, the sublattice of nitrogen is defective. In materials with less niobium than nitrogen, the sublattice of niobium is defective. The lattice has defects. The composition of niobium and nitrogen determines the crystal phase and lattice constant of the film at the same time, and then affects the superconducting properties of the niobium nitride film.