Niobium-tin (Nb3Sn) Nb3Sn

Nb₃Sn · CAS 12035-04-0 · cubic A15

Niobium-tin (Nb3Sn) is an intermetallic superconductor with the A15 crystal structure.

9 sources · Updated 2026-10-26 · CC BY 4.0

Evidence level

2 of 5

Lab-measured

Field

24 to 26.5 T

Temperature

18.3 K

Cryogenic operation

4 K

Recipe, share of the weight

Nb not statedNiobium
Sn not statedTin

Best for

Superconducting magnets at about 11 to 13 T and 4 K, where NbTi cannot carry the needed current density (ITER central solenoid designed for 13 T)

Weakest at

Brittleness and strain: large strain causes irreversible cracking of the A15 layer, and the critical current of present conductors falls off swiftly above 12 to 15 T (PRM 2024). The fine powder is also a flammable solid (supplier SDS).

Risk at a glance

People None found. Flammable fine powder; the supplier sheet classes the…
If it fails High. Cracking of the A15 layer under large strain
Corrosion No data. No corrosion data recorded

Quick facts: Nb3Sn

Key properties of Nb3Sn
Property	Value	Basis
Melting point	2,100 °C	1 sourced value

What is the melting point of Niobium-tin (Nb3Sn)?

Niobium-tin (Nb3Sn) has a melting point of 2,100 °C. The source and test conditions are listed in the properties table on this page.

What is Niobium-tin (Nb3Sn) used for?

Uses recorded in the sources include Toroidal-field and central-solenoid magnets of ITER; Quadrupole magnets for the High-Luminosity LHC at CERN.

Why it exists

Niobium-tin is an A15 intermetallic superconductor. Superconductivity was found shortly after that of V3Si, the first A15 superconductor. Its interest is that it carries very large current densities at fields beyond the reach of NbTi, which is the usual workhorse for large superconducting magnets. The trade is brittleness: the A15 layer is hard and cracks under large strain, so the wire has to be handled and supported with care.

Where it's used

Fusion magnets (ITER)

ITER's toroidal-field coils reach a maximum field of 11.8 T and its central solenoid 13 T. The magnets are wound from Nb3Sn cable and NbTi, and they are cooled to about 4 K with supercritical helium.

Accelerator magnets (HL-LHC)

CERN reports that Nb3Sn lets the High-Luminosity LHC quadrupoles reach fields as high as 11.5 T, compared with the current LHC design.

Recipe

Nb₃Sn

Nb3Sn is a binary intermetallic compound: three niobium atoms for each tin atom, with the tin on a body-centred cubic sublattice and the niobium in chains. The review notes that the A15 phase forms by solid-state diffusion reactions between niobium and tin.

What Nb3Sn is made of
Ingredient	Share of the weight	What it does
Niobium Nb	not stated	Forms chains of niobium atoms. The review links the short Nb to Nb spacing in these chains to the high critical temperature.
Tin Sn	not stated	Sits on the body-centred sublattice. The tin fraction controls Tc and Hc2: both fall as the A15 phase becomes tin-deficient.

Weight shares are as printed in the sources.

What it can do

Field

24 to 26.5 T

measured

State-of-the-art Ta- and Ti-doped strands reach an upper critical field of about 24 to 26.5 T at 4.2 K. Extrapolated to 0 K, the highest-tin ternary wires reach about 29 T.

Temperature

18.3 K

measured

The highest critical temperature reported is 18.3 K. A near-stoichiometric thin film has a Tc(0) of close to 18 K.

Cryogenic operation

4 K

ITER cools its Nb3Sn and NbTi magnets with supercritical helium at about 4 K.

How it compares

Nb3Sn carries very large current densities at fields far beyond the limits of NbTi, the commonly used superconductor for large magnets, and it is the material used for ITER's highest-field coils. The price is brittleness: large strain cracks the A15 layer. Its highest reported critical temperature of 18.3 K is above the 16 K and 10.5 K that the review gives for disordered thin films.

The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details. Compare every grade in the family.

Benchmarks
Measurement	Nb3Sn
Thermal behavior and safety
Melting point (supplier product sheet)	2100 °C¹²
Temperature behavior
Critical temperature, highest value reported for Nb3Sn	18.3 K¹
Critical temperature Tc(0), near-stoichiometric thin film	18 K²
Critical temperature Tc(0), optimally dirty thin film	16 K³
Critical temperature Tc(0), disordered thin film	10.5 K⁴
Critical temperature Tc(0), upper phase boundary for ternary wires	18 K⁵
Cryogenic operating temperature of Nb3Sn magnets	4 K¹³
Other measurements
Upper critical field, upper phase boundary for ternary wires	29 T⁶
Upper critical field, near-stoichiometric thin film	26.5 T⁷
Upper critical field, optimally dirty thin film	29 T⁸
Upper critical field, disordered thin film	15 T⁹
Upper critical field of state-of-the-art wire at 4.2 K	24 to 26.5 T¹⁰
Lattice parameter of the A15 cell	0.529 nm¹¹
Tin content range of the A15 phase	18 to 25 at.% Sn¹⁴

Why choose it, and why not

Good for

High-field magnets at 4 K. ITER's central solenoid is designed for a maximum field of 13 T.
High critical temperature for a superconductor: 18.3 K is the highest reported for Nb3Sn.

Watch out for

Brittleness. Large strain cracks the A15 layer irreversibly.
Critical current falls off swiftly above about 12 to 15 T for present conductors.
Tin deficiency and disorder lower Tc and Hc2 sharply in thin films.

Nb3Sn is the superconductor chosen for ITER's highest-field coils and for the HL-LHC quadrupoles. It is brittle and must be kept free of large strain, and the sources read here do not answer its corrosion or oxidation behaviour in air.

Technical details

For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.

Notes

The method, full conditions and any caveat for the numbered rows above.

Notes for the numbered rows
#	Measurement	Method	Conditions	Caveat
1	Critical temperature, highest value reported for Nb3Sn	Value stated in the review, which attributes it to Hanak et al. (1964)	form A15 Nb3Sn, highest value reported in the literaturereference year 1964	—
2	Critical temperature Tc(0), near-stoichiometric thin film	Review text says the film has a Tc(0) of close to 18 K; the value is a fitted extrapolation	form thin film, residual resistivity 9 µΩcm, 24.8 at.% Sn (close to stoichiometric)temperature 0 K, extrapolated	—
3	Critical temperature Tc(0), optimally dirty thin film	Printed as about 16 K in the review's thin-film discussion; extrapolated to 0 K	form thin film, residual resistivity 35 µΩcm, 23.6 at.% Sntemperature 0 K, extrapolated	—
4	Critical temperature Tc(0), disordered thin film	Printed as about 10.5 K in the review's thin-film discussion; extrapolated to 0 K	form thin film, residual resistivity 70 µΩcm, 21 at.% Sntemperature 0 K, extrapolated	Shows how strongly Tc falls with tin deficiency and disorder; not a wire value.
5	Critical temperature Tc(0), upper phase boundary for ternary wires	Review concludes that the highest Sn fractions in wires represent an upper phase boundary of about 18 K; not a single measured sample	form ternary wires with the highest tin fractiontemperature 0 K, extrapolated	—
6	Upper critical field, upper phase boundary for ternary wires	Printed as about 29 T in the review; an extrapolated upper phase boundary rather than a single measured sample	form ternary wires with the highest tin fractiontemperature 0 K, extrapolated	—
7	Upper critical field, near-stoichiometric thin film	Printed as about 26.5 T in the review; reduced compared with the disordered film, and extrapolated	form thin film, residual resistivity 9 µΩcm, 24.8 at.% Sntemperature 0 K, extrapolated	Thin film, not a bulk wire; the review says the near-stoichiometric film has a reduced Hc2(0) at a Tc(0) of close to 18 K.
8	Upper critical field, optimally dirty thin film	Printed as about 29 T in the review's thin-film discussion; extrapolated	form thin film, residual resistivity 35 µΩcm, 23.6 at.% Sntemperature 0 K, extrapolated	—
9	Upper critical field, disordered thin film	Printed as about 15 T in the review's thin-film discussion; extrapolated	form thin film, residual resistivity 70 µΩcm, 21 at.% Sntemperature 0 K, extrapolated	—
10	Upper critical field of state-of-the-art wire at 4.2 K	Range printed in the paper's introduction for state-of-the-art doped strands at 4.2 K	form state-of-the-art Ta- and Ti-doped Nb3Sn strandstemperature 4.2 K	—
11	Lattice parameter of the A15 cell	Value printed as about 0.529 nm for the stoichiometric composition in the review	composition stoichiometric A15 Nb3Sn	—
12	Melting point (supplier product sheet)	Supplier safety data sheet value; the test method is not stated	form niobium tin powder, supplier product (American Elements, CAS 12035-04-0)	Supplier value for a commercial powder; check against a primary reference before use in design.
13	Cryogenic operating temperature of Nb3Sn magnets	ITER describes its Nb3Sn and NbTi magnets as cooled with supercritical helium in the range of 4 Kelvin	coolant supercritical helium	—
14	Tin content range of the A15 phase	Converted by Space Mushroom from beta = 0.18 to 0.25 (multiplied by 100); the review gives the A15 stability range as 0.18 to 0.25	unit in source beta, atomic fraction of Sn, 0.18 to 0.25	—

Risks and side effects

Hazards to people, what happens when a cell overheats, and how the material is handled and stored.

For people

The supplier classes the fine powder as a flammable solid and irritant, and says the acute and chronic toxicity of the substance is not fully known.

The powder: The supplier classifies the powder as a flammable solid (H228) that causes skin irritation, serious eye irritation and respiratory irritation (H315, H319, H335).
In a fire: The supplier advises a special powder for metal fires and says water is unsuitable.
Tin exposure: The supplier prints a USA exposure limit of 2 mg/m3 for tin compounds, measured as Sn.

In operation

Strain: A wire that is strained too far is damaged irreversibly, because the A15 layer cracks. Strain comes from thermal contraction differences and magnetic forces in a magnet.
High field: The critical current of present Nb3Sn conductors falls off swiftly above about 12 to 15 T.

Handling and storage

Storage: Keep containers tightly sealed in a cool, dry, well-ventilated place, away from oxidising agents and protected from electrostatic charge.
Transport: The supplier gives the transport class as flammable solid, UN3089, packing group III.

Test details
The original wording and numbers from the sources, for readers who want them.

Failure risks

Failure risks
Failure	Trigger and consequence
Cracking of the A15 layer under large strainhigh severity	Large strain in the composite wire, from thermal-contraction differences and Lorentz forces in a magnetSerious and irreversible damage to the superconductor, in the form of cracks in the brittle A15 material
Falling critical current at high fieldmoderate severity	Operation above about 12 to 15 TThe critical current density of present Nb3Sn conductors declines swiftly above 12 to 15 T, so higher fields need better vortex pinning (PRM 2024)
Loss of superconducting performance with tin deficiencymoderate severity	A15 phase with about 21 at.% Sn and high residual resistivity (70 µΩcm thin film)Tc(0) falls to about 10.5 K and Hc2(0) to about 15 T in the disordered film, against about 18 K and 26.5 T for the near-stoichiometric film

Handling and storage

Keep containers tightly sealed in a cool, dry, well-ventilated place. Protect against electrostatic charges and store away from oxidising agents.

Supply and geography

How common the raw materials are and where they come from.

Niobium

Top producers (2025): Brazil 92.9%, Canada 5.4%, Russia 0.3%, Congo (Kinshasa) 0.9%
Critical mineral lists: US: listed, EU: listed
Recycling: USGS: niobium was recycled when niobium-bearing steels and superalloys were recycled; scrap recovery for niobium content was negligible, and total recycling may have been as much as 20% of apparent consumption.
Substitutes: USGS: ceramic matrix composites, molybdenum, tantalum and tungsten can replace niobium in high-temperature superalloys, with a performance loss or higher cost. For superconducting wire, NbTi is the present workhorse (godeke2006), and Nb3Sn is the higher-field alternative.

Tin

Top producers (2025): China 24.5%, Indonesia 21%, Peru 11.4%, Brazil 9.7%, Bolivia 5.2%
Critical mineral lists: US: listed, EU: not listed
Recycling: USGS tin chapter: about 17,000 tons of tin from old and new scrap was estimated to have been recycled in 2025.

Documents

Datasheets, safety data sheets, papers and standards you can open.

Documents
Document	Type	Year
American Elements: Niobium tin (CAS 12035-04-0), safety data sheet and product page	sds	2026
A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State (arXiv:cond-mat/0606303)	paper	2006
Influence of Nb alloying on Nb recrystallization and the upper critical field of Nb3Sn (accepted manuscript, Phys. Rev. Materials 8, 084801)	paper	2024
USGS Mineral Commodity Summaries 2026: Niobium (Columbium)	report	2026
USGS Mineral Commodity Summaries 2026: Tin	report	2026

Full record

The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.

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spore: profile
id: nb3sn
spore_version: 0.2
family: magnet-and-superconducting-alloys
name: Niobium-tin (Nb3Sn)
abbreviation: Nb3Sn
role: A15 superconductor wire for high-field magnets
category: metals
type: refractory-metals
summary: |
  Niobium-tin (Nb3Sn) is an intermetallic superconductor with the A15 crystal structure. The highest critical temperature reported for it is 18.3 K (Hanak et al., 1964, quoted in a 2006 review). Its upper critical field, extrapolated to 0 K, is about 29 T for the highest-tin ternary wires in the review. State-of-the-art Ta- and Ti-doped strands reach about 24 to 26.5 T at 4.2 K (Physical Review Materials, 2024). ITER's toroidal-field and central-solenoid magnets use Nb3Sn cable, and CERN reports that Nb3Sn will allow the HL-LHC quadrupoles to reach fields as high as 11.5 T.
best_for: Superconducting magnets at about 11 to 13 T and 4 K, where NbTi cannot carry the needed current density (ITER central solenoid designed for 13 T)
weakest_at: 'Brittleness and strain: large strain causes irreversible cracking of the A15 layer, and the critical current of present conductors falls off swiftly above 12 to 15 T (PRM 2024). The fine powder is also a flammable solid (supplier SDS).'
identity:
  formula: Nb3Sn
  cas: 12035-04-0
  crystal_system: cubic A15 (A3B type, Sn atoms on a bcc sublattice)
  source: ae-nb3sn
  where: Section 3.1 (CAS 12035-04-0, Niobium tin powder) and Chemical Identifiers (linear formula Nb3Sn, PubChem CID 15251588); crystal structure from godeke2006, text on the A15 lattice and the cubic and tetragonal phases
tags:
  environments: []
  stresses:
    - extreme-cold
  applications:
    - electronics-and-chips
properties:
  - benchmark: critical_temperature
    label: Critical temperature, highest value reported for Nb3Sn
    value: 18.3
    unit: K
    scope: material
    conditions:
      form: A15 Nb3Sn, highest value reported in the literature
      reference_year: 1964
    method: Value stated in the review, which attributes it to Hanak et al. (1964)
    status: ground
    source: godeke2006
    where: Introduction, first paragraph (sentence beginning 'Its highest reported critical temperature')
  - benchmark: critical_temperature
    label: Critical temperature Tc(0), near-stoichiometric thin film
    value: 18
    unit: K
    scope: material
    conditions:
      form: thin film, residual resistivity 9 µΩcm, 24.8 at.% Sn (close to stoichiometric)
      temperature: 0 K, extrapolated
    method: Review text says the film has a Tc(0) of close to 18 K; the value is a fitted extrapolation
    status: calculated
    source: godeke2006
    where: Section V, text on the film results with varying resistivity (Hc2(T) of thin films)
  - benchmark: critical_temperature
    label: Critical temperature Tc(0), optimally dirty thin film
    value: 16
    unit: K
    scope: material
    conditions:
      form: thin film, residual resistivity 35 µΩcm, 23.6 at.% Sn
      temperature: 0 K, extrapolated
    method: Printed as about 16 K in the review's thin-film discussion; extrapolated to 0 K
    status: calculated
    source: godeke2006
    where: Section V, text on the film results with varying resistivity (Hc2(T) of thin films)
  - benchmark: critical_temperature
    label: Critical temperature Tc(0), disordered thin film
    value: 10.5
    unit: K
    scope: material
    conditions:
      form: thin film, residual resistivity 70 µΩcm, 21 at.% Sn
      temperature: 0 K, extrapolated
    method: Printed as about 10.5 K in the review's thin-film discussion; extrapolated to 0 K
    status: calculated
    note: Shows how strongly Tc falls with tin deficiency and disorder; not a wire value.
    source: godeke2006
    where: Section V, text on the film results with varying resistivity (Hc2(T) of thin films)
  - benchmark: critical_temperature
    label: Critical temperature Tc(0), upper phase boundary for ternary wires
    value: 18
    unit: K
    scope: material
    conditions:
      form: ternary wires with the highest tin fraction
      temperature: 0 K, extrapolated
    method: Review concludes that the highest Sn fractions in wires represent an upper phase boundary of about 18 K; not a single measured sample
    status: calculated
    source: godeke2006
    where: Section V, paragraph on the upper phase boundary of wires (text beside the Hc2(T) fit)
  - benchmark: upper_critical_field
    label: Upper critical field, upper phase boundary for ternary wires
    value: 29
    unit: T
    scope: material
    conditions:
      form: ternary wires with the highest tin fraction
      temperature: 0 K, extrapolated
    method: Printed as about 29 T in the review; an extrapolated upper phase boundary rather than a single measured sample
    status: calculated
    source: godeke2006
    where: Section V, paragraph on the upper phase boundary of wires (text beside the Hc2(T) fit)
  - benchmark: upper_critical_field
    label: Upper critical field, near-stoichiometric thin film
    value: 26.5
    unit: T
    scope: material
    conditions:
      form: thin film, residual resistivity 9 µΩcm, 24.8 at.% Sn
      temperature: 0 K, extrapolated
    method: Printed as about 26.5 T in the review; reduced compared with the disordered film, and extrapolated
    status: calculated
    note: Thin film, not a bulk wire; the review says the near-stoichiometric film has a reduced Hc2(0) at a Tc(0) of close to 18 K.
    source: godeke2006
    where: Section V, text on the film results with varying resistivity (Hc2(T) of thin films)
  - benchmark: upper_critical_field
    label: Upper critical field, optimally dirty thin film
    value: 29
    unit: T
    scope: material
    conditions:
      form: thin film, residual resistivity 35 µΩcm, 23.6 at.% Sn
      temperature: 0 K, extrapolated
    method: Printed as about 29 T in the review's thin-film discussion; extrapolated
    status: calculated
    source: godeke2006
    where: Section V, text on the film results with varying resistivity (Hc2(T) of thin films)
  - benchmark: upper_critical_field
    label: Upper critical field, disordered thin film
    value: 15
    unit: T
    scope: material
    conditions:
      form: thin film, residual resistivity 70 µΩcm, 21 at.% Sn
      temperature: 0 K, extrapolated
    method: Printed as about 15 T in the review's thin-film discussion; extrapolated
    status: calculated
    source: godeke2006
    where: Section V, text on the film results with varying resistivity (Hc2(T) of thin films)
  - benchmark: upper_critical_field
    label: Upper critical field of state-of-the-art wire at 4.2 K
    value: 24
    value_high: 26.5
    bound: range
    unit: T
    scope: material
    conditions:
      form: state-of-the-art Ta- and Ti-doped Nb3Sn strands
      temperature: 4.2 K
    method: Range printed in the paper's introduction for state-of-the-art doped strands at 4.2 K
    status: ground
    source: prm2024
    where: Abstract, first paragraph (and Introduction, first paragraph)
  - benchmark: lattice_parameter
    label: Lattice parameter of the A15 cell
    value: 0.529
    unit: nm
    scope: material
    conditions:
      composition: stoichiometric A15 Nb3Sn
    method: Value printed as about 0.529 nm for the stoichiometric composition in the review
    status: ground
    source: godeke2006
    where: Text on the A15 structure beside figure 2 (next to the Nb-chain distance discussion)
  - benchmark: melting_point
    label: Melting point (supplier product sheet)
    value: 2100
    unit: °C
    scope: material
    conditions:
      form: niobium tin powder, supplier product (American Elements, CAS 12035-04-0)
    method: Supplier safety data sheet value; the test method is not stated
    status: ground
    note: Supplier value for a commercial powder; check against a primary reference before use in design.
    source: ae-nb3sn
    where: Section 9.1, row Melting point/Melting range
  - benchmark: operating_temperature
    label: Cryogenic operating temperature of Nb3Sn magnets
    value: 4
    unit: K
    scope: material
    conditions:
      coolant: supercritical helium
    method: ITER describes its Nb3Sn and NbTi magnets as cooled with supercritical helium in the range of 4 Kelvin
    status: ground
    source: iter-magnets
    where: Magnets page, opening paragraph
  - benchmark: a15_tin_range
    label: Tin content range of the A15 phase
    value: 18
    value_high: 25
    bound: range
    unit: at.% Sn
    scope: material
    conditions:
      unit_in_source: beta, atomic fraction of Sn, 0.18 to 0.25
    method: Converted by Space Mushroom from beta = 0.18 to 0.25 (multiplied by 100); the review gives the A15 stability range as 0.18 to 0.25
    status: ground
    source: godeke2006
    where: Introduction, paragraph on the Nb-Sn phase diagram (text beside figure 1)
corrosion: []
risks:
  hazards:
    - text: Supplier SDS classifies the niobium tin powder as a flammable solid (H228) that causes skin irritation (H315), serious eye irritation (H319) and may cause respiratory irritation (H335).
      ghs:
        - H228
        - H315
        - H319
        - H335
      source: ae-nb3sn
      where: Sections 2.1 and 2.2
    - text: In a fire, use special powder for metal fires. Water is listed as an unsuitable extinguishing agent. For transport the supplier gives UN3089, metal powder, flammable, n.o.s. (niobium tin powder), class 4.1, packing group III.
      ghs: []
      source: ae-nb3sn
      where: Sections 5.1 and 14
    - text: The supplier prints an exposure limit for tin metal, oxide and inorganic compounds as Sn of 2 mg/m3 (USA PEL). The limit is for tin, not for Nb3Sn specifically.
      ghs: []
      source: ae-nb3sn
      where: Section 8.1
  failure_risks:
    - mode: Cracking of the A15 layer under large strain
      trigger: Large strain in the composite wire, from thermal-contraction differences and Lorentz forces in a magnet
      consequence: Serious and irreversible damage to the superconductor, in the form of cracks in the brittle A15 material
      severity: high
      source: godeke2006
      where: Section on strain effects (text beside figure 11)
    - mode: Falling critical current at high field
      trigger: Operation above about 12 to 15 T
      consequence: The critical current density of present Nb3Sn conductors declines swiftly above 12 to 15 T, so higher fields need better vortex pinning (PRM 2024)
      severity: moderate
      source: prm2024
      where: Abstract, first paragraph
    - mode: Loss of superconducting performance with tin deficiency
      trigger: A15 phase with about 21 at.% Sn and high residual resistivity (70 µΩcm thin film)
      consequence: Tc(0) falls to about 10.5 K and Hc2(0) to about 15 T in the disordered film, against about 18 K and 26.5 T for the near-stoichiometric film
      severity: moderate
      source: godeke2006
      where: Section V, text on the film results with varying resistivity
  handling:
    - text: Keep containers tightly sealed in a cool, dry, well-ventilated place. Protect against electrostatic charges and store away from oxidising agents.
      source: ae-nb3sn
      where: Section 7.1 and 7.2
uses:
  - application: electronics-and-chips
    device: Toroidal-field and central-solenoid magnets of ITER
    example: ITER's magnets are made of Nb3Sn or NbTi superconductors; the toroidal-field coils reach a maximum field of 11.8 T and the central solenoid a maximum field of 13 T. Nb3Sn strand for these systems was produced by nine suppliers, 500 metric tonnes of strand in a procurement that ran from 2008 to 2015.
    source: iter-magnets
    where: Magnets page, Toroidal Field System, Central Solenoid, and the paragraph on strand procurement
  - application: electronics-and-chips
    device: Quadrupole magnets for the High-Luminosity LHC at CERN
    example: CERN Courier reports that Nb3Sn will allow the HL-LHC quadrupole magnets to reach fields as high as 11.5 T.
    source: cern-courier-2025
    where: Article body, paragraph on Nb3Sn magnet fields (dated 24 March 2025)
supply:
  - subject: Niobium
    producers:
      - country: Brazil
        share_percent: 92.9
        year: 2025
      - country: Canada
        share_percent: 5.4
        year: 2025
      - country: Russia
        share_percent: 0.3
        year: 2025
      - country: Congo (Kinshasa)
        share_percent: 0.9
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (entry 'Niobium, used to strengthen steel')
        listed: true
      - list: EU critical raw materials list (entry 'Niobium')
        listed: true
    recycling: 'USGS: niobium was recycled when niobium-bearing steels and superalloys were recycled; scrap recovery for niobium content was negligible, and total recycling may have been as much as 20% of apparent consumption.'
    substitutes:
      - 'USGS: ceramic matrix composites, molybdenum, tantalum and tungsten can replace niobium in high-temperature superalloys, with a performance loss or higher cost. For superconducting wire, NbTi is the present workhorse (godeke2006), and Nb3Sn is the higher-field alternative.'
    source: usgs-mcs2026-niobium
    where: 'World Mine Production and Reserves table, 2025e (world total 112,000 t; shares calculated by Space Mushroom from the table: Brazil 104,000 t, Canada 6,000 t, Russia 300 t, Congo (Kinshasa) 970 t). Recycling and Substitutes sections.'
  - subject: Tin
    producers:
      - country: China
        share_percent: 24.5
        year: 2025
      - country: Indonesia
        share_percent: 21
        year: 2025
      - country: Peru
        share_percent: 11.4
        year: 2025
      - country: Brazil
        share_percent: 9.7
        year: 2025
      - country: Bolivia
        share_percent: 5.2
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (entry 'Tin, used for food and beverage cans, circuit board components and corrosion-resistant metal coatings')
        listed: true
      - list: EU critical raw materials list (tin is not on the list)
        listed: false
    recycling: 'USGS tin chapter: about 17,000 tons of tin from old and new scrap was estimated to have been recycled in 2025.'
    substitutes: []
    source: usgs-mcs2026-tin
    where: 'World Mine Production and Reserves table, 2025e (world total 290,000 t; shares calculated by Space Mushroom from the table: China 71,000 t, Indonesia 61,000 t, Peru 33,000 t, Brazil 28,000 t, Bolivia 15,000 t). Recycling section.'
documents:
  - title: 'American Elements: Niobium tin (CAS 12035-04-0), safety data sheet and product page'
    type: sds
    url: https://www.americanelements.com/cas/12035-04-0
    year: 2026
  - title: A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State (arXiv:cond-mat/0606303)
    type: paper
    url: https://arxiv.org/pdf/cond-mat/0606303
    year: 2006
  - title: Influence of Nb alloying on Nb recrystallization and the upper critical field of Nb3Sn (accepted manuscript, Phys. Rev. Materials 8, 084801)
    type: paper
    url: https://link.aps.org/accepted/10.1103/PhysRevMaterials.8.084801
    year: 2024
  - title: 'USGS Mineral Commodity Summaries 2026: Niobium (Columbium)'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Tin'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tin.pdf
    year: 2026
gaps:
  - 'Density of Nb3Sn not found: the supplier sheet prints ''No data available'' and no other fetched source gives a value.'
  - No corrosion or oxidation-in-air data for Nb3Sn wire found. The searches turned up internal oxidation of Nb-Ta-Hf alloys used on purpose, and HF-based removal of the Ta barrier during processing, neither of which is an environmental corrosion result. The corrosion list is therefore empty.
  - No critical-current density (Jc) number at a stated field and temperature was read in a fetched page; the review's Jc results are in figures only. The Jc statement in this profile comes from the 2024 paper's qualitative sentence.
  - Wire heat-treatment (reaction) temperature and time were not read from a fetched page, so the process route is not described in the recipe line.
  - No UNS, EN, DIN, JIS or ASTM designation for the Nb3Sn compound was found in a fetched source. The supplier lists CAS 12035-04-0 and PubChem CID 15251588.
  - 'Non-canonical property names used because property-canon.yaml has no entry for them: critical_temperature, upper_critical_field, lattice_parameter, operating_temperature and a15_tin_range.'
  - Space application not found. The applications list has no magnets, fusion or accelerator category, so the ITER and HL-LHC uses are filed under electronics-and-chips as the nearest available tag. Please review that choice.
  - Upper critical field values at 0 K are extrapolations from the review's fits, and the 29 T upper boundary is for ternary wires, not a single sample.
  - Hf-alloying results (about 28 T and about 31 T, from the 2024 paper) are described there as so-far observations and are left out of the property rows.
  - Creep, fatigue and thermal-expansion data for Nb3Sn were not searched for in this run.
  - No image fetched, so the media list is empty.
sources:
  godeke2006:
    title: A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State
    id: arXiv:cond-mat/0606303
    url: https://arxiv.org/pdf/cond-mat/0606303
    year: 2006
    kind: paper
    license: arXiv (author-submitted preprint)
  prm2024:
    title: Influence of Nb alloying on Nb recrystallization and the upper critical field of Nb3Sn
    id: doi:10.1103/PhysRevMaterials.8.084801 (Phys. Rev. Materials 8, 084801, 2024; accepted manuscript on CHORUS)
    url: https://link.aps.org/accepted/10.1103/PhysRevMaterials.8.084801
    year: 2024
    kind: paper
    license: accepted manuscript (CHORUS)
  ae-nb3sn:
    title: 'American Elements: Niobium tin (CAS 12035-04-0), product page with safety data sheet'
    id: CAS 12035-04-0; PubChem CID 15251588
    url: https://www.americanelements.com/cas/12035-04-0
    year: 2026
    kind: datasheet
    license: supplier document, linked not reproduced
  iter-magnets:
    title: ITER Superconducting Magnets (ITER Machine Systems)
    id: ITER Organization, Magnets page
    url: https://www.iter.org/machine/magnets
    year: 2026
    kind: web
    license: ITER web content, cited not reproduced
  cern-courier-2025:
    title: CERN gears up for tighter focusing (CERN Courier, 24 March 2025)
    id: CERN Courier article
    url: https://cerncourier.com/a/cern-gears-up-for-tighter-focusing/
    year: 2025
    kind: web
    license: CERN Courier, cited not reproduced
  usgs-mcs2026-niobium:
    title: Mineral Commodity Summaries 2026, Niobium (Columbium)
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-tin:
    title: Mineral Commodity Summaries 2026, Tin
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tin.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-crit2025:
    title: About the 2025 List of Critical Minerals (USGS, final list of 60 minerals)
    id: Final 2025 List of Critical Minerals, November 2025
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
    kind: web
    license: public domain (USGS)
  ec-crm:
    title: Critical raw materials (European Commission, fifth list of 34 critical raw materials)
    id: EU critical raw materials list
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    year: 2024
    kind: web
    license: European Commission web page
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 14
  unreachable: 1
  caveats: 3
  note: Read by an AI assistant on 2026-10-26. verify-values found 13 of 14 values in their cited source text; the melting point (2100 °C) is on a JavaScript-rendered supplier page that the script cannot read, and was checked by reading the page in a browser in this run. Supply shares are calculated from the USGS production tables. Corrosion, density and Jc are left as gaps.
story:
  recipe:
    line: 'Nb3Sn is a binary intermetallic compound: three niobium atoms for each tin atom, with the tin on a body-centred cubic sublattice and the niobium in chains. The review notes that the A15 phase forms by solid-state diffusion reactions between niobium and tin.'
    parts:
      - name: Niobium
        symbol: Nb
        role: Forms chains of niobium atoms. The review links the short Nb to Nb spacing in these chains to the high critical temperature.
      - name: Tin
        symbol: Sn
        role: 'Sits on the body-centred sublattice. The tin fraction controls Tc and Hc2: both fall as the A15 phase becomes tin-deficient.'
  risk_groups:
    - title: For people
      level: 0
      verdict: Flammable fine powder; the supplier sheet classes the…
      lead: The supplier classes the fine powder as a flammable solid and irritant, and says the acute and chronic toxicity of the substance is not fully known.
      points:
        - label: The powder
          line: The supplier classifies the powder as a flammable solid (H228) that causes skin irritation, serious eye irritation and respiratory irritation (H315, H319, H335).
        - label: In a fire
          line: The supplier advises a special powder for metal fires and says water is unsuitable.
        - label: Tin exposure
          line: The supplier prints a USA exposure limit of 2 mg/m3 for tin compounds, measured as Sn.
    - title: In operation
      points:
        - label: Strain
          line: A wire that is strained too far is damaged irreversibly, because the A15 layer cracks. Strain comes from thermal contraction differences and magnetic forces in a magnet.
        - label: High field
          line: The critical current of present Nb3Sn conductors falls off swiftly above about 12 to 15 T.
    - title: Handling and storage
      points:
        - label: Storage
          line: Keep containers tightly sealed in a cool, dry, well-ventilated place, away from oxidising agents and protected from electrostatic charge.
        - label: Transport
          line: The supplier gives the transport class as flammable solid, UN3089, packing group III.
  why: 'Niobium-tin is an A15 intermetallic superconductor. Superconductivity was found shortly after that of V3Si, the first A15 superconductor. Its interest is that it carries very large current densities at fields beyond the reach of NbTi, which is the usual workhorse for large superconducting magnets. The trade is brittleness: the A15 layer is hard and cracks under large strain, so the wire has to be handled and supported with care.'
  uses:
    - where: Fusion magnets (ITER)
      line: ITER's toroidal-field coils reach a maximum field of 11.8 T and its central solenoid 13 T. The magnets are wound from Nb3Sn cable and NbTi, and they are cooled to about 4 K with supercritical helium.
    - where: Accelerator magnets (HL-LHC)
      line: CERN reports that Nb3Sn lets the High-Luminosity LHC quadrupoles reach fields as high as 11.5 T, compared with the current LHC design.
  can_do:
    - label: Field
      benchmark: upper_critical_field
      line: State-of-the-art Ta- and Ti-doped strands reach an upper critical field of about 24 to 26.5 T at 4.2 K. Extrapolated to 0 K, the highest-tin ternary wires reach about 29 T.
    - label: Temperature
      benchmark: critical_temperature
      line: The highest critical temperature reported is 18.3 K. A near-stoichiometric thin film has a Tc(0) of close to 18 K.
    - label: Cryogenic operation
      value: 4 K
      line: ITER cools its Nb3Sn and NbTi magnets with supercritical helium at about 4 K.
  compare: 'Nb3Sn carries very large current densities at fields far beyond the limits of NbTi, the commonly used superconductor for large magnets, and it is the material used for ITER''s highest-field coils. The price is brittleness: large strain cracks the A15 layer. Its highest reported critical temperature of 18.3 K is above the 16 K and 10.5 K that the review gives for disordered thin films.'
  compare_rows:
    - label: Highest critical temperature
      benchmark: critical_temperature
    - label: Upper critical field at 4.2 K
      benchmark: upper_critical_field
    - label: Melting point (supplier)
      benchmark: melting_point
  handling:
    - Keep it dry, closed and away from oxidising agents, and protect it from electrostatic charge.
    - Use a special powder for metal fires and do not use water on a fire.
    - Limit strain in the wire. Large strain cracks the A15 layer, and that damage is irreversible.
  good_for:
    - High-field magnets at 4 K. ITER's central solenoid is designed for a maximum field of 13 T.
    - 'High critical temperature for a superconductor: 18.3 K is the highest reported for Nb3Sn.'
  watch_out:
    - Brittleness. Large strain cracks the A15 layer irreversibly.
    - Critical current falls off swiftly above about 12 to 15 T for present conductors.
    - Tin deficiency and disorder lower Tc and Hc2 sharply in thin films.
  verdict: Nb3Sn is the superconductor chosen for ITER's highest-field coils and for the HL-LHC quadrupoles. It is brittle and must be kept free of large strain, and the sources read here do not answer its corrosion or oxidation behaviour in air.

References

Every number above carries a reference number. Click one to see the source and where in it the value comes from.

References
Source	Type	Year	Used for
A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State	paper	2006	13 values
Influence of Nb alloying on Nb recrystallization and the upper critical field of Nb3Sn	paper	2024	2 values
American Elements: Niobium tin (CAS 12035-04-0), product page with safety data sheet	datasheet	2026	6 values
ITER Superconducting Magnets (ITER Machine Systems)	web	2026	2 values
CERN gears up for tighter focusing (CERN Courier, 24 March 2025)	web	2025	1 value
Mineral Commodity Summaries 2026, Niobium (Columbium)	report	2026	1 value
Mineral Commodity Summaries 2026, Tin	report	2026	1 value
About the 2025 List of Critical Minerals (USGS, final list of 60 minerals)	web	2025	0 values
Critical raw materials (European Commission, fifth list of 34 critical raw materials)	web	2024	0 values

References
Identity
Formula	Nb3Sn
CAS	12035-04-0
Crystal system	cubic A15 (A3B type, Sn atoms on a bcc sublattice)
Role	A15 superconductor wire for high-field magnets
Benchmarks	14

References
Use this record
YAML CSV JSON CSV has one row per value, with its conditions, method, source and the place in the source.

References
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