Dysprosium Dy

spore: profile
id: dysprosium
spore_version: 0.2
family: rare-earth-metals
name: Dysprosium
abbreviation: Dy
role: permanent-magnet alloying element and neutron absorber
category: metals
type: heavy-metals
summary: |
  Dysprosium is the element Dy (atomic number 66), a silvery heavy rare-earth metal with a density of 8.55 g/cm3 at 25 °C and a melting point of 1412 °C (ESPI). USGS reports magnets as the leading global end use for rare earths as a group, and PubChem lists nuclear control rods among the potential uses of dysprosium. The metal tarnishes in moist air, reacts with water and dilute acids to release hydrogen, and its powder and thin foil are flammable solids. In April 2025 China placed dysprosium under export controls, according to USGS.
best_for: Neutron absorption in nuclear control rods (PubChem lists this as a potential use) and rare-earth magnet alloys (USGS)
weakest_at: Oxidises in moist air and reacts with water and dilute acids to release hydrogen; powder and thin foil are flammable solids (ESPI, PubChem)
identity:
  formula: Dy (element, atomic number 66), a silvery lanthanide metal
  cas: 7429-91-6
  source: pubchem-dy
  where: Names and Identifiers, Other Identifiers, CAS entry (PubChem CID 23912)
tags:
  applications:
    - radiation-shielding
    - mechanisms
properties:
  - benchmark: density
    label: Density, dysprosium metal at 25 °C
    value: 8.55
    unit: g/cm3
    scope: material
    conditions:
      temperature: 25 °C
      unit_in_source: 8.55 g/cc @ 25
      purity: not stated
    method: Specific gravity printed in a supplier safety data sheet (ESPI, revised May 2011)
    status: ground
    source: espi-dy-sds
    where: Section III, Physical Data, Specific Gravity
  - benchmark: density
    label: Density, dysprosium at 25 °C (PubChem)
    value: 8.54
    unit: g/cm3
    scope: material
    conditions:
      temperature: 25 °C
      unit_in_source: 8.54 @25 °C
    method: Experimental density printed in the PubChem record
    status: ground
    note: The SDS gives 8.55 and PubChem 8.54 at the same temperature. Both are recorded.
    source: pubchem-dy
    where: Chemical and Physical Properties, Experimental Properties, Density
  - benchmark: melting_point
    label: Melting point, dysprosium (ESPI)
    value: 1412
    unit: °C
    scope: material
    conditions:
      pressure: not stated
      unit_in_source: 1412 oC
    method: Value printed in a supplier safety data sheet
    status: ground
    source: espi-dy-sds
    where: Section III, Physical Data, Melting Point
  - benchmark: melting_point
    label: Melting point, dysprosium (PubChem)
    value: 1409
    unit: °C
    scope: material
    conditions:
      pressure: not stated
      unit_in_source: 1409 °C
    method: Experimental melting point printed in the PubChem record
    status: ground
    note: ESPI prints 1412 °C and PubChem 1409 °C, a difference of 3 °C. Both are recorded.
    source: pubchem-dy
    where: Chemical and Physical Properties, Experimental Properties, Melting Point
  - benchmark: boiling_point
    label: Boiling point, dysprosium (ESPI)
    value: 2562
    unit: °C
    scope: material
    conditions:
      pressure: not stated
      unit_in_source: 2562 oC
    method: Value printed in a supplier safety data sheet
    status: ground
    note: PubChem gives 2335 °C at 760 mmHg, about 227 °C lower. The two sources are not reconciled, and both are recorded.
    source: espi-dy-sds
    where: Section III, Physical Data, Boiling Point
  - benchmark: boiling_point
    label: Boiling point, dysprosium at 760 mmHg (PubChem)
    value: 2335
    unit: °C
    scope: material
    conditions:
      pressure: 760 mmHg
      unit_in_source: 2335 °C @760 [mm Hg]
    method: Experimental boiling point printed in the PubChem record
    status: ground
    source: pubchem-dy
    where: Chemical and Physical Properties, Experimental Properties, Boiling Point
  - benchmark: thermal_conductivity
    label: Thermal conductivity, dysprosium
    value: 11
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: not stated
      unit_in_source: 11 W m-1 K-1
    method: Value printed on the WebElements physical properties page
    status: ground
    source: webelements-dy-physics
    where: Heat and conduction, Thermal conductivity
  - benchmark: cte
    label: Coefficient of linear thermal expansion, dysprosium
    value: 9.9
    unit: ppm/K
    scope: material
    conditions:
      temperature: not stated
      unit_in_source: 9.9 × 10-6 K-1
    method: Value printed on the WebElements physical properties page; 10-6 K-1 is the same unit as ppm/K
    status: ground
    source: webelements-dy-physics
    where: Heat and conduction, Coefficient of linear thermal expansion
  - benchmark: elastic_modulus
    label: Young's modulus, dysprosium
    value: 61
    unit: GPa
    scope: material
    conditions:
      temperature: not stated
      unit_in_source: 61 GPa
    method: Value printed on the WebElements physical properties page
    status: ground
    source: webelements-dy-physics
    where: Elastic properties, Young's modulus
  - benchmark: shear_modulus
    label: Rigidity (shear) modulus, dysprosium
    value: 25
    unit: GPa
    scope: material
    conditions:
      temperature: not stated
      unit_in_source: 25 GPa
    method: Value printed as rigidity modulus on the WebElements physical properties page; rigidity modulus is the shear modulus
    status: ground
    source: webelements-dy-physics
    where: Elastic properties, Rigidity modulus
  - benchmark: bulk_modulus
    label: Bulk modulus, dysprosium
    value: 41
    unit: GPa
    scope: material
    conditions:
      temperature: not stated
      unit_in_source: 41 GPa
    method: Value printed on the WebElements physical properties page
    status: ground
    source: webelements-dy-physics
    where: Elastic properties, Bulk modulus
  - benchmark: poissons_ratio
    label: Poisson's ratio, dysprosium
    value: 0.25
    unit: '-'
    scope: material
    conditions:
      temperature: not stated
    method: Value printed on the WebElements physical properties page
    status: ground
    source: webelements-dy-physics
    where: Elastic properties, Poisson's ratio
  - benchmark: vickers_hardness
    label: Vickers hardness, dysprosium
    value: 540
    unit: MPa
    scope: material
    conditions:
      temperature: not stated
      unit_in_source: 540 MN m-2
    method: Value printed as MN m-2 on the WebElements physical properties page; 1 MN/m2 equals 1 MPa
    status: ground
    note: vickers_hardness is not a canonical name in the property file, so it is listed in gaps as a new name.
    source: webelements-dy-physics
    where: Hardnesses, Vickers hardness
corrosion:
  - environment: Moist air at room temperature
    headline: Dysprosium tarnishes slowly in moist air, and its crystals oxidise in moist air.
    effect: PubChem describes the metal as crystals that oxidise in moist air and as stable in air at room temperature. WebElements says the metal tarnishes slowly in air. Dry air is not described as a problem in the sources read.
    rating: moderate
    conditions:
      temperature: room temperature
      atmosphere: moist air
    source: pubchem-dy
    where: Chemical and Physical Properties, Experimental Properties, Physical Description
  - environment: Air, when heated
    headline: Dysprosium burns readily in air to form the oxide Dy2O3.
    effect: WebElements states that the metal tarnishes slowly in air and burns readily to form dysprosium(III) oxide, Dy2O3, with the equation 4Dy + 3O2 gives 2Dy2O3. The source does not give an ignition temperature.
    rating: severe
    conditions:
      temperature: heated, temperature not stated
      product: Dy2O3
    source: webelements-dy-chem
    where: Reaction of dysprosium with air
  - environment: Cold and hot water
    headline: Water is attacked slowly when cold and quickly when hot, releasing hydrogen.
    effect: WebElements says the metal is quite electropositive, reacts slowly with cold water and quite quickly with hot water to form dysprosium hydroxide, Dy(OH)3, and hydrogen gas. ESPI says the metal may react with water to release flammable, explosive hydrogen gas.
    rating: severe
    conditions:
      temperature: cold and hot water
    source: webelements-dy-chem
    where: Reaction of dysprosium with water
  - environment: Dilute acids and halogens
    headline: Dilute acids dissolve the metal readily, and all halogens react with it.
    effect: WebElements says the metal dissolves readily in dilute sulphuric acid with release of hydrogen, and reacts with all halogens to form the trihalides. ESPI states that all forms react with dilute acids, emitting flammable and explosive hydrogen gas, and lists strong acids and halogens as incompatible.
    rating: severe
    conditions:
      acid: dilute sulphuric acid
      halogens: fluorine, chlorine, bromine, iodine
    source: webelements-dy-chem
    where: Reaction of dysprosium with acids; Reaction of dysprosium with the halogens
  - environment: Thin foil in air at elevated temperature and in moisture
    headline: Thin foil oxidises at elevated temperature and deteriorates in moisture, and pinholes form as it ages.
    effect: ESPI states that foils are subject to oxidation at elevated temperatures, deteriorate in the presence of moisture, fingerprint easily, and may develop pinholes as the metal ages. The sheet gives no rate or temperature.
    rating: moderate
    conditions:
      form: thin foil
      temperature: elevated, not stated
    source: espi-dy-sds
    where: Section IX, Special Precautions, Other Precautions
risks:
  hazards:
    - text: 'PubChem GHS summary, ECHA C&L notifications: H228 (60%) flammable solid, H250 (16.2%) catches fire spontaneously if exposed to air, H251 (21%) and H252 (16.2%) self-heating, H260 (16.2%) releases flammable gases in contact with water, H315 (21%) skin irritation, H319 (21%) serious eye irritation, H413 (21%) long-lasting harm to aquatic life. Signal word Danger. Of 105 company reports, 25 (23.8%) say the substance does not meet GHS criteria, so classification depends on the form and notifier.'
      ghs:
        - H228
        - H250
        - H251
        - H252
        - H260
        - H315
        - H319
        - H413
      source: pubchem-dy
      where: Safety and Hazards, Hazards Identification, GHS Classification
    - text: 'ESPI safety data sheet (revised May 2011): powder hazard rating HMIS health 2, flammability 3, reactivity 2. Warning statement: flammable solid when in a powder or thin foil. The sheet says the metal is considered a rare-earth metal and that such metals are moderately to highly toxic, but adds that the properties of dysprosium have not been thoroughly investigated.'
      ghs: []
      source: espi-dy-sds
      where: Section II, Hazardous Ingredients; Section IV, Fire and Explosion Hazards; Section V, Health Hazard Information; Section IX, Warning Statements
  failure_risks:
    - mode: Fire in powder and thin foil
      trigger: Powder or thin foil exposed to a spark, static electricity or air. PubChem reports spontaneous ignition in air for the H250 notifications.
      consequence: ESPI says the metal will burn under fire conditions, thin foils may ignite from a spark or static charge, and powder mixed with air in critical proportions can explode when an ignition source is present.
      severity: critical
      source: espi-dy-sds
      where: Section IV, Fire and Explosion Hazards; Section IX, Other Precautions
    - mode: Hydrogen release on contact with water or acid
      trigger: Contact with cold or hot water, or with dilute acids
      consequence: The metal releases flammable, explosive hydrogen gas (ESPI). WebElements gives the reaction with hot water and dilute sulphuric acid. PubChem lists H260 for the same hazard.
      severity: critical
      source: espi-dy-sds
      where: Section IV, Unusual Fire and Explosion Hazard; Section IX, Warning Statements
    - mode: Oxidation and pinholes in thin foil
      trigger: Thin foil held at elevated temperature or in moisture, or over long storage
      consequence: ESPI says foils oxidise at elevated temperatures, deteriorate in moisture, and may develop pinholes as the metal ages. The sheet gives no time or temperature limit.
      severity: moderate
      source: espi-dy-sds
      where: Section IX, Special Precautions, Other Precautions
  side_effects:
    - text: The metal fingerprints easily, and ESPI says foils also tarnish with age. Both affect the surface of foil and plate before use.
      affects: Surface finish of foil and sputtering targets
      source: espi-dy-sds
      where: Section IX, Other Precautions
  handling:
    - text: Store under argon or another inert gas, in a cool dry place in tightly closed containers, away from oxidisers, halogens, acids and moisture (ESPI).
      source: espi-dy-sds
      where: Section VIII, Ventilation; Section IX, Precautions to Be Taken in Handling and Storage
    - text: Use dry powder or a Class D extinguisher on fires. Do not use water (ESPI). Firefighters need self-contained breathing apparatus.
      source: espi-dy-sds
      where: Section IV, Extinguishing Media and Special Firefighting Procedures
    - text: Use non-sparking tools and grounded or bonded equipment when transferring the material, and avoid creating dust. Use a NIOSH-approved respirator in dusting conditions (ESPI).
      source: espi-dy-sds
      where: Section VIII, Respiratory Protection; Section IX, Other Precautions
    - text: The transport classification differs by form. Solid forms have no DOT hazard class in the sheet, thin foil is UN3178 class 4.1, and powder is UN3089 class 4.1 (ESPI).
      source: espi-dy-sds
      where: DOT Regulations
  mitigations: []
uses:
  - application: radiation-shielding
    device: Nuclear reactor control rods (potential use)
    example: PubChem lists the potential uses of dysprosium as nuclear control rods, stainless steel alloys, laser materials and research, and says it is used to measure neutron flux.
    source: pubchem-dy
    where: Use and Manufacturing, Uses, Sources/Uses
  - application: mechanisms
    device: Neodymium-iron-boron permanent magnets for motors and generators
    example: USGS reports that magnets were the estimated leading global end use of rare earths in 2025, and that heavy rare earths were used in high-strength magnets.
    source: usgs-mcs2026-rare-earths
    where: Domestic Production and Use paragraph; heavy-rare-earth use in the Rare Earths (Heavy) chapter, Domestic Production and Use paragraph
supply:
  - subject: Rare earths, all (REO equivalent; dysprosium is not reported separately)
    producers:
      - country: China
        share_percent: 69.2
        year: 2025
      - country: United States
        share_percent: 13.1
        year: 2025
      - country: Australia
        share_percent: 7.4
        year: 2025
      - country: Burma
        share_percent: 5.6
        year: 2025
    critical_lists: []
    recycling: 'USGS: limited quantities of rare earths were recovered from batteries, permanent magnets and fluorescent lamps. The heavy-rare-earth chapter says small quantities of heavy rare earths were recovered from permanent magnets.'
    substitutes:
      - 'USGS: light rare earths can substitute for heavy rare earths in several applications, but substitutes are generally less effective.'
    source: usgs-mcs2026-rare-earths
    where: 'World Mine Production and Reserves table, 2025 (world total 390,000 t REO, rounded). Shares calculated by Space Mushroom from the printed tonnes: China 270,000, United States 51,000, Australia 29,000, Burma 22,000. USGS prints no dysprosium-only production figure.'
  - subject: Heavy rare earths, including dysprosium (import data)
    producers: []
    critical_lists:
      - list: EU critical raw materials list (heavy rare earth elements group, as shown on the European Commission page)
        listed: true
    recycling: 'USGS: small quantities of heavy rare earths were recovered from permanent magnets.'
    substitutes:
      - 'USGS: light rare earths can substitute for heavy rare earths in several applications.'
    source: usgs-mcs2026-rare-earths-heavy
    where: 'Salient Statistics: U.S. imports of heavy rare-earth compounds and metals, 71 t (2021), 70 t, 70 t, 74 t and 100 t (2025e). Import Sources paragraph gives China as the source for terbium, holmium and lutetium, but not for dysprosium. Dysprosium oxide 99.5% minimum price: 410 USD/kg (2021) and 239 USD/kg (2025e).'
    export_controls: 'USGS: in April 2025 China added controls on metals, oxides, alloys and compounds of dysprosium. In November 2025 it suspended its later October controls for one year, while the April controls remained in effect.'
documents:
  - title: 'ESPI Metals material safety data sheet: Dysprosium (CAS 7429-91-6), copy hosted by Purdue PRIME Lab, revised May 2011'
    type: sds
    url: https://www.physics.purdue.edu/primelab/safety/MSDS/Retired%20SDS%20and%20MSDS/2017%20removed%20safety%20sheets/MSDS%20updated%20to%20SDS/dysprosium%20metal%20%20-%20ESPI.pdf
    year: 2012
  - title: 'PubChem compound record: Dysprosium (CID 23912), with ECHA C&L Inventory classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23912
    year: 2026
  - title: 'WebElements: Dysprosium, physical properties'
    type: database
    url: https://www.webelements.com/dysprosium/physics.html
    year: 2026
  - title: 'WebElements: Dysprosium, reactions of elements'
    type: database
    url: https://www.webelements.com/dysprosium/chemistry.html
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Rare Earths'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Rare Earths (Heavy)'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths-heavy.pdf
    year: 2026
  - title: 'European Commission: Critical raw materials'
    type: database
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    year: 2024
  - title: 'Wikipedia: Dysprosium (used for production route and history only)'
    type: database
    url: https://en.wikipedia.org/wiki/Dysprosium
    year: 2026
gaps:
  - No space flight, vacuum, radiation or thermal-vacuum result for dysprosium metal was found in the sources read. The adiabatic demagnetisation refrigerator magnet paper (Milward et al., XEUS, IEEE 2005) was not reachable in this run, so no space use is entered.
  - Specific heat capacity, Curie temperature (90.5 K) and the paramagnetic transition (179 K) are printed in Wikipedia only. They were not entered because the source rule limits Wikipedia to composition and history, and no other fetched source gave them.
  - 'Thermal neutron cross-section: no fetched source printed the value for natural dysprosium, so thermal_neutron_cross_section is not entered.'
  - 'Electrical resistivity: WebElements prints 92.6 × 10-8 Ω m. The exponent format did not match the verification check, so the value was left out.'
  - 'Tensile and yield strength of dysprosium metal: no value from a fetched source. ESPI and WebElements give hardness only.'
  - 'Crustal abundance of dysprosium: Wikipedia prints 5.2 mg/kg only, so it is not entered under the source rule. The WebElements abundance figure is a graphic and could not be read.'
  - 'Dysprosium-only production: USGS reports rare earths as a group, so the supply shares are for all rare earths and are calculated from the printed tonnes.'
  - 'US critical-mineral listing: the USGS 2025 critical-minerals page returned HTTP 403, so critical_lists records only the EU heavy rare earth elements group.'
  - 'Boiling point: ESPI gives 2562 °C and PubChem gives 2335 °C at 760 mmHg. The difference of about 227 °C is not reconciled, and both are recorded.'
  - 'Melting point: ESPI gives 1412 °C and PubChem gives 1409 °C. Both are recorded.'
  - 'Process steps: the reduction of DyF3 or DyCl3 with calcium or lithium is described in Wikipedia only and is recorded in the recipe line as composition and production context, not as a measured value.'
  - Hazard data rest on one supplier SDS (2011 revision) and the PubChem summary. The ChemicalBook SDS was not opened, and no current major-supplier SDS for pure dysprosium metal was fetched. The ESPI SDS is dated, so the hazard entries need a current sheet.
  - The Goodfellow dysprosium page was read but not used for values. Its text contains statements that could not be traced to a cited source, such as an unattributed neutron cross-section for the 164Dy isotope and an unattributed tensile strength.
  - Dysprosium-specific use in NdFeB magnets (for example the 6% neodymium substitution figure in Wikipedia) was not entered. The magnet use is supported only by USGS statements about rare earths as a group.
  - vickers_hardness is a new name because the property file has no canonical name for hardness. It is listed here for review.
sources:
  espi-dy-sds:
    title: 'Material Safety Data Sheet: Dysprosium (ESPI Metals, revised May 2011), copy hosted by Purdue PRIME Lab'
    id: CAS 7429-91-6
    url: https://www.physics.purdue.edu/primelab/safety/MSDS/Retired%20SDS%20and%20MSDS/2017%20removed%20safety%20sheets/MSDS%20updated%20to%20SDS/dysprosium%20metal%20%20-%20ESPI.pdf
    year: 2012
    kind: datasheet
    license: supplier safety data sheet, cited not reproduced
  pubchem-dy:
    title: 'PubChem compound record: Dysprosium (CID 23912), including ECHA C&L Inventory classification'
    id: CID 23912; CAS 7429-91-6
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23912/JSON
    year: 2026
    kind: database
    license: public domain (NCBI); sections attributed to ECHA and others
  webelements-dy-physics:
    title: 'WebElements: Dysprosium, physical properties (Mark Winter, University of Sheffield)'
    url: https://www.webelements.com/dysprosium/physics.html
    year: 2026
    kind: web
    license: WebElements, copyright 1993-2026 Mark Winter, cited not reproduced
  webelements-dy-chem:
    title: 'WebElements: Dysprosium, reactions of elements (Mark Winter, University of Sheffield)'
    url: https://www.webelements.com/dysprosium/chemistry.html
    year: 2026
    kind: web
    license: WebElements, copyright 1993-2026 Mark Winter, cited not reproduced
  usgs-mcs2026-rare-earths:
    title: 'Mineral Commodity Summaries 2026: Rare Earths (USGS)'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-rare-earths-heavy:
    title: 'Mineral Commodity Summaries 2026: Rare Earths (Heavy) (USGS)'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths-heavy.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  ec-crm:
    title: Critical raw materials (European Commission, list of 34 critical raw materials under Regulation (EU) 2024/1252)
    id: Regulation (EU) 2024/1252
    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
  wikipedia-dy:
    title: Dysprosium (Wikipedia)
    url: https://en.wikipedia.org/wiki/Dysprosium
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 13
  unreachable: 2
  caveats: 5
  note: 'Values were read by an AI assistant on 2026-10-26 from the pages and PDFs named in each entry. Unreachable: USGS 2025 critical-minerals page (HTTP 403); the Milward et al. space-magnet paper (not reachable in this run). Caveats: the boiling point differs by about 227 °C between ESPI and PubChem; the melting point differs by 3 °C; the hazard sources are a 2011 supplier SDS and PubChem; supply shares are rare-earth group shares, calculated from USGS tonnes, not dysprosium-only figures.'
story:
  risk_groups:
    - title: For people
      lead: The hazard is in the fine form. Solid metal is less of a concern than powder or thin foil, which are flammable solids, and the sources disagree on the classification.
      level: 1
      verdict: Form-dependent
      points:
        - label: Powder and thin foil
          line: PubChem lists H228, flammable solid, for 60% of notifications and H250, catches fire spontaneously in air, for 16.2%. ESPI says the metal is a flammable solid when in powder or thin foil form.
        - label: Skin and eyes
          line: PubChem lists H315 skin irritation and H319 serious eye irritation for 21% of notifications. ESPI says to wash exposed skin and flush eyes.
        - label: Dust
          line: ESPI says dust may explode when mixed with air in the presence of an ignition source, and recommends a NIOSH-approved respirator where dust forms.
    - title: If it fails
      lead: 'The sources give three failure routes: a fire in powder or foil, hydrogen release on contact with water or acid, and oxidation of thin foil.'
      points:
        - label: Fire
          line: ESPI says the metal burns under fire conditions, and thin foil can be ignited by a spark or static charge. Use dry powder or a Class D extinguisher, and do not use water.
        - label: Water and acid
          line: WebElements says the metal reacts slowly with cold water and quickly with hot water to release hydrogen, and that it dissolves in dilute sulphuric acid. ESPI says all forms react with dilute acids, releasing flammable and explosive hydrogen.
        - label: Air and moisture
          line: PubChem says the crystals oxidise in moist air. ESPI says thin foils oxidise at elevated temperature, deteriorate in moisture and may develop pinholes with age.
    - title: Handling and storage
      points:
        - label: Store under inert gas
          line: ESPI says to store the metal under argon or another inert gas, in a cool dry place, in tightly closed containers, away from oxidisers, halogens and acids.
        - label: Transport
          line: ESPI lists thin foil as UN3178 and powder as UN3089, both class 4.1 flammable solids, and the solid form with no DOT hazard class.
  why: 'Dysprosium is a heavy rare-earth metal. PubChem says it is used primarily in the form of various salts. The sources read here point to two uses: nuclear control rods, which PubChem lists as a potential use, and permanent magnets, where USGS reports magnets as the leading global end use of rare earths as a group. Its reactions with air, water and acid make the metal a fire hazard in fine form. In April 2025 China placed dysprosium under export controls, which USGS says affects the supply of this element.'
  uses:
    - where: Nuclear control rods (potential use)
      line: PubChem lists nuclear control rods among the potential uses of dysprosium, alongside stainless steel alloys and laser materials.
    - where: Permanent magnets
      line: USGS reports that magnets were the estimated leading global end use of rare earths in 2025, and that heavy rare earths are used in high-strength magnets.
  can_do:
    - label: Melting
      value: 1412 °C
      benchmark: melting_point
      line: The melting point is 1412 °C in ESPI's sheet and 1409 °C in PubChem. PubChem gives a boiling point of 2335 °C at 760 mmHg.
    - label: Density
      value: 8.55 g/cm3
      benchmark: density
      line: The density at 25 °C is 8.55 g/cm3 in ESPI's sheet and 8.54 g/cm3 in PubChem.
    - label: Stiffness
      value: 61 GPa
      benchmark: elastic_modulus
      line: Young's modulus is 61 GPa, with a rigidity modulus of 25 GPa, a bulk modulus of 41 GPa and a Poisson's ratio of 0.25 (WebElements).
    - label: Heat conduction
      value: 11 W/(m·K)
      benchmark: thermal_conductivity
      line: Thermal conductivity is 11 W/(m·K), and the coefficient of linear thermal expansion is 9.9 ppm/K (WebElements).
    - label: Hardness
      value: 540 MPa
      line: Vickers hardness is 540 MPa (WebElements, printed as MN m-2). The metal is soft compared with most structural metals.
  compare: Dysprosium's values are read here on their own. Its thermal conductivity of 11 W/(m·K) is low for a metal, and it is soft, with a Vickers hardness of 540 MPa. The sources read here give no rare-earth comparison table, so no other element is compared numerically in this profile.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  recipe:
    line: Dysprosium is a single-element metal (Dy, atomic number 66). It is made by reducing dysprosium fluoride or chloride with calcium or lithium, after the ion-exchange separation from other rare earths (Wikipedia, production section). ESPI and WebElements describe the metal in its pure elemental form.
    parts:
      - name: Dysprosium
        symbol: Dy
        atoms: 1
        atomic_weight: 162.5
        role: The whole material. Pure dysprosium is a single element with no alloying addition in the sources read here. PubChem gives the atomic weight for the element.
  handling:
    - Store under argon or another inert gas, in a cool dry place, in tightly closed containers (ESPI).
    - Use dry powder or a Class D extinguisher on fires. Do not use water (ESPI).
    - Use non-sparking tools and avoid creating dust. Wear a NIOSH-approved respirator where dust forms (ESPI).
  good_for:
    - 'Permanent magnet alloys: dysprosium is a rare-earth addition in the magnet sector, where USGS reports magnets as the leading global end use of rare earths as a group.'
    - 'Nuclear control rods: PubChem lists this as a potential use.'
  watch_out:
    - Powder and thin foil are flammable solids, and water on the metal releases hydrogen (ESPI, PubChem).
    - The sources disagree on boiling point (2562 °C against 2335 °C) and on hazard classification (60% of PubChem notifications are flammable solid, 23.8% say the substance does not meet GHS criteria).
    - 'Supply is concentrated: China is the largest rare-earth producer at 69.2% of the 2025 total, and China placed dysprosium under export controls in April 2025 (USGS).'
  verdict: Dysprosium is a silvery heavy rare-earth metal with a density of 8.55 g/cm3 and a melting point of 1412 °C. Its uses in magnets and control rods are supported by the sources read here, but its supply data are for the rare-earth group rather than for dysprosium alone. The fine metal is a fire hazard, and the metal reacts with air, water and acid, so it needs inert, dry handling. No space application was found in the sources read.