Praseodymium Pr

spore: profile
id: praseodymium
spore_version: 0.2
family: rare-earth-metals
name: Praseodymium
abbreviation: Pr
role: magnet and optical rare-earth metal
category: metals
type: heavy-metals
summary: |
  Praseodymium is the element Pr (atomic number 59), the third lanthanide. It is a soft, silvery, ductile metal with a density of 6.773 g/cm3 at 20 °C and a melting point of 931 °C. It never occurs alone and is extracted with neodymium from bastnaesite and monazite ores. Its main modern use is in neodymium-praseodymium permanent magnets, and its Pr3+ ions are used as dopants in lasers and fibre amplifiers. The metal tarnishes in air, and the supplier safety sheets disagree on whether fine powder is pyrophoric.
best_for: High-power NdPr permanent magnets, and Pr3+ optical dopants in lasers and fibre amplifiers (Wikipedia; USGS)
weakest_at: 'Handling: the metal tarnishes in air, reacts with water, and fine powder is classed as pyrophoric (H250) in two supplier sheets (Wikipedia; Apollo Scientific; Stanford Advanced Materials)'
identity:
  formula: Pr (element, atomic number 59); its one stable isotope is Pr-141 (Wikipedia)
  cas: 7440-10-0
  source: pubchem-pr
  where: Other Identifiers, CAS entry (PubChem CID 23942)
tags:
  applications:
    - mechanisms
    - optics-and-cameras
    - structures
properties:
  - benchmark: density
    label: Density, praseodymium at 20 °C
    value: 6.773
    unit: g/cm3
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: 6.773 g/cm3 (at 20 °C)
    method: Value printed in the Wikipedia element infobox, which cites Arblaster 2018 (Selected Values of the Crystallographic Properties of Elements)
    status: ground
    source: wikipedia-pr
    where: Infobox, Density row (at 20 °C)
  - benchmark: density
    label: Density, praseodymium at 25 °C (supplier SDS)
    value: 6.71
    unit: g/cm3
    scope: material
    conditions:
      temperature: 25 °C
      unit_in_source: 6.71 g/cm3 at 25 °C (77 °F)
    method: Relative density printed in section 9 of a supplier safety data sheet
    status: ground
    note: The Wikipedia and Ames sheets give 6.773 g/cm3, so the sources differ by about 1 %. Both values are recorded.
    source: sam-pr-sds
    where: Section 9, property m) Relative density
  - benchmark: melting_point
    label: Melting point, praseodymium
    value: 931
    unit: °C
    scope: material
    conditions:
      unit_in_source: 1204 K (931 °C, 1708 °F)
      pressure: not stated
    method: Value printed in the Wikipedia element infobox (cited there to Arblaster 2018)
    status: ground
    note: The ACI and Stanford sheets also print 931 °C, the Ames sheet prints 935 °C, and Theodore Gray's table prints 930.85 °C (not entered as a source).
    source: wikipedia-pr
    where: Infobox, Melting point row
  - benchmark: boiling_point
    label: Boiling point, praseodymium
    value: 3512
    unit: °C
    scope: material
    conditions:
      pressure: 760 mmHg
      unit_in_source: 3512 °C @760 [mm Hg]
    method: Experimental property printed in the PubChem record; the ACI sheet prints the same 3512 °C
    status: ground
    note: The Wikipedia infobox gives 3130 °C (3403 K) and the Ames and Stanford sheets give 3520 °C, so the sources differ by up to 390 °C. The PubChem value is entered and the difference is not reconciled.
    source: pubchem-pr
    where: Chemical and Physical Properties, Experimental Properties, Boiling Point
  - benchmark: thermal_conductivity
    label: Thermal conductivity, praseodymium
    value: 12.5
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: not stated in the infobox
      unit_in_source: 12.5 W/(m·K)
    method: Value printed in the Wikipedia element infobox; no temperature is given there
    status: ground
    note: Only one source gave this value. American Elements (HTTP 403) was not opened.
    source: wikipedia-pr
    where: Infobox, Thermal conductivity row
  - benchmark: specific_heat
    label: Specific heat capacity, praseodymium
    value: 193.031
    unit: J/(kg·K)
    scope: material
    conditions:
      temperature: not stated in the infobox
      unit_in_source: 193.031 J/(kg·K)
    method: Value printed in the Wikipedia element infobox; the molar value, 27.20 J/(mol·K), sits in the same table
    status: ground
    source: wikipedia-pr
    where: Infobox, Specific heat capacity row
  - benchmark: cte
    label: Coefficient of thermal expansion, praseodymium at 20 °C
    value: 4.5
    unit: ppm/K
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: 4.5 × 10 −6 /K (at 20 °C)
    method: Value printed in the Wikipedia infobox. 10 to the power -6 per K is the same unit as ppm/K. The Wikipedia note says expansion is strongly anisotropic between crystal axes, so one figure is a simplification.
    status: ground
    source: wikipedia-pr
    where: Infobox, Thermal expansion row
  - benchmark: elastic_modulus
    label: Young's modulus, praseodymium
    value: 37.3
    unit: GPa
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia element infobox
    status: ground
    source: wikipedia-pr
    where: Infobox, Young's modulus row
  - benchmark: shear_modulus
    label: Shear modulus, praseodymium
    value: 14.8
    unit: GPa
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia element infobox
    status: ground
    source: wikipedia-pr
    where: Infobox, Shear modulus row
  - benchmark: bulk_modulus
    label: Bulk modulus, praseodymium
    value: 28.8
    unit: GPa
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia element infobox
    status: ground
    source: wikipedia-pr
    where: Infobox, Bulk modulus row
  - benchmark: poissons_ratio
    label: Poisson's ratio, praseodymium
    value: 0.281
    unit: '-'
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia element infobox
    status: ground
    source: wikipedia-pr
    where: Infobox, Poisson ratio row
  - benchmark: vickers_hardness
    label: Vickers hardness, praseodymium
    value: 250
    value_high: 745
    unit: MPa
    scope: material
    conditions:
      temperature: not stated in the infobox
      unit_in_source: 250–745 MPa
    method: Range printed in the Wikipedia element infobox; the load used for the test is not stated
    status: ground
    note: No canonical name exists for hardness in the property file, so vickers_hardness is a new name and is listed in gaps.
    source: wikipedia-pr
    where: Infobox, Vickers hardness row
  - benchmark: brinell_hardness
    label: Brinell hardness, praseodymium
    value: 250
    value_high: 640
    unit: MPa
    scope: material
    conditions:
      temperature: not stated in the infobox
      unit_in_source: 250–640 MPa
    method: Range printed in the Wikipedia element infobox; the ball and load are not stated
    status: ground
    note: No canonical name exists for hardness in the property file, so brinell_hardness is a new name and is listed in gaps.
    source: wikipedia-pr
    where: Infobox, Brinell hardness row
  - benchmark: electrical_resistivity
    label: Electrical resistivity, polycrystalline praseodymium at room temperature
    value: 0.7
    unit: µΩ·m
    scope: material
    conditions:
      temperature: room temperature
      form: polycrystalline (infobox label 'poly')
      unit_in_source: 0.700 µΩ·m (at room temperature)
    method: Value printed in the Wikipedia element infobox; the unit is converted to the canonical Ω·m on import
    status: ground
    source: wikipedia-pr
    where: Infobox, Electrical resistivity row
corrosion:
  - environment: Air at room temperature
    headline: Praseodymium tarnishes in air and forms a flaking green oxide, and a centimetre-sized sample corrodes completely in about a year.
    effect: Wikipedia says the metal tarnishes slowly in air, forming a spalling green oxide layer like iron rust. It cites a long-term air exposure test for the one-year figure for a centimetre-sized sample. No humidity or time basis is given for the test.
    rating: moderate
    conditions:
      atmosphere: air
      temperature: room temperature
    source: wikipedia-pr
    where: Reactions with air, first paragraph
  - environment: Air and moisture during storage
    headline: The ACI Alloys sheet for a 99.9 % ingot says the metal is air sensitive and moisture sensitive.
    effect: The ACI sheet says the material is moisture sensitive and air sensitive, that it develops a green coating on air exposure, and that conditions to avoid include moisture and exposure to air. It recommends storing under argon and protecting it from moisture.
    rating: moderate
    conditions:
      form: 99.9 % ingot
      storage: under argon
    source: aci-pr-sds
    where: Section 10 Stability and Reactivity; Section 7 Handling and Storage
  - environment: Hot and cold water
    headline: Praseodymium reacts slowly with cold water and quite quickly with hot water to form the hydroxide.
    effect: Wikipedia says praseodymium is electropositive and reacts slowly with cold water and quite quickly with hot water to form praseodymium(III) hydroxide. The Ames sheet says it decomposes in water.
    rating: severe
    conditions:
      temperature: cold and hot water, not quantified
    source: wikipedia-pr
    where: Reactions with water paragraph
  - environment: Water in a fire
    headline: The Stanford sheet says the metal reacts violently with water, so water is limited to cooling unopened containers.
    effect: The Stanford Advanced Materials sheet says the substance reacts violently with water, and recommends water spray only to cool unopened containers. It gives dry sand, dry chemical or alcohol-resistant foam for a fire.
    rating: severe
    conditions:
      form: metal (form not given)
    source: sam-pr-sds
    where: Section 10.3 Possibility of hazardous reactions; Section 5 Firefighting measures
  - environment: Dilute sulfuric acid
    headline: Praseodymium dissolves readily in dilute sulfuric acid to give the Pr3+ ion.
    effect: Wikipedia says praseodymium dissolves readily in dilute sulfuric acid, giving chartreuse Pr3+ ions that exist as nine-water complexes. The Pr3+/Pr couple is at -2.35 V.
    rating: moderate
    conditions:
      acid: dilute sulfuric acid
      temperature: not stated
    source: wikipedia-pr
    where: Aqueous chemistry, paragraph on sulfuric acid
  - environment: Heating in air
    headline: Praseodymium burns readily at 150 °C to form a mixed oxide close to Pr6O11.
    effect: Wikipedia says the metal burns readily at 150 °C to form praseodymium(III,IV) oxide, approximately Pr6O11. The ACI sheet says irritating and toxic fumes form on combustion.
    rating: severe
    conditions:
      temperature: 150 °C
      atmosphere: air
    source: wikipedia-pr
    where: Reactions with oxygen paragraph
risks:
  hazards:
    - text: 'PubChem reports the ECHA C&L notifications for 247 company reports: H228 flammable solid (52.6 %), H250 catches fire spontaneously if exposed to air (28.3 %), H251 self-heating (52.6 %), H315 skin irritation (53.8 %), H319 serious eye irritation (53.8 %), H413 long-lasting aquatic harm (10.9 %). Signal word Danger. 18.2 % of reports say the substance does not meet GHS criteria.'
      ghs:
        - H228
        - H250
        - H251
        - H315
        - H319
        - H413
      source: pubchem-pr
      where: Safety and Hazards, Hazards Identification, GHS Classification
    - text: 'Wikipedia''s infobox cites a Sigma-Aldrich listing for hazard data: GHS02 flame pictogram, signal word Danger, and H250. The Sigma-Aldrich sheet itself was not opened.'
      ghs:
        - H250
      source: wikipedia-pr
      where: Chembox Hazards section, GHS pictograms and H-phrases
    - text: 'Stanford Advanced Materials sheet for praseodymium metal: pyrophoric solids category 1, H250 catches fire spontaneously if exposed to air. Precautionary P231 handle under inert gas and P422 store under inert gas. Transport UN 3208, class 4.3, packing group I (metallic substance, water-reactive).'
      ghs:
        - H250
      source: sam-pr-sds
      where: Section 2.1 Classification, Section 2.2 Labelling; Section 14 Transport
    - text: 'Apollo Scientific sheet for praseodymium powder, -40 mesh: H250 pyrophoric solids, category 1, with classification drawn from EU Regulation 1272/2008 Annex VI.'
      ghs:
        - H250
      source: apollo-pr-sds
      where: Section 2.1 Classification of the substance or mixture
    - text: 'Ames Laboratory sheet for pieces, ingot, rod, foil, sheet and target (revised 2016-01-26): not classified as hazardous under 29 CFR 1910.1200, with hazard statements N/A. Under normal handling, solid forms present few health hazards; grinding, melting or welding may create dust or fumes.'
      ghs: []
      source: purdue-pr-sds
      where: Section 2 Hazards Identification
    - text: 'ACI Alloys sheet for 99.9 % ingot: hazard symbols and risk phrases listed as none. May cause eye, skin and respiratory irritation. Toxicological properties have not been fully investigated.'
      ghs: []
      source: aci-pr-sds
      where: Section 2 Hazards Identification; Section 3 Composition
  failure_risks:
    - mode: Ignition of fine powder or chips in air
      trigger: Powder, chips or turnings exposed to air
      consequence: The 40-mesh powder is classed as pyrophoric (H250, Apollo Scientific), and the Stanford sheet classes the metal as pyrophoric category 1, so fines can catch fire without an external heat source.
      severity: critical
      source: apollo-pr-sds
      where: Section 2.1 Classification
    - mode: Violent reaction with water
      trigger: Water or steam reaching the metal, including fire-fighting water
      consequence: The Stanford sheet says the substance reacts violently with water. Wikipedia says cold water reacts slowly and hot water quickly, so the rate depends on temperature and form.
      severity: critical
      source: sam-pr-sds
      where: Section 10.3 Possibility of hazardous reactions
    - mode: Surface oxidation and flaking
      trigger: Long exposure to air
      consequence: The green oxide layer spalls like iron rust, and a centimetre-sized sample corrodes completely in about a year (Wikipedia).
      severity: low
      source: wikipedia-pr
      where: Reactions with air, first paragraph
    - mode: Fire fumes from oxide and combustion
      trigger: Burning the metal or heating it in air
      consequence: Fumes of praseodymium oxide are emitted in a fire, and the ACI sheet says irritating and toxic fumes and gases form on combustion.
      severity: moderate
      source: purdue-pr-sds
      where: Section 5 Specific hazards arising from the material
  side_effects:
    - text: Wikipedia says praseodymium is not very toxic. Intravenous injection of rare earths into animals has impaired liver function, and the main side effects of inhaling rare-earth oxides in humans come from radioactive thorium and uranium impurities.
      affects: Human health from inhaled oxide dust; purity of the metal
      source: wikipedia-pr
      where: Biological role and precautions section
  handling:
    - text: Store under argon or mineral oil in tightly closed containers, in a cool dry area, protected from moisture (Ames sheet; the ACI sheet says store under argon).
      source: purdue-pr-sds
      where: Section 7 Handling and Storage
    - text: Handle under inert gas and avoid contact with water (Stanford P231 and the ACI sheet, which says handle under an inert atmosphere).
      source: sam-pr-sds
      where: Section 2.2 Precautionary statements; Section 7 Handling and storage
    - text: Use a Class D dry powder extinguishing agent on fires. Do not use water (Ames sheet).
      source: purdue-pr-sds
      where: Section 5 Extinguishing media
    - text: Use dry sand, dry chemical or alcohol-resistant foam in a fire, and water spray only to cool unopened containers (Stanford sheet).
      source: sam-pr-sds
      where: Section 5.1 and 5.2 Extinguishing media and special hazards
    - text: For skin contact, brush off loose particles, then immerse in cool water or wrap in wet bandages (Stanford P335 and P334).
      source: sam-pr-sds
      where: Section 2.2 Precautionary statements
  mitigations: []
uses:
  - application: mechanisms
    device: Neodymium-praseodymium permanent magnets for motors, headphones and loudspeakers
    example: Wikipedia says praseodymium combined with neodymium makes high-power magnets, and that rare-earth alloys with 3d transition metals give very stable magnets used in motors, printers, watches, headphones and loudspeakers.
    source: wikipedia-pr
    where: Uses section, magnets bullet and the paragraph on magnets
  - application: optics-and-cameras
    device: Pr3+ doped lasers and fibre amplifiers
    example: Wikipedia lists Pr3+ as a dopant in DPSS lasers, single-mode fibre optical amplifiers and fibre lasers, and as an activator in red, green, blue and ultraviolet phosphors.
    source: wikipedia-pr
    where: Uses section, optics and photonics paragraph
  - application: structures
    device: Magnesium alloys with praseodymium for aircraft engine parts
    example: Wikipedia says praseodymium is alloyed with magnesium to make high-strength metals used in aircraft engines, and that yttrium and neodymium are suitable substitutes.
    source: wikipedia-pr
    where: Uses section, magnesium alloy bullet
supply:
  - subject: Praseodymium abundance
    abundance: 9.1 ppm of the Earth's crust (Wikipedia), similar to boron; the sixth most abundant rare earth
    producers: []
    critical_lists: []
    source: wikipedia-pr
    where: Occurrence paragraph, first sentences
  - subject: Rare earths, all rare-earth oxide (REO) equivalent; praseodymium 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.'
    substitutes:
      - 'USGS: substitutes are available for many rare-earth applications but generally are less effective.'
    source: usgs-re-2026
    where: World Mine Production and Reserves table, 2025 (world total 390,000 t REO; shares calculated by Space Mushroom against that total); Recycling; Substitutes
  - subject: 'Light rare earths (LREE group: cerium, lanthanum, neodymium, praseodymium, samarium), processing stage'
    producers:
      - country: China
        share_percent: 85
        year: 2023
    critical_lists:
      - list: 'EU Study on the Critical Raw Materials 2023: LREE group in the proposed list of 34 critical raw materials'
        listed: true
    recycling: Not stated in the EU study read.
    substitutes: []
    source: eu-crm-2023
    where: Grouped materials table, row LREEs (stage P, main global supplier China, share 85 %); list of 34 raw materials proposed for the CRM list 2023
  - subject: U.S. imports of rare-earth compounds and metals (group, not praseodymium alone), 2021 to 2024
    producers:
      - country: China
        share_percent: 71
        year: 2024
      - country: Malaysia
        share_percent: 13
        year: 2024
      - country: Japan
        share_percent: 5
        year: 2024
      - country: Estonia
        share_percent: 5
        year: 2024
    critical_lists: []
    source: usgs-re-2026
    where: Import Sources (2021-24) paragraph. These are import shares for all rare-earth compounds and metals, not production shares.
documents:
  - title: 'USGS Mineral Commodity Summaries, February 2026: Rare Earths'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf
    year: 2026
  - title: PubChem compound record for praseodymium (CID 23942), including ECHA C&L summary
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23942
    year: 2026
  - title: 'Wikipedia: Praseodymium'
    type: database
    url: https://en.wikipedia.org/wiki/Praseodymium
    year: 2026
  - title: ACI Alloys safety data sheet, praseodymium ingot 99.9 %
    type: sds
    url: https://www.acialloys.com/wp-content/uploads/msds/pr.html
    year: 2016
  - title: Praseodymium safety data sheet, Ames Laboratory copy hosted by Purdue PRIME Lab (revised 2016-01-26)
    type: sds
    url: https://www.physics.purdue.edu/primelab/safety/MSDS/SDS/praseodymium%20metal%20%20-Ames.pdf
    year: 2016
  - title: Safety data sheet, praseodymium metal, Stanford Advanced Materials
    type: sds
    url: https://www.samaterials.com/pdf/Praseodymium-Metal-(Pr-Metal)-sds.pdf
  - title: Safety data sheet, praseodymium powder -40 mesh, Apollo Scientific IN2953
    type: sds
    url: https://store.apolloscientific.co.uk/storage/msds/IN2953_msds.pdf
  - title: Study on the Critical Raw Materials for the EU 2023, final report
    type: report
    url: https://totalsupport.eu/_asset/_public/Downloads/study-on-the-critical-raw-materials-for-the-eu-2023-ET0723116ENN.pdf
    year: 2023
gaps:
  - 'Space use: no flight, vacuum, radiation or thermal-vacuum use of praseodymium metal was found in the sources read, so no environment tags are set.'
  - 'Praseodymium-only production and reserves: USGS reports rare earths as one group, so the world mine shares are for all rare earths, not praseodymium alone. The shares are calculated by Space Mushroom against the 390,000 t world total.'
  - 'Praseodymium-only import share: the U.S. import shares cover all rare-earth compounds and metals, not praseodymium alone.'
  - 'USGS critical minerals list: the USGS rare earths summary read here does not state a critical-minerals listing, and the 2025 USGS list was not opened, so no USGS listing is entered.'
  - 'Hardness: Vickers (250 to 745 MPa) and Brinell (250 to 640 MPa) are entered under the new names vickers_hardness and brinell_hardness, because the property file has no canonical name for hardness.'
  - 'Boiling point: PubChem and the ACI sheet give 3512 °C, the Ames and Stanford sheets give 3520 °C and the Wikipedia infobox gives 3130 °C. The PubChem value is entered and the difference is not reconciled.'
  - 'Density: 6.773 g/cm3 (Wikipedia, Ames) against 6.71 g/cm3 at 25 °C (Stanford) and 6.772 g/cm3 at 25 °C (PubChem). Both the Wikipedia and Stanford values are recorded.'
  - 'Thermal conductivity and electrical resistivity: only the Wikipedia infobox was read, and the infobox gives no temperature for thermal conductivity. American Elements (HTTP 403) and Thermo Fisher (HTTP 403) were not opened.'
  - 'Molar magnetic susceptibility, heat of fusion and heat of vaporization: no canonical names exist in the property file, so these are not entered.'
  - 'Hazard classification: PubChem (ECHA notifications) gives H228, H250, H251, H315, H319 and H413 for most reports, the Stanford and Apollo sheets classify the metal or powder as pyrophoric (H250), and the Ames and ACI sheets give no classification. Form and particle size appear to drive the difference. The Sigma-Aldrich sheet cited by Wikipedia was not opened.'
  - 'Ignition temperature of massive (non-powder) praseodymium in air: not given in the sources read. The 150 °C figure from Wikipedia is for the metal and is not tied to a form.'
  - 'Aqueous corrosion rates: no quantitative rate in water or humid air was found. The one-year figure for a centimetre-sized sample comes from Wikipedia, which cites a test page that was not opened.'
  - 'Designations: no UNS, ASTM, EN or other grade code for praseodymium metal was found in the sources read, so identity.designations is left out.'
  - 'Process: Wikipedia says the oxalates are burned to oxides and then reduced to metal, but the reduction route (for example calciothermic or electrolytic) is not stated in the text read.'
  - 'Price: USGS gives praseodymium oxide 99.99 % at 74 dollars per kg in 2025 (estimated), 56 in 2024 and 128 in 2022. The price is recorded in the story only, not as a property.'
  - 'Media: no photograph or diagram was added, because no image with a usable licence was opened in this run.'
  - 'Taxonomy: src/data/taxonomy.ts has no rare-earth type under metals. heavy-metals was chosen as the closest type; a rare-earth type would fit better.'
sources:
  usgs-re-2026:
    title: 'Mineral Commodity Summaries, February 2026: Rare Earths (USGS)'
    id: USGS MCS 2026, prepared by Shelby N. Johnston
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  pubchem-pr:
    title: 'PubChem compound record: Praseodymium (CID 23942), including ECHA C&L Inventory classification'
    id: CAS 7440-10-0
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23942/JSON
    kind: database
    license: PubChem (NCBI), public domain; sections attributed to ECHA and others
  wikipedia-pr:
    title: Praseodymium (Wikipedia)
    url: https://en.wikipedia.org/wiki/Praseodymium
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  aci-pr-sds:
    title: 'Safety data sheet: Praseodymium ingot, 99.9 % (ACI Alloys Inc.), revision 2 dated 2016-08-02'
    url: https://www.acialloys.com/wp-content/uploads/msds/pr.html
    year: 2016
    kind: datasheet
    license: supplier safety data sheet, cited not reproduced
  purdue-pr-sds:
    title: 'Safety data sheet: Praseodymium (Ames copy hosted by Purdue PRIME Lab, revised 2016-01-26)'
    url: https://www.physics.purdue.edu/primelab/safety/MSDS/SDS/praseodymium%20metal%20%20-Ames.pdf
    year: 2016
    kind: datasheet
    license: supplier safety data sheet, cited not reproduced
  sam-pr-sds:
    title: 'Safety data sheet: Praseodymium metal (Stanford Advanced Materials)'
    url: https://www.samaterials.com/pdf/Praseodymium-Metal-(Pr-Metal)-sds.pdf
    kind: datasheet
    license: supplier safety data sheet, cited not reproduced
  apollo-pr-sds:
    title: 'Safety data sheet: Praseodymium, powder -40 mesh (Apollo Scientific, IN2953)'
    url: https://store.apolloscientific.co.uk/storage/msds/IN2953_msds.pdf
    kind: datasheet
    license: supplier safety data sheet, cited not reproduced
  eu-crm-2023:
    title: Study on the Critical Raw Materials for the EU 2023, Final Report
    url: https://totalsupport.eu/_asset/_public/Downloads/study-on-the-critical-raw-materials-for-the-eu-2023-ET0723116ENN.pdf
    year: 2023
    kind: report
    license: EU study, cited not reproduced
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 14
  unreachable: 3
  caveats: 5
  note: 'Values were read by an AI assistant on 2026-10-26 from the pages and PDFs named in each entry. Unreachable: American Elements (HTTP 403), Thermo Fisher (HTTP 403), Sigma-Aldrich SDS (not found in search). Caveats: most physical values come from the Wikipedia infobox, which cites Arblaster 2018 without a fetched copy; the boiling point differs by up to 390 degrees C between sources; the hazard class differs by supplier sheet and form; the supply shares are rare-earth group shares, not praseodymium-only shares.'
story:
  risk_groups:
    - title: For people
      lead: The hazard depends on form. Solid praseodymium has few known health effects, but fine powder and chips can catch fire, and the supplier sheets disagree on the classification.
      level: 1
      verdict: Form-dependent
      points:
        - label: Powder and chips
          line: The 40-mesh powder (Apollo) and the metal (Stanford) are classed as pyrophoric, H250, while the Ames sheet gives no classification.
        - label: Dust and fumes
          line: Grinding, melting or welding can create dust or fumes (Ames). Under normal handling, solid forms present few health hazards.
        - label: Health
          line: Wikipedia says praseodymium is not very toxic. The main inhalation risk from rare-earth oxides comes from radioactive thorium and uranium impurities.
    - title: If it fails
      lead: 'The sources give three failure routes: a fire in fines, a reaction with water, and slow oxidation in air.'
      points:
        - label: Fire in fines
          line: Apollo classes the 40-mesh powder as pyrophoric, H250, and Stanford gives the same class for the metal.
        - label: Water
          line: Stanford says the metal reacts violently with water. Wikipedia says cold water reacts slowly and hot water quickly.
        - label: Air
          line: Wikipedia says a centimetre-sized sample corrodes completely in about a year, and that the metal burns readily at 150 °C.
    - title: Handling and storage
      points:
        - label: Keep it dry and under inert gas
          line: The ACI sheet says store under argon and protect from moisture. The Ames sheet says store under argon or mineral oil.
        - label: Fire
          line: Use a Class D dry powder agent (Ames), or dry sand, dry chemical or alcohol-resistant foam (Stanford). Do not use water.
  why: Praseodymium's value comes from its magnetic and optical behaviour. USGS reports magnets as the leading global end use of rare earths. Pr3+ ions are used as dopants in lasers and fibre amplifiers (Wikipedia). USGS prices praseodymium oxide 99.99 % at 74 dollars per kg in 2025 (estimated), against 128 in 2022, so the market moves with supply.
  uses:
    - where: NdPr magnets
      line: Praseodymium with neodymium makes high-power permanent magnets for motors, headphones and loudspeakers (Wikipedia).
    - where: Lasers and fibre amplifiers
      line: Pr3+ is a dopant in DPSS lasers, single-mode fibre amplifiers and fibre lasers (Wikipedia).
    - where: Aircraft engine alloys
      line: Praseodymium alloyed with magnesium gives high-strength metals used in aircraft engines (Wikipedia).
  can_do:
    - label: Weight
      value: 6.773 g/cm3
      benchmark: density
      line: Density is 6.773 g/cm3 at 20 °C (Wikipedia). The Stanford sheet gives 6.71 g/cm3 at 25 °C.
    - label: Melting
      value: 931 °C
      benchmark: melting_point
      line: Melting point is 931 °C (Wikipedia), and the ACI and Stanford sheets print the same figure.
    - label: Stiffness
      value: 37.3 GPa
      benchmark: elastic_modulus
      line: Young's modulus is 37.3 GPa, with shear modulus 14.8 GPa and bulk modulus 28.8 GPa (Wikipedia infobox).
    - label: Carries heat
      value: 12.5 W/(m·K)
      benchmark: thermal_conductivity
      line: Thermal conductivity is 12.5 W/(m·K) at a temperature the infobox does not state (Wikipedia).
    - label: Hardness
      value: 250 to 745 MPa
      benchmark: vickers_hardness
      line: Vickers hardness runs from 250 to 745 MPa (Wikipedia), and Wikipedia says the metal is ductile and about as hard as silver.
    - label: Magnetism
      value: paramagnetic
      line: Praseodymium is paramagnetic at all temperatures above 1 K (Wikipedia).
  compare: 'Wikipedia says praseodymium can replace most other lanthanides in their applications with little loss of function, and that it is one of the larger lanthanides. This profile has no second metal in the table, so read the rows as praseodymium values only. The hazard classes and supply shares above should be read the same way: they are praseodymium-group figures from the sources named, not a comparison.'
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  recipe:
    line: Praseodymium is a single-element metal (Pr) with a double hexagonal close-packed structure at room temperature (Wikipedia). It is not mined alone. Hot concentrated sulfuric acid treats the ore, the rare earths are separated by ion-exchange chromatography or by solvent extraction with tributyl phosphate, then precipitated as oxalates, burned to oxides and reduced to metal (Wikipedia).
    parts:
      - name: Praseodymium
        symbol: Pr
        atoms: 1
        atomic_weight: 140.90766
        role: The whole material. Praseodymium has one stable isotope, Pr-141 (Wikipedia). Atomic weight from PubChem (CID 23942).
  handling:
    - Store under argon or mineral oil in tightly closed containers, protected from moisture (Ames sheet; ACI says store under argon).
    - Handle under inert gas and keep away from water (Stanford P231; ACI says handle under an inert atmosphere).
    - Use a Class D dry powder extinguisher on fires, and never water (Ames sheet).
    - Brush loose particles off skin, then immerse in cool water or wrap in wet bandages (Stanford P335 and P334).
  good_for:
    - 'Magnets: NdPr alloys for high-power permanent magnets (Wikipedia; USGS).'
    - 'Optical gain: Pr3+ dopant in lasers and fibre amplifiers (Wikipedia).'
    - 'Aircraft engine alloys: magnesium-praseodymium alloys for high-strength parts (Wikipedia).'
  watch_out:
    - Fine powder and chips are pyrophoric in the Apollo and Stanford sheets, while the Ames and ACI sheets give no hazard class. Check the sheet for the exact form you handle.
    - 'Supply is concentrated: China is 85 % of LREE processing (EU 2023 study) and 69.2 % of world rare-earth mine output in 2025 (USGS, calculated).'
    - USGS names samarium, gadolinium, terbium, dysprosium, lutetium, scandium and yttrium in China's 2025 export controls, but not praseodymium.
    - Melting point, density and boiling point vary by source, as the notes above show.
  verdict: 'Praseodymium is a magnet and optical rare-earth metal with a density of 6.773 g/cm3 and a melting point of 931 °C. Its main use is NdPr magnets, and its density and melting point agree within about 1 % across the sources read. The metal itself is a handling problem: fine powder is pyrophoric in two supplier sheets, and the metal reacts with water and tarnishes in air. No flight or space-qualified use was found.'