Platinum-iridium alloy Pt-Ir

spore: profile
id: platinum-iridium
spore_version: 0.2
family: precious-metals
name: Platinum-iridium alloy
abbreviation: Pt-Ir
role: standards, electrodes and thermocouple wire
category: metals
type: precious-metals
summary: |
  Platinum-iridium is a ductile precious-metal alloy, most often 90 % platinum and 10 % iridium (Pt-10Ir). The Heraeus datasheet for PtIr10 gives a density of 21.54 g/cm3 and a melting range of 1790 to 1800 °C. The harder PtIr20 grade has a density of 21.7 g/cm3 and a melting range of 1830 to 1855 °C. The international kilogram prototype is made of 90 % platinum and 10 % iridium, and the 1985 NIST paper gives a density of 21.55 g/cm3 for the prototypes. Heraeus lists PtIr10 for thermocouples, electrodes and spark plug electrodes, and PtIr20 for medical wire and probe needles. No space-electrode source was found in this run.
best_for: Reference artefacts and electrodes that need a dense, hard, stable metal. The kilogram and metre prototypes were made of it, and the alloy is harder than pure platinum.
weakest_at: Heavy for its size (21.54 g/cm3 for PtIr10) and soft when annealed (105 HV for PtIr10)
identity:
  formula: Pt-10Ir, 90 % platinum and 10 % iridium by mass (the kilogram prototype alloy); Pt-20Ir is the Heraeus PtIr20 grade
  source: nist-v90-4
  where: 'Section 1 (Introduction), page 263: the IPK is made of an alloy of 90% platinum and 10% iridium. Heraeus designations PtIr10 (Hera 173) and PtIr20 (Hera 174).'
tags:
  environments: []
  stresses: []
  applications:
    - thermal-control
    - propulsion-and-tanks
    - electronics-and-chips
properties:
  - benchmark: density
    label: Density, PtIr10 (Heraeus Hera 173)
    value: 21.54
    unit: g/cm3
    scope: material
    conditions:
      form: PtIr10 wire and sheet (Heraeus product forms)
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: General information table, row Density, g/cm³
  - benchmark: density
    label: Density, PtIr20 (Heraeus Hera 174)
    value: 21.7
    unit: g/cm3
    scope: material
    conditions:
      form: PtIr20 wire (Heraeus product forms)
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: General information table, row Density, g/cm³
  - benchmark: density
    label: Density of the national prototype kilograms (NIST paper)
    value: 21.55
    unit: g/cm3
    scope: material
    conditions:
      form: platinum-iridium prototype kilograms (90 % Pt, 10 % Ir)
      temperature: not stated in the text
    method: Value printed in a 1985 NIST journal paper on the prototype kilogram
    status: ground
    source: nist-v90-4
    where: Section 1 (Introduction), page 263, paragraph on the nichrome working standards
  - benchmark: melting_point
    label: Melting range, PtIr10 (Heraeus Hera 173)
    value: 1790
    value_high: 1800
    bound: range
    unit: °C
    scope: material
    conditions:
      form: PtIr10 wire and sheet
      pressure: not stated
    method: Range printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: General information table, row Melting Range, °C
  - benchmark: melting_point
    label: Melting range, PtIr20 (Heraeus Hera 174)
    value: 1830
    value_high: 1855
    bound: range
    unit: °C
    scope: material
    conditions:
      form: PtIr20 wire
      pressure: not stated
    method: Range printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: General information table, row Melting Range, °C
  - benchmark: elastic_modulus
    label: Young's modulus, PtIr10 (Heraeus Hera 173)
    value: 202.3
    unit: GPa
    scope: material
    conditions:
      form: PtIr10 wire and sheet
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, row Young's Modulus, GPa
  - benchmark: elastic_modulus
    label: Young's modulus, PtIr20 (Heraeus Hera 174)
    value: 255
    unit: GPa
    scope: material
    conditions:
      form: PtIr20 wire
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, row Young's Modulus, GPa
  - benchmark: shear_modulus
    label: Modulus of rigidity, PtIr10 (Heraeus Hera 173)
    value: 73.4
    unit: GPa
    scope: material
    conditions:
      form: PtIr10 wire and sheet
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, row Modulus of Rigidity, GPa
  - benchmark: shear_modulus
    label: Modulus of rigidity, PtIr20 (Heraeus Hera 174)
    value: 86
    unit: GPa
    scope: material
    conditions:
      form: PtIr20 wire
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, row Modulus of Rigidity, GPa
  - benchmark: electrical_conductivity
    label: Electrical conductivity range, PtIr10 (Heraeus Hera 173)
    value: 6.83
    value_high: 7.02
    bound: range
    unit: '% IACS'
    scope: material
    conditions:
      form: PtIr10 wire and sheet
      temperature: not stated in the table
    method: Minimum and maximum printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, rows Conductivity, min., % IACS and Conductivity, max., % IACS
  - benchmark: electrical_conductivity
    label: Electrical conductivity range, PtIr20 (Heraeus Hera 174)
    value: 5.38
    value_high: 5.55
    bound: range
    unit: '% IACS'
    scope: material
    conditions:
      form: PtIr20 wire
      temperature: not stated in the table
    method: Minimum and maximum printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, rows Conductivity, min., % IACS and Conductivity, max., % IACS
  - benchmark: vickers_hardness
    label: Hardness HV, PtIr10 annealed (Heraeus Hera 173)
    value: 105
    unit: HV
    scope: material
    conditions:
      temper: annealed
      form: PtIr10 wire and sheet
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, row Hardness, HV, column Annealed
  - benchmark: vickers_hardness
    label: Hardness HV, PtIr10 work hardened (Heraeus Hera 173)
    value: 215
    unit: HV
    scope: material
    conditions:
      temper: work hardened
      form: PtIr10 wire and sheet
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, row Hardness, HV, column Work Hardened
  - benchmark: vickers_hardness
    label: Hardness HV, PtIr20 annealed (Heraeus Hera 174)
    value: 190
    unit: HV
    scope: material
    conditions:
      temper: annealed
      form: PtIr20 wire
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, row Hardness, HV, column Annealed
  - benchmark: vickers_hardness
    label: Hardness HV, PtIr20 work hardened (Heraeus Hera 174)
    value: 300
    unit: HV
    scope: material
    conditions:
      temper: work hardened
      form: PtIr20 wire
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, row Hardness, HV, column Work Hardened
  - benchmark: yield_strength
    label: Yield strength, PtIr10 annealed (Heraeus Hera 173)
    value: 220
    unit: MPa
    scope: material
    conditions:
      temper: annealed
      form: PtIr10 wire and sheet
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, row Yield Strength, MPa, column Annealed
  - benchmark: yield_strength
    label: Yield strength, PtIr10 work hardened (Heraeus Hera 173)
    value: 630
    unit: MPa
    scope: material
    conditions:
      temper: work hardened
      form: PtIr10 wire and sheet
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, row Yield Strength, MPa, column Work Hardened
  - benchmark: yield_strength
    label: Yield strength, PtIr20 annealed (Heraeus Hera 174)
    value: 380
    unit: MPa
    scope: material
    conditions:
      temper: annealed
      form: PtIr20 wire
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, row Yield Strength, MPa, column Annealed
  - benchmark: yield_strength
    label: Yield strength, PtIr20 work hardened (Heraeus Hera 174)
    value: 920
    unit: MPa
    scope: material
    conditions:
      temper: work hardened
      form: PtIr20 wire
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, row Yield Strength, MPa, column Work Hardened
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, PtIr10 annealed (Heraeus Hera 173)
    value: 340
    unit: MPa
    scope: material
    conditions:
      temper: annealed
      form: PtIr10 wire and sheet
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, row Tensile Strength, MPa, column Annealed
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, PtIr10 work hardened (Heraeus Hera 173)
    value: 650
    unit: MPa
    scope: material
    conditions:
      temper: work hardened
      form: PtIr10 wire and sheet
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, row Tensile Strength, MPa, column Work Hardened
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, PtIr20 annealed (Heraeus Hera 174)
    value: 570
    unit: MPa
    scope: material
    conditions:
      temper: annealed
      form: PtIr20 wire
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, row Tensile Strength, MPa, column Annealed
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, PtIr20 work hardened (Heraeus Hera 174)
    value: 940
    unit: MPa
    scope: material
    conditions:
      temper: work hardened
      form: PtIr20 wire
      temperature: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, row Tensile Strength, MPa, column Work Hardened
  - benchmark: elongation
    label: Elongation, PtIr10 annealed (Heraeus Hera 173)
    value: 32
    unit: '%'
    scope: material
    conditions:
      temper: annealed
      form: PtIr10 wire and sheet
      gauge_length: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, row Elongation, %, column Annealed
  - benchmark: elongation
    label: Elongation, PtIr10 work hardened (Heraeus Hera 173)
    value: 2
    unit: '%'
    scope: material
    conditions:
      temper: work hardened
      form: PtIr10 wire and sheet
      gauge_length: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt10ir
    where: Physical properties table, row Elongation, %, column Work Hardened
  - benchmark: elongation
    label: Elongation, PtIr20 annealed (Heraeus Hera 174)
    value: 21
    unit: '%'
    scope: material
    conditions:
      temper: annealed
      form: PtIr20 wire
      gauge_length: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, row Elongation, %, column Annealed
  - benchmark: elongation
    label: Elongation, PtIr20 work hardened (Heraeus Hera 174)
    value: 2
    unit: '%'
    scope: material
    conditions:
      temper: work hardened
      form: PtIr20 wire
      gauge_length: not stated in the table
    method: Value printed in a manufacturer datasheet
    status: ground
    source: heraeus-pt20ir
    where: Physical properties table, row Elongation, %, column Work Hardened
  - benchmark: charge_injection_capacity
    label: Charge injection of electrodeposited PtIr on carbon fibre
    value: 1.25
    unit: mC/cm2
    scope: material
    conditions:
      form: electrodeposited PtIr coating on carbon fibre microelectrodes (not a bulk alloy)
      pulse: 0.5 ms pulses
      electrolyte: 1x PBS (0.01 M phosphate buffered saline)
    method: Value printed in a 2021 open-access paper, section 4; the paper calls it the highest density tested
    status: ground
    note: Benchmark name is not in the canonical file; it is a coating result on carbon fibre, not a bulk-alloy value.
    source: frontiers-ptir
    where: Section 4 (Discussion or conclusion), charge injection sentence
corrosion:
  - environment: Storage and handling of the kilogram prototype (airborne pollutants and mercury vapour)
    headline: The kilogram prototype loses about 50 μg against its copies over a century, mostly from contamination.
    effect: The Wikipedia article says the IPK lost perhaps 50 μg relative to its official copies over the last century. Cleaning removes between 5 and 60 μg of contamination, and the article links the drift to mercury absorbed near mercury-based instruments.
    rating: low
    conditions:
      basis: mass drift relative to official copies, not a corrosion rate
      cleaning: rubbing with ether and ethanol, then steam (as the article describes)
    source: wikipedia-ipk
    where: Stability of the IPK section and cleaning passage
  - environment: Repeated electrical stimulation in phosphate-buffered saline (PtIr coating on carbon fibre)
    headline: No coating loss or delamination was seen after stimulation tests.
    effect: The paper says that in all stimulation experiments, SEM inspection found no coating loss or delamination. It did not measure corrosion or dissolution of Pt or Ir.
    rating: low
    conditions:
      electrolyte: 1x PBS
      basis: visual and SEM inspection after pulse tests; no mass loss or dissolution measured
    source: frontiers-ptir
    where: Section 4 (stability finding)
  - environment: General use, as listed by the manufacturer
    headline: Heraeus lists PtIr20 as corrosion resistant, with no test conditions.
    effect: The Hera 174 datasheet lists PtIr20 under chemical properties as corrosion resistant. It gives no environment, test method or corrosion rate.
    rating: low
    conditions:
      basis: qualitative datasheet statement only
    source: heraeus-pt20ir
    where: Chemical properties section
risks:
  hazards:
    - text: 'PubChem iridium record (CID 23924): 36.9 % of company reports (92 of 249) do not meet GHS criteria. Notified codes are H228 (18.1 %, flammable solid), H319 (20.1 %, serious eye irritation) and H413 (41.8 %, long-lasting harmful effects to aquatic life), with signal word Danger.'
      ghs:
        - H228
        - H319
        - H413
      source: pubchem-ir
      where: Safety and Hazards, GHS Classification, ECHA C&L Notifications Summary
    - text: 'PubChem platinum record (CID 23939): 81.3 % of company reports (410 of 504) do not meet GHS criteria. H228 (10.7 %, flammable solid) is shown, with signal word Danger.'
      ghs:
        - H228
      source: pubchem-pt
      where: Safety and Hazards, GHS Classification, ECHA C&L Notifications Summary
    - text: The same platinum record lists H315, H319, H334 and H335 from 94 of 504 company reports that gave hazard codes. H334 is respiratory sensitisation.
      ghs:
        - H315
        - H319
        - H334
        - H335
      source: pubchem-pt
      where: Safety and Hazards, GHS Classification, second notification block
  failure_risks:
    - mode: Cracking of an electrodeposited PtIr film at a microelectrode tip
      trigger: Preliminary in vivo stimulation of visual cortex and spinal cord in the 2021 study
      consequence: The paper reports a crack in the PtIr film near the tip after in vivo stimulation, and says it is more likely from deposition, handling or SEM preparation. It is a single preliminary observation.
      severity: low
      source: frontiers-ptir
      where: Section 3.3
  side_effects:
    - text: PtIr10 has a density of 21.54 g/cm3, so parts are heavy for their volume.
      affects: Mass of an electrode, contact or prototype
      source: heraeus-pt10ir
      where: General information table, row Density
  handling:
    - text: PubChem precautionary codes for the iridium element record include P210, P240, P241, P280 and P370+P378 among a longer list, with the H228 flammable-solid classification.
      source: pubchem-ir
      where: Hazards Identification, Precautionary Statement Codes
    - text: The Hera 174 datasheet lists PtIr20 as formable, machinable and able to be roll clad.
      source: heraeus-pt20ir
      where: Forming Process row
  mitigations: []
uses:
  - application: thermal-control
    device: Thermocouples and electrodes (PtIr10 product listing)
    example: Heraeus lists PtIr10 for thermocouples, electrodes and spark plug electrodes, in wire and sheet form.
    source: heraeus-pt10ir
    where: General information table, row Applications
  - application: propulsion-and-tanks
    device: Spark plug electrodes
    example: Heraeus lists both PtIr10 and PtIr20 for spark plug electrodes. The PtIr20 listing also includes contacts and sliding contacts.
    source: heraeus-pt20ir
    where: General information table, row Applications
  - application: electronics-and-chips
    device: Medical wire and probe needles
    example: Heraeus lists PtIr20 for medical wire and probe needles, as well as contacts and electrodes.
    source: heraeus-pt20ir
    where: General information table, row Applications
  - application: electronics-and-chips
    device: Microelectrodes for neural stimulation (research, preliminary)
    example: A 2021 study electrodeposited PtIr on carbon fibre microelectrodes and tested them for visual cortex and spinal cord stimulation. The authors call the in vivo work preliminary.
    source: frontiers-ptir
    where: Introduction and Section 4
supply:
  - subject: Platinum (world mine production and recycling, used for the Pt content)
    producers:
      - country: South Africa
        share_percent: 70.6
        year: 2025
      - country: Russia
        share_percent: 11.8
        year: 2025
      - country: Zimbabwe
        share_percent: 10.6
        year: 2025
      - country: Canada
        share_percent: 2.9
        year: 2025
      - country: United States
        share_percent: 1.1
        year: 2025
    critical_lists:
      - list: USGS Final 2025 List of Critical Minerals (platinum-group metals chapter)
        listed: true
    recycling: 'USGS: about 140,000 kg of palladium and platinum were recovered globally from new and old scrap in 2025.'
    substitutes: []
    source: usgs-mcs2026-pgm
    where: World Mine Production and Reserves table, platinum 2025e (South Africa 120,000 kg, Russia 20,000 kg, Zimbabwe 18,000 kg, Canada 5,000 kg, United States 1,800 kg, world total 170,000 kg). Shares are calculated by Space Mushroom from those kilogram values. Recycling paragraph, PGM chapter, page 145.
  - subject: Iridium (United States imports and price; no world mine production in the chapter)
    abundance: United States imports of iridium were 2,200 kg in 2025e. The 2025e price was 4,400 dollars per troy ounce.
    producers: []
    critical_lists:
      - list: 'USGS MCS 2026 footnote: iridium is among the critical minerals published in the Federal Register on November 7, 2025, but is not shown in the production table'
        listed: true
    recycling: Not read in this run.
    substitutes: []
    source: usgs-mcs2026-pgm
    where: Salient Statistics table (imports for consumption, iridium 2025e); Price table, dollars per troy ounce; footnote on critical minerals in the Mineral Commodity Summaries table
documents:
  - title: Heraeus Precious Metals, PtIr10 (Hera 173) datasheet, status 11/2021
    type: datasheet
    url: https://pim.heraeus.com/datasheets/HPM/FM/Contact%20Materials/Hera_173_Datasheet_EN_(Heraeus_Precious_Metals).pdf
    year: 2021
  - title: Heraeus Precious Metals, PtIr20 (Hera 174) datasheet, status 09/2021
    type: datasheet
    url: https://pim.heraeus.com/datasheets/HPM/FM/Contact%20Materials/Hera_174_Datasheet_EN_(Heraeus_Precious_Metals).pdf
    year: 2021
  - title: Davis, Recalibration of the U.S. National Prototype Kilogram, J. Res. NBS 90(4), 1985
    type: paper
    url: https://nvlpubs.nist.gov/nistpubs/jres/090/4/V90-4.pdf
    year: 1985
  - title: 'Wikipedia: International Prototype of the Kilogram'
    type: database
    url: https://en.wikipedia.org/wiki/International_Prototype_of_the_Kilogram
    year: 2026
  - title: 'Wikipedia: Mètre des Archives (metre prototype)'
    type: database
    url: https://en.wikipedia.org/wiki/M%C3%A8tre_des_Archives
    year: 2026
  - title: PubChem compound record, Iridium (CID 23924), GHS classification
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23924/JSON
    year: 2026
  - title: PubChem compound record, Platinum (CID 23939), GHS classification
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23939/JSON
    year: 2026
  - title: USGS Mineral Commodity Summaries 2026, Platinum-Group Metals chapter
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026.pdf
    year: 2026
  - title: della Valle et al., Electrodeposited Platinum Iridium Enables Microstimulation With Carbon Fiber Electrodes, Frontiers in Nanotechnology, 2021
    type: paper
    url: https://www.frontiersin.org/journals/nanotechnology/articles/10.3389/fnano.2021.782883/full
    year: 2021
gaps:
  - No space-electrode source was found. The searches returned an Aerospace Corporation screen-embrittlement report (not read) and iridium and platinum alloys used to encapsulate radioisotope fuel pellets, which is not an electrode use and was not read in full.
  - No thermal conductivity, coefficient of thermal expansion, specific heat or Poisson ratio for Pt-Ir was found in a page read in this run.
  - No UNS, EN, DIN, JIS or ASTM designation for PtIr10 or PtIr20 was printed in a page read in this run. ASTM B684 was named only in an aggregator snippet and is not recorded.
  - The Heraeus datasheets give no temperature or test method for any property, so conditions are marked as not stated.
  - The metre bar density and hardness are not printed in the Wikipedia article read in this run, which gives only the composition, the X-shaped section, 16 mm by 16 mm by 102 cm dimensions and the hardness reason.
  - No application in the fixed application list fits metrology, so the kilogram and metre standards are described in the story but not in uses.
  - No pacing-lead or implant corrosion test on bulk Pt-Ir was read in this run. The corrosion entries are a datasheet statement, a prototype mass-drift figure and a coating study.
  - Hazard records are for the platinum and iridium elements, not for the alloy. No Pt-Ir alloy safety data sheet was read.
  - Iridium world mine production is not in the USGS PGM chapter, so the iridium supply entry gives United States imports and price only.
  - The charge injection benchmark and the hardness and electrical conductivity names are not in the canonical file. They are used as short snake_case or existing names and need adding to spores/property-canon.yaml.
  - 'No media entry: no image of a Pt-Ir prototype, electrode or datasheet figure was checked for licence in this run, so the media section is left out.'
  - Third-party sites give different PtIr10 tensile and hardness ranges. Those were not recorded; only the Heraeus datasheet values are used.
sources:
  heraeus-pt10ir:
    title: Hera 173, PtIr10, Heraeus Precious Metals datasheet (status 11/2021)
    url: https://pim.heraeus.com/datasheets/HPM/FM/Contact%20Materials/Hera_173_Datasheet_EN_(Heraeus_Precious_Metals).pdf
    year: 2021
    kind: datasheet
    license: Manufacturer datasheet (cited, not reproduced)
  heraeus-pt20ir:
    title: Hera 174, PtIr20, Heraeus Precious Metals datasheet (status 09/2021)
    url: https://pim.heraeus.com/datasheets/HPM/FM/Contact%20Materials/Hera_174_Datasheet_EN_(Heraeus_Precious_Metals).pdf
    year: 2021
    kind: datasheet
    license: Manufacturer datasheet (cited, not reproduced)
  nist-v90-4:
    title: Davis, Recalibration of the U.S. National Prototype Kilogram, Journal of Research of NBS, volume 90, number 4 (1985)
    url: https://nvlpubs.nist.gov/nistpubs/jres/090/4/V90-4.pdf
    year: 1985
    kind: paper
    license: public domain (NIST)
  wikipedia-ipk:
    title: 'Wikipedia: International Prototype of the Kilogram (composition, stability and cleaning sections)'
    url: https://en.wikipedia.org/wiki/International_Prototype_of_the_Kilogram
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  wikipedia-metre:
    title: 'Wikipedia: Mètre des Archives (metre prototype, composition and shape)'
    url: https://en.wikipedia.org/wiki/M%C3%A8tre_des_Archives
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  pubchem-ir:
    title: PubChem compound record, Iridium (CID 23924), GHS classification and CAS number
    id: CID 23924, CAS 7439-88-5
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23924/JSON
    kind: database
    license: PubChem (NCBI), public domain; sections attributed to ECHA and others
  pubchem-pt:
    title: PubChem compound record, Platinum (CID 23939), GHS classification and CAS number
    id: CID 23939, CAS 7440-06-4
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23939/JSON
    kind: database
    license: PubChem (NCBI), public domain; sections attributed to ECHA and others
  usgs-mcs2026-pgm:
    title: Mineral Commodity Summaries 2026, Platinum-Group Metals chapter (U.S. Geological Survey, February 2026)
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  frontiers-ptir:
    title: Electrodeposited Platinum Iridium Enables Microstimulation With Carbon Fiber Electrodes (Frontiers in Nanotechnology, 2021)
    id: doi:10.3389/fnano.2021.782883
    url: https://www.frontiersin.org/journals/nanotechnology/articles/10.3389/fnano.2021.782883/full
    year: 2021
    kind: paper
    license: open access (cited, not reproduced)
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 28
  unreachable: 1
  caveats: 6
  note: 'Values were read by an AI assistant on 2026-10-26 from the Heraeus datasheets, the NIST paper, Wikipedia, PubChem, the USGS MCS 2026 PGM chapter and one 2021 paper. Unreachable: the Heraeus product page and the Matthey article (403). Caveats: the datasheets give no temperatures; the metre prototype figures are secondary; the charge injection value is for a coating on carbon fibre; the platinum shares are calculated from kilogram values; no space-electrode source; the hazard records are for the elements.'
story:
  recipe:
    line: Pt-10Ir is a binary alloy of platinum and iridium, 90 % platinum and 10 % iridium by mass. The NIST paper says the ingots of the kilogram prototype were swaged until their density reached a maximum. The Wikipedia article says the metre bar was made in an X-shaped section from the same alloy.
    parts:
      - name: Platinum
        symbol: Pt
        share_percent: 90
        role: The main component. It gives the alloy its high density (21.54 g/cm3 for PtIr10 in the Heraeus datasheet).
      - name: Iridium
        symbol: Ir
        share_percent: 10
        role: Added to raise the hardness. The Wikipedia article says the alloy is significantly harder than pure platinum.
  risk_groups:
    - title: For people
      level: 1
      verdict: Mixed element records
      lead: The platinum and iridium element records carry flammable-solid and irritation codes in some company reports. The alloy has no record of its own.
      points:
        - label: Platinum element
          line: Of 504 company reports, 410 said platinum does not meet GHS criteria. H228 (flammable solid, 10.7 %) is shown with the signal word Danger, and H334 (respiratory sensitisation) comes from 94 of 504 reports.
        - label: Iridium element
          line: Of 249 company reports, 92 said iridium does not meet GHS criteria. H228 (18.1 %), H319 (20.1 %) and H413 (41.8 %) are shown, with the signal word Danger.
    - title: If it fails
      lead: The only failure route in a read source is a coating crack, found in a preliminary test.
      points:
        - label: Coating crack
          line: The 2021 study reports a crack in the PtIr film near the electrode tip after in vivo stimulation. The authors think deposition, handling or SEM preparation more likely caused it.
    - title: Handling and storage
      points:
        - label: Fine forms
          line: PubChem gives H228 (flammable solid) for both element records, so keep fine forms away from heat and ignition sources.
        - label: Cleaning the prototype
          line: The Wikipedia article describes cleaning with ether and ethanol, then steam. It says cleaning removes between 5 and 60 μg of contamination.
  why: Platinum-iridium is used where a dense, hard and stable metal is needed. The kilogram prototype is made of 90 % platinum and 10 % iridium, and the metre bar was made from a similar alloy by the BIPM with Johnson Matthey. The Wikipedia article says the alloy is harder than pure platinum, and Heraeus lists PtIr10 for thermocouples, electrodes and spark plug electrodes. PtIr20 is listed for medical wire and probe needles. In a 2021 study, electrodeposited PtIr on carbon fibre stimulated tissue in a preliminary test.
  uses:
    - where: Thermocouples and spark plugs
      line: Heraeus lists PtIr10 for thermocouples, electrodes and spark plug electrodes, in wire and sheet form.
    - where: Medical wire and probe needles
      line: Heraeus lists PtIr20 for medical wire and probe needles, as well as contacts and electrodes.
    - where: Microelectrodes (research, preliminary)
      line: A 2021 study electrodeposited PtIr on carbon fibre microelectrodes and tested them for visual cortex and spinal cord stimulation. The authors call the in vivo work preliminary.
  can_do:
    - label: Density
      value: 21.54 g/cm3
      benchmark: density
      line: PtIr10 has a density of 21.54 g/cm3 in the Heraeus datasheet. The NIST paper gives 21.55 g/cm3 for the national prototypes.
    - label: Melting
      value: 1790 to 1800 °C
      benchmark: melting_point
      line: The PtIr10 melting range is 1790 to 1800 °C. The PtIr20 range is 1830 to 1855 °C.
    - label: Hardness
      value: 215 HV work hardened
      benchmark: vickers_hardness
      line: PtIr10 is 105 HV annealed and 215 HV work hardened. PtIr20 is 190 HV annealed and 300 HV work hardened.
    - label: Charge injection
      value: 1.25 mC/cm2
      benchmark: charge_injection_capacity
      line: Electrodeposited PtIr on carbon fibre injected 1.25 mC/cm2 in 0.5 ms pulses in PBS, the highest density tested in that study.
  compare: The Heraeus datasheets show that moving from PtIr10 to PtIr20 raises the density, melting range, Young's modulus and hardness, and lowers the electrical conductivity. The rows below compare the two grades, not other materials.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Young's modulus
      benchmark: elastic_modulus
  handling:
    - State the temper with every strength value. PtIr10 yield strength is 220 MPa annealed and 630 MPa work hardened.
    - Keep fine forms away from heat and ignition sources, since PubChem gives H228 for the element records.
    - Clean the surface gently. The Wikipedia article describes rubbing with ether and ethanol, then steam, for the kilogram prototype.
  good_for:
    - Reference artefacts where a stable, dense metal matters. The kilogram prototype is 90 % platinum and 10 % iridium.
    - Thermocouple and spark plug electrodes, as listed by Heraeus for PtIr10.
    - Medical wire and probe needles, as listed by Heraeus for PtIr20.
  watch_out:
    - Annealed PtIr10 is soft at 105 HV. Work hardening raises it to 215 HV but cuts elongation to 2 %.
    - Surface contamination moves the mass of the kilogram prototype. The Wikipedia article gives about 50 μg lost over a century against its copies.
    - No space-electrode source, thermal conductivity, expansion or outgassing value was read for the alloy in this run.
  verdict: Platinum-iridium is a dense, hard and stable platinum alloy. PtIr10 is the standard composition, and PtIr20 is the harder grade. The datasheets and the NIST paper give density, mechanical and conductivity values, but the space-electrode use and the thermal properties remain unsourced.