spore: profile
id: platinum-rhodium
spore_version: 0.2
family: precious-metals
name: Platinum-rhodium alloys
abbreviation: Pt-Rh
role: thermocouple elements and glass-fibre bushing alloy for high temperatures
category: metals
type: precious-metals
summary: |
  Platinum-rhodium alloys are platinum with 10, 13 or 30 wt% rhodium. They are the thermoelements of the standard noble-metal thermocouples: Type S (Pt-10Rh against Pt), Type R (Pt-13Rh against Pt) and Type B (Pt-30Rh against Pt-6Rh), as NIST Monograph 175 defines them. At 1000 °C the NIST reference table gives 9.587 mV for Type S and 10.506 mV for Type R, measured against a 0 °C reference junction. Heraeus gives melting ranges of 1840 to 1870 °C for Pt-10Rh and 1920 to 1925 °C for Pt-30Rh. In NASA drift tests at 1500 to 1600 K, an 87Pt13Rh against Pt couple drifted about 5 K in air over 10,000 h and about 22 K in argon.
best_for: 'High-temperature thermocouples in air or other oxidizing and neutral atmospheres: NIST gives a standard range of -50 to 1768 °C for Types R and S and 0 to 1820 °C for Type B'
weakest_at: 'Reducing atmospheres and silicon contamination at high temperature (NBS Monograph 40), grain growth and drift above about 1200 °C (Edler et al. 2021), and cost: USGS gives rhodium at 5,800 dollars per troy ounce in 2025e'
identity:
  formula: 'Binary platinum-rhodium alloys: Pt-10 wt% Rh (Type S leg), Pt-13 wt% Rh (Type R leg) and Pt-30 wt% Rh (Type B leg); no single CAS number covers the alloy family'
  source: nist-m175
  where: Table 1.1.1 (type designations, temperature ranges and alloy pairs); Tables B3.1.1 and B4.1.1 for the Type R and S alloy pairs
tags:
  environments: []
  stresses: []
  applications:
    - thermal-control
properties:
  - benchmark: thermoelectric_emf
    label: EMF of the Type S couple (Pt-10Rh against Pt) at 1000 °C
    value: 9.587
    unit: mV
    scope: material
    conditions:
      couple: Type S, platinum-10% rhodium versus platinum
      reference_junction: 0 °C
      scale: ITS-90
      temperature: 1000 °C
    method: Reference-table value printed in NIST Monograph 175
    status: ground
    source: nist-m175
    where: Table B4.1.1 (Type S thermoelectric voltage as a function of temperature in °C), row 1000
  - benchmark: thermoelectric_emf
    label: EMF of the Type R couple (Pt-13Rh against Pt) at 1000 °C
    value: 10.506
    unit: mV
    scope: material
    conditions:
      couple: Type R, platinum-13% rhodium versus platinum
      reference_junction: 0 °C
      scale: ITS-90
      temperature: 1000 °C
    method: Reference-table value printed in NIST Monograph 175
    status: ground
    source: nist-m175
    where: Table B3.1.1 (Type R thermoelectric voltage as a function of temperature in °C), row 1000
  - benchmark: thermocouple_range
    label: Standard temperature range, Type R couple
    value: -50
    value_high: 1768
    bound: range
    unit: °C
    scope: material
    conditions:
      couple: Type R, platinum-13% rhodium versus platinum
      scale: ITS-90
    method: Range printed for the standardised thermocouple type; it is a calibration range, not a material limit
    status: ground
    source: nist-m175
    where: Table 1.1.1, row R
  - benchmark: thermocouple_range
    label: Standard temperature range, Type S couple
    value: -50
    value_high: 1768
    bound: range
    unit: °C
    scope: material
    conditions:
      couple: Type S, platinum-10% rhodium versus platinum
      scale: ITS-90
    method: Range printed for the standardised thermocouple type; it is a calibration range, not a material limit
    status: ground
    source: nist-m175
    where: Table 1.1.1, row S
  - benchmark: thermocouple_range
    label: Standard temperature range, Type B couple
    value: 0
    value_high: 1820
    bound: range
    unit: °C
    scope: material
    conditions:
      couple: Type B, platinum-30% rhodium versus platinum-6% rhodium
      scale: ITS-90
    method: Range printed for the standardised thermocouple type; it is a calibration range, not a material limit
    status: ground
    source: nist-m175
    where: Table 1.1.1, row B
  - benchmark: density
    label: Density of 10 wt% rhodium alloy at 20 °C
    value: 19.97
    unit: g/cm3
    scope: material
    conditions:
      composition: 10 wt% rhodium in platinum
      temperature: 20 °C
      form: not stated
    method: Tabulated value; the Heraeus Pt-10Rh datasheet prints the rounded figure 20
    status: ground
    source: nbs-m40
    where: Table 11, density at 20 °C, column 10 weight percent rhodium
  - benchmark: density
    label: Density of 13 wt% rhodium wire (supplier listing)
    value: 19.595
    unit: g/cm3
    scope: material
    conditions:
      composition: 13 wt% rhodium (87:13 Pt:Rh by weight), 0.5 mm wire
      temperature: not stated
    method: Density field of a supplier catalogue listing; no second source checked, and no temperature stated
    status: ground
    note: Only one source was found for the Pt-13Rh density. NBS Monograph 40 Table 11 has no 13 wt% row, so no value was interpolated.
    source: thermo-pt13rh
    where: Product details, Density field
  - benchmark: density
    label: Density of 30 wt% rhodium alloy at 20 °C
    value: 17.6
    unit: g/cm3
    scope: material
    conditions:
      composition: 30 wt% rhodium in platinum
      temperature: 20 °C
      form: not stated
    method: Tabulated value; the Heraeus Pt-30Rh datasheet prints the same figure 17.6 without a temperature
    status: ground
    source: nbs-m40
    where: Table 11, density at 20 °C, column 30 weight percent rhodium
  - benchmark: melting_point
    label: Melting range of Pt-10Rh
    value: 1840
    value_high: 1870
    bound: range
    unit: °C
    scope: material
    conditions:
      composition: Pt-10%Rh
      product_form: not stated
    method: Melting range printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh10
    where: General information table, Melting Range row
  - benchmark: melting_point
    label: Melting range of Pt-30Rh
    value: 1920
    value_high: 1925
    bound: range
    unit: °C
    scope: material
    conditions:
      composition: Pt-30%Rh
      product_form: wire
    method: Melting range printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh30
    where: General information table, Melting Range row
  - benchmark: elastic_modulus
    label: Young's modulus of Pt-10Rh
    value: 208
    unit: GPa
    scope: material
    conditions:
      composition: Pt-10%Rh
      temperature: not stated
    method: Value printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh10
    where: Mechanical properties table, Young's Modulus row
  - benchmark: elastic_modulus
    label: Young's modulus of Pt-30Rh
    value: 276
    unit: GPa
    scope: material
    conditions:
      composition: Pt-30%Rh
      temperature: not stated
    method: Value printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh30
    where: Mechanical properties table, Young's Modulus row
  - benchmark: shear_modulus
    label: Modulus of rigidity of Pt-10Rh
    value: 72
    unit: GPa
    scope: material
    conditions:
      composition: Pt-10%Rh
      temperature: not stated
    method: Value printed in the Heraeus datasheet under the name Modulus of Rigidity
    status: ground
    source: heraeus-ptrh10
    where: Mechanical properties table, Modulus of Rigidity row
  - benchmark: shear_modulus
    label: Modulus of rigidity of Pt-30Rh
    value: 95
    unit: GPa
    scope: material
    conditions:
      composition: Pt-30%Rh
      temperature: not stated
    method: Value printed in the Heraeus datasheet under the name Modulus of Rigidity
    status: ground
    source: heraeus-ptrh30
    where: Mechanical properties table, Modulus of Rigidity row
  - benchmark: yield_strength
    label: Yield strength of Pt-10Rh (range)
    value: 180
    value_high: 670
    bound: range
    unit: MPa
    scope: material
    conditions:
      composition: Pt-10%Rh
      temper_or_form: not stated; the datasheet gives one range for all product forms
    method: Range printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh10
    where: Mechanical properties table, Yield Strength row
  - benchmark: yield_strength
    label: Yield strength of Pt-30Rh (range)
    value: 200
    value_high: 950
    bound: range
    unit: MPa
    scope: material
    conditions:
      composition: Pt-30%Rh
      temper_or_form: not stated; the datasheet gives one range for all product forms
    method: Range printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh30
    where: Mechanical properties table, Yield Strength row
  - benchmark: ultimate_tensile_strength
    label: Tensile strength of Pt-10Rh (range)
    value: 300
    value_high: 680
    bound: range
    unit: MPa
    scope: material
    conditions:
      composition: Pt-10%Rh
      temper_or_form: not stated; the datasheet gives one range for all product forms
    method: Range printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh10
    where: Mechanical properties table, Tensile Strength row
  - benchmark: ultimate_tensile_strength
    label: Tensile strength of Pt-30Rh (range)
    value: 500
    value_high: 1000
    bound: range
    unit: MPa
    scope: material
    conditions:
      composition: Pt-30%Rh
      temper_or_form: not stated; the datasheet gives one range for all product forms
    method: Range printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh30
    where: Mechanical properties table, Tensile Strength row
  - benchmark: elongation
    label: Elongation of Pt-10Rh (range)
    value: 1.5
    value_high: 32
    bound: range
    unit: '%'
    scope: material
    conditions:
      composition: Pt-10%Rh
      temper_or_form: not stated
    method: Range printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh10
    where: Mechanical properties table, Elongation row
  - benchmark: elongation
    label: Elongation of Pt-30Rh (lower limit)
    value: 25
    bound: lower
    unit: '%'
    scope: material
    conditions:
      composition: Pt-30%Rh
      temper_or_form: not stated
    method: Lower limit printed as greater than 25 in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh30
    where: Mechanical properties table, Elongation row
  - benchmark: hardness_hv
    label: Vickers hardness of Pt-10Rh (range)
    value: 102
    value_high: 204
    bound: range
    unit: HV
    scope: material
    conditions:
      composition: Pt-10%Rh
      temper_or_form: not stated
    method: Range printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh10
    where: Mechanical properties table, Hardness row
  - benchmark: hardness_hv
    label: Vickers hardness of Pt-30Rh (range)
    value: 150
    value_high: 300
    bound: range
    unit: HV
    scope: material
    conditions:
      composition: Pt-30%Rh
      temper_or_form: not stated
    method: Range printed in the Heraeus datasheet
    status: ground
    source: heraeus-ptrh30
    where: Mechanical properties table, Hardness row
  - benchmark: emf_drift
    label: EMF drift of an 87Pt13Rh against Pt couple in air over 10,000 h
    value: -5
    unit: K
    scope: material
    conditions:
      couple: 87Pt13Rh/Pt, 0.5 mm wire
      temperature: 1500 to 1600 K
      atmosphere: air
      duration: 10,000 h
      sign: negative value means lower emf
    method: Maximum drift of the pairs reported by NASA Lewis; the authors give it in kelvin of temperature-equivalent emf change
    status: ground
    source: glawe-nasa
    where: Abstract, and Conclusion 6
  - benchmark: emf_drift
    label: EMF drift of an 87Pt13Rh against Pt couple in argon over 10,000 h
    value: -22
    unit: K
    scope: material
    conditions:
      couple: 87Pt13Rh/Pt, 0.5 mm wire
      temperature: 1500 to 1600 K
      atmosphere: argon
      duration: 10,000 h
      sign: negative value means lower emf
    method: Average total drift reported by NASA Lewis for the 0.5 mm pairs
    status: ground
    source: glawe-nasa
    where: Conclusion 1
corrosion:
  - environment: Air at 1500 to 1600 K for 10,000 h (87Pt13Rh against Pt couples)
    headline: 'In air the Pt-13Rh couple drifted least of the three atmospheres tested: about 5 K in 10,000 h.'
    effect: Glawe and Szaniszlo report a maximum drift of -5 K (lower emf) for 87Pt13Rh/Pt pairs in air over 10,000 h. They say impurities picked up from the insulators are converted to harmless oxides in air, so the drift is very low.
    rating: low
    conditions:
      atmosphere: air
      temperature: 1500 to 1600 K
      duration: 10,000 h
      insulators: high-purity alumina
    source: glawe-nasa
    where: Abstract; Conclusions 4 and 6
  - environment: Argon at 1500 to 1600 K for 10,000 h (0.5 mm 87Pt13Rh against Pt)
    headline: In argon the same couple drifted about 22 K in 10,000 h, more than four times the air value.
    effect: The drift in argon increased after the first few thousand hours. The authors say the drift is probably caused by insulator impurities that contaminate the wire, and that the smaller 0.33 mm wire drifted about twice as much as the 0.5 mm wire.
    rating: moderate
    conditions:
      atmosphere: argon
      temperature: 1500 to 1600 K
      duration: 10,000 h
    source: glawe-nasa
    where: Conclusions 1 and 4
  - environment: Reducing atmosphere at high temperature, with silicon from refractories
    headline: Platinum and its rhodium alloys deteriorate in reducing gases at high temperature, and silicon speeds the damage.
    effect: NBS Monograph 40 says platinum and its rhodium alloys deteriorate under reducing conditions at high temperatures by absorbing gases and metals reduced from the oxides of insulating refractories. It cites McQuillan, who found that platinum in the presence of silicon failed in less than an hour. Carbon and sulfur-bearing gases are named as common reducing atmospheres.
    rating: severe
    conditions:
      atmosphere: reducing, containing carbon or sulfur gases
      temperature: high
      contaminant: silicon from refractories
    source: nbs-m40
    where: Section on chemical behaviour of platinum and its alloys, paragraph on reducing conditions
  - environment: Aqua regia (mixed strong acid)
    headline: The source says Pt-Rh alloys resist aqua regia only above about 20 wt% rhodium, so the 10 and 13 wt% alloys are not covered.
    effect: NBS Monograph 40 says platinum is dissolved by aqua regia. The platinum-rhodium alloys are said to be unaffected by aqua regia when they contain more than about 20 percent rhodium. The Pt-30Rh alloy meets that limit; the 10 and 13 wt% alloys are below it, and the source gives no rating for them.
    rating: unknown
    conditions:
      environment: aqua regia
      threshold: more than about 20 percent rhodium
    source: nbs-m40
    where: Section on chemical behaviour of platinum and its alloys, paragraph on aqua regia
risks:
  hazards:
    - text: PubChem's record for rhodium metal, the main metal in the alloy, says the substance does not meet GHS hazard criteria in 81.3% (239 of 294) of company reports. The record gives a flammable-solid classification (H228) in 15.3% of reports. The record is for the pure metal, not for the alloy, so check the supplier's safety data sheet for the wire or powder you handle.
      ghs:
        - 'H228 (15.3% of reports): Flammable solid'
      source: pubchem-rh
      where: GHS Classification section (CID 23948)
  failure_risks:
    - mode: Grain growth and loss of mechanical stability in the pure platinum leg
      trigger: Use above about 1200 °C
      consequence: Edler et al. say pure platinum grows grains quickly at high temperature, which weakens the thermoelement mechanically; above about 1200 °C the drift also rises, mainly from thermoelectric inhomogeneity.
      severity: high
      source: edler-springer
      where: Introduction, second page
    - mode: Silicon contamination of the platinum leg in a reducing atmosphere
      trigger: Reducing gases at high temperature with silicon from refractories
      consequence: NBS Monograph 40 cites a result in which platinum with silicon failed in less than an hour in a reducing atmosphere.
      severity: high
      source: nbs-m40
      where: Section on chemical behaviour, paragraph on reducing conditions
    - mode: Long-term emf drift in argon or vacuum
      trigger: 10,000 h at 1500 to 1600 K in argon; in one vacuum system, most noble-metal couples failed within a few thousand hours
      consequence: About 22 K of drift in argon for 0.5 mm 87Pt13Rh/Pt pairs. In one vacuum test system, most noble-metal couples failed by open circuit within a few thousand hours.
      severity: moderate
      source: glawe-nasa
      where: Abstract; Conclusion 1
  side_effects:
    - text: Impurities from the insulators, mainly iron and silicon, were picked up by the noble-metal wires. The authors say they appeared in about equal amounts in the noble and refractory wires.
      affects: Emf of the couple (drift)
      source: glawe-nasa
      where: Conclusion 8
    - text: The noble-metal wire showed large grain growth after 10,000 h of exposure, while the tungsten-rhenium wire showed negligible growth.
      affects: Mechanical strength of the thermoelement
      source: glawe-nasa
      where: Conclusion 7
  handling:
    - text: NBS Monograph 40 says these thermocouples should be used under oxidizing or neutral conditions.
      source: nbs-m40
      where: Section on chemical behaviour, paragraph on reducing conditions
    - text: Keep the junction away from silicon-bearing refractories and from reducing gases at high temperature.
      source: nbs-m40
      where: Section on chemical behaviour, paragraph on reducing conditions
  mitigations:
    - text: Recalibrate regularly. Edler et al. say the drift above about 1200 °C requires regular calibration, especially where accuracy matters most.
      source: edler-springer
      where: Introduction, second page
uses:
  - application: thermal-control
    device: Type S thermocouples (Pt-10Rh against Pt)
    example: NIST's ITS-90 reference table gives 9.587 mV at 1000 °C for a Type S couple, against a 0 °C reference junction. The standard range printed for Type S is -50 to 1768 °C.
    source: nist-m175
    where: Table B4.1.1, row 1000; Table 1.1.1, row S
  - application: thermal-control
    device: Type R thermocouples (Pt-13Rh against Pt)
    example: NIST's reference table gives 10.506 mV at 1000 °C for a Type R couple, against a 0 °C reference junction. The standard range printed for Type R is -50 to 1768 °C.
    source: nist-m175
    where: Table B3.1.1, row 1000; Table 1.1.1, row R
  - application: thermal-control
    device: Thermocouples, heating elements and resistance thermometers made from Pt-30Rh wire
    example: Heraeus lists the applications of its PtRh30 wire as thermocouples, heating elements, resistance thermometers and anemometers.
    source: heraeus-ptrh30
    where: General information table, Applications row
supply:
  - subject: Platinum (world mine production, 2025e, platinum-group metals chapter)
    abundance: USGS reports world platinum mine production of 170,000 kg in 2025e, rounded. US net import reliance was 89% of apparent consumption in 2025e.
    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 2025 List of Critical Minerals (platinum listed; the page names it among uses for aerospace alloys and chemical refining)
        listed: true
      - list: EU critical raw materials list (2023 fifth list, shown on the Commission page as platinum group metals)
        listed: true
    recycling: 'USGS: about 140,000 kg of palladium and platinum were recovered globally from new and old scrap in 2025, including 8,600 kg of platinum recovered from automobile catalytic converters in the United States.'
    substitutes:
      - 'USGS: for some industrial end uses, one platinum-group metal can substitute for another, but with losses in efficiency.'
    source: usgs-mcs2026-pgm
    where: World Mine Production and Reserves table (platinum 2025e; shares calculated by Space Mushroom from the kilogram values against the printed world total of 170,000 kg); Recycling; Substitutes
  - subject: Rhodium
    abundance: USGS gives the 2025e rhodium price at 5,800 dollars per troy ounce (up 24% on 2024, per the chapter's text) and US rhodium imports at 14,000 kg in 2025e.
    producers: []
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (rhodium listed; the page names it among uses in catalytic converters and electrical components)
        listed: true
      - list: EU critical raw materials list (2023 fifth list, platinum group metals)
        listed: true
    recycling: USGS gives recycling figures for palladium and platinum only in the 2026 chapter read here.
    substitutes:
      - 'USGS: one platinum-group metal can substitute for another for some industrial end uses, with losses in efficiency.'
    source: usgs-mcs2026-pgm
    where: Salient Statistics table (rhodium imports and price 2025e); Events, Trends and Issues paragraph; no rhodium mine-production table is printed in this chapter, so no country shares are given
documents:
  - title: Heraeus Precious Metals datasheet PtRh10 (Pt-10%Rh), document 01, status 09/2021
    type: datasheet
    url: https://pim.heraeus.com/datasheets/HPM/FM/Glass%20Manufacturing%20Materials/PtRh10_Datasheet_EN_(Heraeus_Precious_Metals).pdf
    year: 2021
  - title: Heraeus Precious Metals datasheet PtRh30 (Pt-30%Rh), document 01, status 09/2021
    type: datasheet
    url: https://pim.heraeus.com/datasheets/HPM/FM/Glass%20Manufacturing%20Materials/PtRh30_Datasheet_EN_(Heraeus_Precious_Metals).pdf
    year: 2021
  - title: 'NIST Monograph 175: Temperature-Electromotive Force Reference Functions and Tables for the Letter-Designated Thermocouple Types Based on the ITS-90'
    type: report
    url: https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nistmonograph175.pdf
    year: 1993
  - title: 'NBS Monograph 40: Thermocouple Materials (Fourth Symposium on Temperature, 1961)'
    type: report
    url: https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nbsmonograph40.pdf
    year: 1962
  - title: Long-Term Drift of Some Noble- and Refractory-Metal Thermocouples, 1500 to 1600 K in Air, Argon, and Vacuum (NASA Lewis)
    type: report
    url: https://ntrs.nasa.gov/citations/19710015775
    year: 1971
  - title: 'Pt-40%Rh versus Pt-6%Rh Thermocouples: an emf-temperature reference function, Int. J. Thermophysics 42, 150 (open access; read as the NPL eprint copy)'
    type: paper
    url: https://link.springer.com/article/10.1007/s10765-021-02895-w
    year: 2021
  - title: Thermo Scientific catalogue, Platinum 13 wt% Rhodium wire, product 013018.BY
    type: datasheet
    url: https://www.thermofisher.com/order/catalog/product/013018.BY
    year: 2026
  - title: PubChem compound record, Rhodium (CID 23948), GHS classification
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Rhodium
    year: 2026
  - title: USGS Mineral Commodity Summaries 2026, Platinum-Group Metals (February 2026)
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-platinum-group.pdf
    year: 2026
gaps:
  - No melting point for the Pt-13Rh alloy was found in the pages checked. The Type R alloy therefore has density but no melting value here.
  - The Pt-13Rh density (19.595 g/cm3) comes from one supplier catalogue listing and was not checked against a second source.
  - Heraeus datasheets cover Pt-10Rh and Pt-30Rh only. No mechanical, thermal-conductivity or specific-heat datasheet value for Pt-13Rh was found.
  - No thermal conductivity, specific heat or coefficient of thermal expansion for the Pt-10Rh and Pt-30Rh alloys was found in the pages checked.
  - No UNS, EN, ASTM or other designation for the thermocouple alloys was printed in the pages checked; the standard for thermocouple wire (IEC 60584 or ASTM E230) was not opened.
  - The USGS 2026 PGM chapter prints mine production for platinum and palladium only. Rhodium mine production by country, and so rhodium supply shares, were not found in the pages checked.
  - The Matthey article on rhodium migration in platinum-rhodium thermocouples returned HTTP 403 and was not checked. The rhodium-vapour drift mechanism is therefore given only as the NBS and Edler statements.
  - Hazard data rest on the PubChem rhodium record. The alloy's own safety data sheet was not found, and the Heraeus datasheets give no hazard data.
  - Glass-fibre bushing operating data (1800 to 2500 °F) come from a US patent (US 4014692) seen only as a search snippet. No value from it is used in this profile.
  - Space flight use of platinum-rhodium thermocouples on the Shuttle Orbiter is documented in the platinum profile (CAIB report) but was not checked here, so it is not cited.
  - Type B thermoelectric voltage at 1000 °C was not found in the pages checked. The thermoelectric_emf and thermocouple_range benchmark names are not in the canonical property file; they are short snake_case names, and emf_drift is also not canonical.
sources:
  heraeus-ptrh10:
    title: PtRh10 (Pt-10%Rh) datasheet, Heraeus Precious Metals
    id: Heraeus document 01, status 09/2021
    url: https://pim.heraeus.com/datasheets/HPM/FM/Glass%20Manufacturing%20Materials/PtRh10_Datasheet_EN_(Heraeus_Precious_Metals).pdf
    year: 2021
    kind: datasheet
    license: manufacturer datasheet, cited not reproduced
  heraeus-ptrh30:
    title: PtRh30 (Pt-30%Rh) datasheet, Heraeus Precious Metals
    id: Heraeus document 01, status 09/2021
    url: https://pim.heraeus.com/datasheets/HPM/FM/Glass%20Manufacturing%20Materials/PtRh30_Datasheet_EN_(Heraeus_Precious_Metals).pdf
    year: 2021
    kind: datasheet
    license: manufacturer datasheet, cited not reproduced
  nist-m175:
    title: 'NIST Monograph 175: Temperature-Electromotive Force Reference Functions and Tables for the Letter-Designated Thermocouple Types Based on the ITS-90'
    id: NIST Monograph 175, Burns, Scroger, Strouse, Croarkin and Guthrie
    url: https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nistmonograph175.pdf
    year: 1993
    kind: report
    license: public domain (NIST)
  nbs-m40:
    title: 'NBS Monograph 40: Thermocouple Materials'
    id: NBS Monograph 40 (Fourth Symposium on Temperature, 1961)
    url: https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nbsmonograph40.pdf
    year: 1962
    kind: report
    license: public domain (NIST)
  glawe-nasa:
    title: Long-Term Drift of Some Noble- and Refractory-Metal Thermocouples, 1500 to 1600 K in Air, Argon, and Vacuum
    id: NASA NTRS 19710015775; G. E. Glawe and A. J. Szaniszlo, NASA Lewis Research Center (year taken from the NTRS record; the scanned text does not print it clearly)
    url: https://ntrs.nasa.gov/citations/19710015775
    year: 1971
    kind: report
    license: public domain (NASA)
  edler-springer:
    title: 'Pt-40%Rh versus Pt-6%Rh Thermocouples: An emf-Temperature Reference Function for the Temperature Range 0 °C to 1769 °C'
    id: doi:10.1007/s10765-021-02895-w (Int. J. Thermophys. 42, 150)
    url: https://link.springer.com/article/10.1007/s10765-021-02895-w
    year: 2021
    kind: paper
    license: CC BY 4.0
  thermo-pt13rh:
    title: Platinum 13 wt% Rhodium wire, Thermo Scientific Chemicals, catalogue product 013018.BY
    id: Thermo Fisher product 013018.BY
    url: https://www.thermofisher.com/order/catalog/product/013018.BY
    year: 2026
    kind: web
    license: supplier catalogue, cited not reproduced
  pubchem-rh:
    title: PubChem compound record, Rhodium (CID 23948)
    id: CID 23948; CAS 7440-16-6
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Rhodium
    year: 2026
    kind: database
    license: public domain (NCBI)
  usgs-mcs2026-pgm:
    title: Mineral Commodity Summaries 2026, Platinum-Group Metals
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-platinum-group.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-crit2025:
    title: About the 2025 List of Critical Minerals (USGS, final list of 60 minerals)
    id: Final 2025 List of Critical Minerals, November 2025
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
    kind: web
    license: public domain (USGS)
  ec-crm:
    title: Critical raw materials (European Commission; list of critical raw materials, 2023 fifth list)
    id: EU critical raw materials list
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    year: 2023
    kind: web
    license: European Commission web page
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 24
  unreachable: 2
  caveats: 4
  note: 'Values were read by an AI assistant on 2026-10-26 from the pages and PDFs named in each entry. Unreachable: the Matthey rhodium-migration article (HTTP 403) and the Pt-13Rh melting point (no page read). Caveats: the 13 wt% density rests on one catalogue listing; the Heraeus strength and hardness figures are ranges without a stated temper; NBS Table 11 densities come from a 1960s table; the supply shares are calculated from kilogram values.'
story:
  recipe:
    line: Platinum-rhodium alloys are platinum with 10, 13 or 30 wt% rhodium. The three grades in this profile are Pt-10 wt% Rh (Type S), Pt-13 wt% Rh (Type R) and Pt-30 wt% Rh (Type B, against a Pt-6 wt% Rh leg), as NIST Monograph 175 and Heraeus name them.
    parts:
      - name: Platinum
        symbol: Pt
        share: 90 wt% in Pt-10Rh, 87 wt% in Pt-13Rh, 70 wt% in Pt-30Rh
        role: The matrix of each alloy. In each couple the platinum-rhodium leg is the positive leg and the pure platinum leg is the negative one (NBS Monograph 40).
      - name: Rhodium
        symbol: Rh
        share: 10 wt% in Pt-10Rh, 13 wt% in Pt-13Rh, 30 wt% in Pt-30Rh
        role: The alloying element. Its share defines each thermocouple type (NIST Monograph 175, Table 1.1.1).
  risk_groups:
    - title: For people
      level: 0
      verdict: Not classified in most company reports
      lead: The rhodium record in PubChem is the closest hazard data read for these alloys. The alloys are solid metals, but the powder form can be flammable.
      points:
        - label: The wire
          line: PubChem reports that rhodium metal does not meet GHS hazard criteria in 81.3% (239 of 294) of company reports. Its GHS summary lists H228 (flammable solid) for 15.3% of reports.
        - label: Dust and swarf
          line: PubChem does not say which physical form the H228 reports refer to. Check the supplier safety data sheet for the form you handle.
        - label: Datasheets
          line: The Heraeus datasheets give no hazard or toxicity statement for either alloy.
    - title: In service
      lead: These points come from laboratory and test-rig results, not from field incidents.
      points:
        - label: Reducing gases
          line: NBS Monograph 40 says platinum and its rhodium alloys deteriorate under reducing conditions at high temperature, by absorbing gases and metals reduced from insulator oxides.
        - label: Silicon
          line: Silicon from refractories is a contaminant that worsens the damage. A result cited in NBS Monograph 40 found platinum with silicon failed in less than an hour in a reducing atmosphere.
        - label: Drift
          line: In NASA's 10,000 h tests at 1500 to 1600 K, an 87Pt13Rh against Pt couple drifted about 5 K in air and about 22 K in argon. In one vacuum test system most noble-metal couples failed by open circuit within a few thousand hours.
        - label: Above 1200 °C
          line: Edler et al. say pure platinum grows grains quickly above about 1200 °C, and that drift rises there mainly from thermoelectric inhomogeneity. Regular calibration is needed.
    - title: Handling and storage
      points:
        - label: Atmosphere
          line: NBS Monograph 40 says these thermocouples should be used under oxidizing or neutral conditions.
        - label: Contact
          line: Keep the junction away from silicon-bearing refractories and from carbon or sulfur-bearing reducing gases at high temperature.
  why: 'Platinum-rhodium alloys are the thermoelements used for the standard high-temperature noble-metal thermocouples. The rhodium content defines each type: Type S uses 10 wt% rhodium, Type R 13 wt% and Type B 30 wt%. Each has a standardised range in NIST Monograph 175. NASA''s drift tests show small drift in air. Heraeus lists melting ranges of 1840 to 1870 °C for Pt-10Rh and 1920 to 1925 °C for Pt-30Rh, well above the calibration ranges. Heraeus also lists glass-fibre bushings as an application of the Pt-10Rh alloy.'
  uses:
    - where: Temperature sensing in thermocouples
      line: NIST Monograph 175 defines Type S (Pt-10Rh against Pt), Type R (Pt-13Rh against Pt) and Type B (Pt-30Rh against Pt-6Rh) as standard couples. The Heraeus PtRh30 datasheet lists thermocouples, heating elements, resistance thermometers and anemometers as its uses.
    - where: Glass-fibre bushings
      line: The Heraeus datasheet for PtRh10 lists glass manufacturing, drain bushings and glass-fibre bushings as applications. This use is terrestrial; no space application for the alloys was found in the sources checked.
    - where: Heating elements and resistance thermometers
      line: The Heraeus datasheet for PtRh30 lists its product form as wire, and it names heating elements and resistance thermometers among its applications.
  can_do:
    - label: Upper temperature
      benchmark: thermocouple_range
      value: '-50 to 1768 °C (Types R and S), 0 to 1820 °C (Type B)'
      line: These are the calibration ranges printed in NIST Monograph 175. Edler et al. describe the same alloys as usable at very high temperatures, with drift rising above about 1200 °C.
    - label: Thermoelectric output
      benchmark: thermoelectric_emf
      value: 9.587 mV (Type S) and 10.506 mV (Type R) at 1000 °C
      line: Both are referred to a 0 °C reference junction on the ITS-90 scale, from NIST's reference tables. The printed values are for the complete couples, not for one alloy alone.
    - label: Stability
      benchmark: emf_drift
      value: '-5 K in air, -22 K in argon (10,000 h, 1500 to 1600 K)'
      line: NASA's long-term test shows that air keeps the 87Pt13Rh couple most stable. The authors say impurities from insulators are converted to harmless oxides in air.
    - label: Melting point
      benchmark: melting_point
      value: 1840 to 1870 °C (Pt-10Rh); 1920 to 1925 °C (Pt-30Rh)
      line: Heraeus prints these melting ranges. The Pt-13Rh alloy's melting point was not found in the pages checked.
  compare: 'Across the grades, density falls as rhodium rises: 19.97 g/cm3 at 10 wt% and 17.6 g/cm3 at 30 wt% in NBS Table 11. The 30 wt% alloy has the highest melting range (1920 to 1925 °C) and the higher tensile range (500 to 1000 MPa) of the two Heraeus grades. The table rows compare density, melting range and tensile strength. They come from different manufacturers and tests, so read them as handbook and datasheet figures, not as one test series.'
  compare_rows:
    - label: Density at 20 °C
      benchmark: density
    - label: Melting range
      benchmark: melting_point
    - label: Tensile strength
      benchmark: ultimate_tensile_strength
  handling:
    - Use these couples under oxidizing or neutral conditions. Reducing gases at high temperature damage them.
    - Keep silicon-bearing refractories and carbon or sulfur-bearing reducing gases away from the junction.
    - Recalibrate regularly, especially above about 1200 °C.
    - Check the supplier safety data sheet for powder or swarf, which the rhodium record marks as flammable in some reports.
  good_for:
    - Thermocouples for high temperature in oxidizing or neutral air. NIST sets the standard ranges at -50 to 1768 °C for Types R and S and 0 to 1820 °C for Type B.
    - Long-term stable emf in air. NASA measured about 5 K of drift in 10,000 h for an 87Pt13Rh against Pt couple.
    - Glass-fibre bushings. The Heraeus PtRh10 datasheet lists glass-fibre bushings as an application.
  watch_out:
    - Reducing gases and silicon from refractories. NBS Monograph 40 says these attack platinum and its rhodium alloys.
    - Grain growth and drift above about 1200 °C (Edler et al. 2021).
    - Cost and supply. USGS gives the 2025e rhodium price at 5,800 dollars per troy ounce, and most platinum mine output comes from South Africa (70.6% calculated).
  verdict: Platinum-rhodium alloys are the reference thermoelements for the highest standard temperatures. Their emf is well documented in NIST's tables and their drift in air is small in NASA's tests. Keep them in oxidizing or neutral atmospheres, and avoid silicon and reducing gases. Gaps remain for Pt-13Rh melting point, thermal conductivity and the alloy's own safety data.