spore: profile
id: palladium
spore_version: 0.2
family: precious-metals
name: Palladium
abbreviation: Pd
role: catalyst, electrical-contact and hydrogen-handling metal
category: metals
type: precious-metals
summary: |
  Palladium is a dense, soft, silver-white platinum-group metal. Reference data list a density of 12.02 g/cm3 and a melting point of 1554.9 degC, and a supplier datasheet gives an annealed tensile strength of 280 MPa. Its most distinctive trait is that it soaks up hydrogen: at 25 degC and 1 bar the hydrogen-rich beta phase holds about 0.7 hydrogen atoms per palladium atom, and the lattice swells by more than 10% when it forms. The USGS lists its uses as catalytic converters, chemical and refinery catalysts, and electronics such as multilayer ceramic capacitors. A NASA-sponsored 1969 device used a palladium-silver alloy to strip dissolved hydrogen from fuel-cell water.
best_for: Catalysis and selective hydrogen passage (a 75% palladium-25% silver alloy dropped dissolved hydrogen from 60 psia to under 0.5 psia in a NASA-sponsored separator)
weakest_at: 'Hydrogen embrittlement: pure palladium membranes warp and fracture when the alpha-to-beta hydride transition expands the lattice by more than 10%, and supply is concentrated in two countries'
identity:
  formula: Pd
  cas: 7440-05-3
  crystal_system: face-centred cubic
  source: pubchem-pd
  where: Record "Palladium" (CID 23938), Names and Identifiers (molecular formula Pd; CAS 7440-05-3 in the ECHA registration link); face-centred cubic structure with a = 3.891 angstrom from the Goodfellow General Properties table
tags:
  environments:
    - low-earth-orbit
  stresses: []
  applications:
    - electronics-and-chips
    - propulsion-and-tanks
    - cryogenic-fuel
properties:
  - benchmark: density
    label: Density of palladium metal
    value: 12.02
    unit: g/cm3
    scope: material
    conditions:
      form: bulk metal, purity not stated
      temperature: not stated for this entry
    method: Handbook value listed in PubChem from the Hazardous Substances Data Bank, which cites Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed., vol. 19, p. 350 (1996)
    status: ground
    note: Other sources agree. Goodfellow lists 12.02 g/cm3 at 20 degC, Deringer-Ney lists 12.02 g/cm3, and WebElements lists 12023 kg/m3 for the solid.
    source: pubchem-pd
    where: Chemical and Physical Properties > Experimental Properties > Density (first entry)
  - benchmark: melting_point
    label: Melting point
    value: 1554.9
    unit: degC
    scope: material
    conditions:
      pressure: not stated
      form: pure metal
    method: Handbook value listed in PubChem, citing Lide (ed.), CRC Handbook of Chemistry and Physics, 81st ed., 2000, p. 4-77
    status: ground
    note: PubChem also lists 1554.8 degC from another entry. Deringer-Ney gives a melting temperature of 1552 degC for its palladium and Goodfellow gives 1,554.9 degC (1,828.0 K).
    source: pubchem-pd
    where: Chemical and Physical Properties > Experimental Properties > Melting Point
  - benchmark: boiling_point
    label: Boiling point
    value: 2963
    unit: degC
    scope: material
    conditions:
      pressure: 760 mm Hg (the second PubChem entry states this)
    method: Handbook value listed in PubChem, citing Lide (ed.), CRC Handbook of Chemistry and Physics, 81st ed., 2000, p. 4-77
    status: ground
    source: pubchem-pd
    where: Chemical and Physical Properties > Experimental Properties > Boiling Point
  - benchmark: thermal_conductivity
    label: Thermal conductivity
    value: 72
    unit: W/(m.K)
    scope: material
    conditions:
      form: pure metal
      temperature: not stated on the page
    method: Value listed in the WebElements physical-properties table
    status: ground
    note: Goodfellow lists 71.8 W/m.K and Deringer-Ney lists 70 W/m-K (40 Btu/hr-ft-degF), so the three sources agree within about 3%.
    source: webelements-pd
    where: Physical properties table, thermal conductivity
  - benchmark: electrical_resistivity
    label: Electrical resistivity
    value: 10.8
    unit: uOhm.cm
    scope: material
    conditions:
      form: temper-independent value in the supplier table
      standard_referenced: ASTM B 589-94 (Refined Palladium)
    method: Value in the supplier's table of properties that do not depend on temper
    status: ground
    note: The Deringer-Ney table gives 64.8 uOhm-in alongside 10.8 uOhm-cm. WebElements lists 10.8 x 10^-8 Ohm m (the same value) and Goodfellow lists 105 nOhm.m at 20 degC.
    source: deringer-ney-pd
    where: Constant properties table, Electrical Resistivity
  - benchmark: electrical_conductivity_iacs
    label: Electrical conductivity
    value: 16
    unit: '% IACS'
    scope: material
    conditions:
      form: palladium as supplied by Deringer-Ney
      reference: International Annealed Copper Standard
    method: Value in the supplier's table of properties that do not depend on temper
    status: ground
    source: deringer-ney-pd
    where: Constant properties table, Electrical Conductivity
  - benchmark: cte
    label: Coefficient of linear thermal expansion
    value: 11.8
    unit: ppm/K
    scope: material
    conditions:
      form: pure metal
      temperature: not stated on the page
    method: Value listed in the WebElements physical-properties table as 11.8 x 10^-6 per kelvin
    status: ground
    note: Deringer-Ney lists 1.2E-05 per kelvin (6.5E-06 per degF).
    source: webelements-pd
    where: Physical properties table, coefficient of linear thermal expansion
  - benchmark: elastic_modulus
    label: Young's modulus
    value: 121
    unit: GPa
    scope: material
    conditions:
      form: pure metal
      temperature: not stated on the page
    method: Value listed in the WebElements physical-properties table
    status: ground
    note: Goodfellow also lists 121 GPa. Deringer-Ney lists an elastic modulus of 117 GPa (17.0 Msi) and a shear modulus of 44.0 GPa.
    source: webelements-pd
    where: Physical properties table, Young's modulus
  - benchmark: poissons_ratio
    label: Poisson's ratio
    value: 0.39
    unit: dimensionless
    scope: material
    conditions:
      form: palladium as supplied by Deringer-Ney
    method: Value in the supplier's constant-properties table
    status: ground
    note: WebElements and Goodfellow also list 0.39.
    source: deringer-ney-pd
    where: Second constant-properties table, Poisson's Ratio
  - benchmark: tensile_strength_annealed
    label: Ultimate tensile strength, annealed
    value: 280
    unit: MPa
    scope: material
    conditions:
      temper: annealed
      standard_referenced: ASTM B 589-94 (Refined Palladium)
      test_standard: not stated on the page
    method: Value in the supplier's annealed-temper tensile table (41 ksi)
    status: ground
    note: Goodfellow lists a lower, wider range of 170-210 MPa for tensile strength and 60-120 MPa for yield strength, with no temper stated. The two suppliers disagree, so treat annealed strength as supplier-dependent.
    source: deringer-ney-pd
    where: Annealed Temper, tensile properties table
  - benchmark: yield_strength_annealed
    label: 0.2% offset yield strength, annealed
    value: 270
    unit: MPa
    scope: material
    conditions:
      temper: annealed
      offset: 0.2%
    method: Value in the supplier's annealed-temper tensile table (39 ksi)
    status: ground
    note: This is close to the tensile strength of 280 MPa, which is unusual for an annealed metal; Goodfellow's 60-120 MPa yield range is far lower. We could not resolve the difference from the pages alone.
    source: deringer-ney-pd
    where: Annealed Temper, tensile properties table
  - benchmark: elongation_annealed
    label: Elongation to failure, annealed
    value: 25
    unit: '%'
    scope: material
    conditions:
      temper: annealed
      gauge_length: not stated
    method: Value in the supplier's annealed-temper tensile table
    status: ground
    note: Goodfellow lists 30-40% elongation at break.
    source: deringer-ney-pd
    where: Annealed Temper, tensile properties table
  - benchmark: vickers_hardness
    label: Vickers microhardness, annealed
    value: 40
    unit: HV
    scope: material
    conditions:
      temper: annealed
      load: not stated on the page
    method: Value in the supplier's annealed-temper hardness table (Knoop microhardness is 50 HK in the same table)
    status: ground
    note: Goodfellow lists about 55 HV for annealed palladium.
    source: deringer-ney-pd
    where: Annealed Temper, hardness table
  - benchmark: contact_resistance
    label: Contact resistance at 30 gf
    value: 6
    unit: mOhm
    scope: material
    conditions:
      contact_force: 30 gf
      state: as listed by the supplier; the oxidised case (1,000 h at 150 degC) also reads 6 mOhm
    method: Supplier contact-resistance test (method details not stated on the page)
    status: ground
    note: After 720 h at 50 degC in flowers of sulfur the same table reads 10 mOhm.
    source: deringer-ney-pd
    where: Second constant-properties table, Contact resistance rows
  - benchmark: lattice_parameter
    label: Lattice parameter (face-centred cubic)
    value: 3.891
    unit: angstrom
    scope: material
    conditions:
      temperature: room temperature
      structure: FCC
    method: Value listed in the supplier's General Properties table
    status: ground
    note: Deringer-Ney lists 3.89 angstrom.
    source: goodfellow-pd
    where: General Properties table, Crystal Structure
  - benchmark: h_to_pd_ratio_beta
    label: Hydrogen-to-palladium atom ratio, beta (hydride) phase
    value: 0.7
    unit: H/Pd
    scope: material
    conditions:
      temperature: 25 degC
      hydrogen_pressure: 1 bar
      phase: beta
    method: Statement in the introduction of an open-access research paper on palladium membranes ("about 0.7")
    status: ground
    note: The same passage gives about 0.015 for the hydrogen-poor alpha phase under the same conditions. This is a literature statement in the paper, not a measurement made by its authors.
    source: ma2021-pd-membranes
    where: Introduction, Pd-H phase behaviour
  - benchmark: h_to_pd_ratio_alpha
    label: Hydrogen-to-palladium atom ratio, alpha phase
    value: 0.015
    unit: H/Pd
    scope: material
    conditions:
      temperature: 25 degC
      hydrogen_pressure: 1 bar
      phase: alpha
    method: Statement in the introduction of an open-access research paper on palladium membranes ("about 0.015")
    status: ground
    source: ma2021-pd-membranes
    where: Introduction, Pd-H phase behaviour
  - benchmark: hydride_critical_temp
    label: Temperature below which alpha and beta phases coexist
    value: 293
    unit: degC
    scope: material
    conditions:
      hydrogen_pressure: below 20 bar
      effect: beta phase nucleates and grows in the alpha phase
    method: Statement in the introduction of an open-access research paper on palladium membranes ("about 293 degC")
    status: ground
    note: The paper adds that pure Pd membranes are therefore often limited to operating temperatures above 300 degC.
    source: ma2021-pd-membranes
    where: Introduction, critical temperature and pressure
  - benchmark: hydride_volume_expansion
    label: Volume expansion in the alpha-to-beta transition
    value: 10
    unit: '% (stated as ''over 10%'')'
    scope: material
    conditions:
      transition: alpha to beta palladium hydride
      note: lower bound only; the paper gives no upper value
    method: Statement in the paper ("the expansion of volume for the phase transition is over 10%")
    status: ground
    note: The paper links this expansion to internal stress, warping and fracture of pure Pd membranes, and reports that 2 mm outer-diameter hollow fibre membranes less than 4 micrometres thick resisted embrittlement below 100 degC.
    source: ma2021-pd-membranes
    where: Introduction and Results on embrittlement
  - benchmark: dissolved_h2_pressure_out
    label: Dissolved-hydrogen partial pressure after a Pd-Ag separator
    value: 0.5
    unit: psia (stated as 'less than')
    scope: material
    conditions:
      inlet_partial_pressure: 60 psia
      water_temperature: 75 degF
      water_flow: 10 ml per minute
      membrane: 75% palladium-25% silver alloy tubes coated with palladium black, 18 tubes, 1/8 in outer diameter, 10 mil wall
    method: NASA Tech Brief describing a separator built by The Garrett Corporation under contract to the Manned Spacecraft Center
    status: ground
    note: The same brief reports a test unit ran more than 5 months (3700 hours) without loss of efficiency. The separator was devised to remove dissolved hydrogen from water produced by fuel cells with an alkaline electrolyte.
    source: nasa-tech-brief-1969
    where: Article text, paragraph on the fabricated separator
  - benchmark: pd_in_mobile_phone_pcb
    label: Palladium in printed circuit boards of mobile phones
    value: 119
    unit: ppm
    scope: material
    conditions:
      sample: printed circuit boards from 30 mobile phones
      method: boards milled, cryo-milled, leached with aqua regia, leachate analysed
      note: the study separates mobile phones from smartphones
    method: Published waste-electronics study (aqua regia leach, then solution analysis)
    status: ground
    note: Same abstract gives 20 ppm for 10 internet routers and 55 ppm for 30 smartphones, so the palladium level was lower in the newer smartphone boards.
    source: holgersson2018
    where: Abstract (precious-metal concentrations in PCBs)
  - benchmark: pd_in_smartphone_pcb
    label: Palladium in printed circuit boards of smartphones
    value: 55
    unit: ppm
    scope: material
    conditions:
      sample: printed circuit boards from 30 smartphones
      method: boards milled, cryo-milled, leached with aqua regia, leachate analysed
    method: Published waste-electronics study (aqua regia leach, then solution analysis)
    status: ground
    source: holgersson2018
    where: Abstract (precious-metal concentrations in PCBs)
corrosion:
  - environment: Acids, alkalis and organic solvents
    headline: Palladium dissolves in aqua regia and fused alkalies but not in organic acids.
    effect: PubChem, quoting Hawley's Condensed Chemical Dictionary, lists palladium as soluble in aqua regia and fused alkalies and insoluble in organic acids. A Merck Index entry quoted there says that at a red heat the metal converts to the monoxide. We did not find a corrosion-rate table.
    rating: unknown
    conditions:
      basis: handbook statements quoted in PubChem
      rates: none found
    source: pubchem-pd
    where: Experimental Properties > Solubility; Hazardous Reactivities and Incompatibilities
  - environment: Hydrogen gas
    headline: 'Not corrosion in the usual sense: hydrogen enters the lattice and can distort and crack pure palladium.'
    effect: Below about 293 degC and under 20 bar of hydrogen, the hydrogen-rich beta phase grows inside the hydrogen-poor alpha phase. The two share a crystal symmetry but differ in volume, and the expansion on transition is over 10%. Hydrogen embrittlement is reported to warp and destroy pure Pd membranes. NASA's permeation report notes that palladium is typically alloyed with silver to protect its strength and shape-holding against hydrogen.
    rating: severe
    conditions:
      temperature: below about 293 degC
      hydrogen_pressure: below 20 bar
      metal: pure palladium, not alloyed
    source: ma2021-pd-membranes
    where: Introduction and Results; NASA/TM-2019-220189 Introduction
risks:
  hazards:
    - text: 'PubChem aggregates 616 company reports to the ECHA inventory: 59.3% (365 reports) say the chemical does not meet GHS hazard criteria, and 31.5% classify it as a flammable solid (H228, signal word Danger). Because the reports disagree, the classification depends on the supplier and the form of the metal.'
      ghs:
        - H228
      source: pubchem-pd
      where: Safety and Hazards > Hazards Identification > GHS Classification
    - text: Palladium dust is combustible when exposed to heat or flame and can be a fire and explosive hazard. Finely divided palladium (palladium black) used as a hydrogenation catalyst is usually pyrophoric. A user report in PubChem describes palladium on carbon (10% wet) starting a small fire when added to a flask containing hydrogen and methanol.
      ghs: []
      source: pubchem-pd
      where: Hazards Summary; Fire Potential; Reactivity Alerts
    - text: Possible skin sensitiser. Contact dermatitis has been associated with metallic palladium, especially palladium alloys; occupational asthma has been reported but is very rare.
      ghs: []
      source: pubchem-pd
      where: Hazards Summary; Skin, Eye, and Respiratory Irritations
  failure_risks:
    - mode: Hydrogen embrittlement and warping of pure palladium
      trigger: Hydrogen absorption below about 293 degC and under 20 bar, which forms the beta hydride phase alongside the alpha phase
      consequence: The lattice swells by more than 10% where beta forms, so internal stress builds and pure Pd membranes warp and fracture.
      severity: high
      source: ma2021-pd-membranes
      where: Introduction and Results
    - mode: Loss of strength and shape-holding in hydrogen
      trigger: Exposure of thin pure palladium purification membranes to hydrogen
      consequence: NASA notes membranes are typically alloyed with silver to protect against hydrogen affecting the strength and shape-holding of the metal; the silver fraction can approach 60 percent, with 25 percent giving a good balance.
      severity: moderate
      source: smith2019-nasa-tm
      where: Introduction
  side_effects:
    - text: Palladium black on the surface of a separator tube was bonded by reducing applied palladium chloride in hydrogen, at nominal loadings of 2 milligrams per square centimetre of alloy surface. Tubes much larger than 1/8 in. would be less efficient and smaller ones could not be coated inside.
      affects: Design of the 1969 fuel-cell water separator
      source: nasa-tech-brief-1969
      where: Article text
  handling:
    - text: Dust is combustible; finely divided palladium catalysts are usually pyrophoric and need appropriate handling precautions. PubChem lists incompatibilities with arsenic, carbon, ozonides, methanol and sulfur, and reports explosive reaction with hydrogen and hydrogen peroxide.
      source: pubchem-pd
      where: Fire Potential; Explosive Limits and Potential; Hazardous Reactivities and Incompatibilities
  mitigations:
    - text: PubChem's disposal note advises using an alternative chemical with less propensity for occupational exposure where possible and recycling unused portions.
      source: pubchem-pd
      where: Accidental Release Measures > Disposal Methods
uses:
  - application: electronics-and-chips
    device: Multilayer ceramic capacitors and hybridised integrated circuits
    example: The USGS lists electronic applications of platinum-group metals such as computer hard disks, hybridized integrated circuits and multilayer ceramic capacitors. Palladium is one of the six metals in that chapter.
    source: usgs-mcs2025-pgm
    where: Domestic Production and Use
  - application: electronics-and-chips
    device: Printed circuit boards of mobile phones
    example: A Swedish study aqua-regia-leached boards from 30 mobile phones and 30 smartphones and found 119 ppm and 55 ppm palladium respectively.
    source: holgersson2018
    where: Abstract
  - application: electronics-and-chips
    device: Electrical contact material (supplier data for palladium)
    example: 'Deringer-Ney lists contact-resistance results for its palladium: 6 mOhm at 30 gf, unchanged after 1,000 h at 150 degC and 10 mOhm after 720 h in flowers of sulfur at 50 degC. The page does not name a product.'
    source: deringer-ney-pd
    where: Second constant-properties table
  - application: propulsion-and-tanks
    device: Palladium-silver separator for dissolved hydrogen in spacecraft fuel-cell water (NASA-sponsored, 1969 design)
    example: A separator of 75% palladium-25% silver alloy with palladium black coatings was built by The Garrett Corporation under contract to the Manned Spacecraft Center to remove dissolved hydrogen from alkaline fuel-cell water. A test unit ran more than 3700 hours.
    source: nasa-tech-brief-1969
    where: Article text and Source line
  - application: cryogenic-fuel
    device: Hydrogen purification membranes (laboratory and industrial)
    example: NASA Glenn's 2019 report says palladium is commonly used to purify hydrogen because only hydrogen readily passes through the bulk metal, and models permeation through a palladium-silver alloy.
    source: smith2019-nasa-tm
    where: Introduction and Summary
  - application: electronics-and-chips
    device: Catalysts for vehicles, bulk chemicals and petroleum refining
    example: The USGS lists catalytic converters as the leading domestic use of platinum-group metals and names catalysts for bulk-chemical production and petroleum refining. Palladium has substituted for platinum in most gasoline-engine catalytic converters.
    source: usgs-mcs2025-pgm
    where: Domestic Production and Use; Substitutes
supply:
  - subject: Palladium
    abundance: World mine production of palladium was 208,000 kg in 2023 and 190,000 kg (estimated) in 2024, of which Russia mined 75,000 kg, South Africa 72,000 kg, Canada 15,000 kg, Zimbabwe 15,000 kg and the United States 8,000 kg. For platinum the 2024 estimate was 170,000 kg, of which South Africa mined 120,000 kg and Russia 18,000 kg. PGM reserves (all platinum-group metals together, not palladium alone) are more than 81,000,000 kg, with the largest in South Africa (63,000,000 kg) and Russia (16,000,000 kg); world PGM resources are more than 100 million kg, largest in the Bushveld Complex of South Africa.
    producers:
      - country: Russia
        share_percent: 39.5
        year: 2024
      - country: South Africa
        share_percent: 37.9
        year: 2024
      - country: Canada
        share_percent: 7.9
        year: 2024
      - country: Zimbabwe
        share_percent: 7.9
        year: 2024
      - country: United States
        share_percent: 4.2
        year: 2024
      - country: Other countries
        share_percent: 2.2
        year: 2024
    critical_lists: []
    recycling: About 120,000 kg of palladium and platinum were recovered globally from new and old scrap in 2024, including about 45,000 kg of palladium and 8,500 kg of platinum from automobile catalytic converters in the United States (USGS).
    substitutes:
      - Palladium has substituted for platinum in most gasoline-engine catalytic converters; about 25% of palladium can routinely be substituted for platinum in diesel converters, up to 50% in some applications.
      - For some industrial end uses one PGM can substitute for another, with losses in efficiency.
    source: usgs-mcs2025-pgm
    where: World Mine Production and Reserves table; World Resources; Recycling; Substitutes. Producer shares are calculated by Space Mushroom as each country's 2024e kg divided by the 190,000 kg world total, so they sum to about 99.6% because the USGS total is rounded.
  - subject: Palladium (United States)
    abundance: US mine production of palladium was 8,000 kg (estimated) in 2024, down from 10,300 kg in 2023; US apparent consumption was 83,000 kg (estimated) and net import reliance 36% of apparent consumption in 2024. Palladium imports in 2020-23 came from Russia (32%), South Africa (32%), Belgium (8%) and Italy (8%).
    producers: []
    critical_lists: []
    recycling: 'See above: about 45,000 kg of palladium recovered from US automobile catalytic converters in 2024.'
    substitutes: []
    source: usgs-mcs2025-pgm
    where: Salient Statistics table; Import Sources (2020-23). The USGS also reports Russia as the world's leading producer of mined palladium and South Africa as the leading producer of PGM-containing mined material.
documents:
  - {title: "WebElements: Palladium, the essentials", type: database, url: "https://winter.group.shef.ac.uk/webelements/palladium/", year: 2026}
  - {title: "WebElements: Palladium, crystal structure", type: database, url: "https://winter.group.shef.ac.uk/webelements/palladium/crystal_structure.html", year: 2026}
  - title: 'USGS Mineral Commodity Summaries 2025: Platinum-Group Metals'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2025/mcs2025-platinum-group.pdf
    year: 2025
  - title: 'PubChem compound record: Palladium (CID 23938)'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Palladium
    year: 2026
  - title: 'Deringer-Ney: Palladium (precious metal alloy datasheet page)'
    type: datasheet
    url: https://deringerney.com/products/precious-metal-alloys/palladium/
    year: 2026
  - title: 'Goodfellow: High-Purity Palladium Metal'
    type: datasheet
    url: https://www.goodfellow.com/usa/material/precious-metals/palladium
    year: 2026
  - title: 'WebElements: Palladium physical properties'
    type: database
    url: https://winter.group.shef.ac.uk/webelements/palladium/physics.html
    year: 2026
  - title: Thin robust Pd membranes for low-temperature application (RSC Advances, PMC9043342)
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC9043342
    year: 2021
  - title: 'NASA/TM-2019-220189: Permeation Rate Equations for Hydrogen and Deuterium in a Palladium-Silver Alloy'
    type: report
    url: https://ntrs.nasa.gov/api/citations/20190030498/downloads/20190030498.pdf
    year: 2019
  - title: 'NASA Tech Brief B69-10635: Device Separates Hydrogen from Solution in Water at Ambient Temperatures'
    type: report
    url: https://ntrs.nasa.gov/api/citations/19690000580/downloads/19690000580.pdf
    year: 1969
  - title: Analysis of the metal content of small-size WEEE printed circuit-boards part 1 (Holgersson et al.; Chalmers record)
    type: paper
    url: https://research.chalmers.se/en/publication/502981
    year: 2018
gaps:
  - "The 2026 USGS palladium group metals PDF (https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-palladium-group-metals.pdf) returned a Page Not Found page in this run, so the refining route and 2026 supply figures were not read. The recipe names the ore source from Wikipedia only (nickel-copper deposits and catalytic-converter recycling), and no refining process is sourced."
  - 'Connector plating: no source opened states palladium or palladium-alloy connector plating directly; only Deringer-Ney contact-resistance data for palladium were found, so that use is described as electrical-contact material.'
  - 'Multilayer ceramic capacitors: the USGS only lists the capacitor use in a sentence. No source with the palladium or palladium-silver electrode content, or the mass of palladium per capacitor, was found.'
  - 'Annealed mechanical properties disagree: Deringer-Ney gives 280 MPa tensile and 270 MPa yield (annealed), Goodfellow gives 170-210 MPa and 60-120 MPa (temper not stated). No standard or paper was found to settle which is right, and no cold-worked values were sourced.'
  - No density, conductivity or modulus value was found with an explicit measurement temperature and method; the WebElements page states none, and the PubChem handbook entries give only the citation.
  - Hydrogen solubility versus pressure and temperature (the pressure-composition isotherms) and a numerical lattice parameter for the beta phase were not obtained; the open-access paper gives the H/Pd ratios but no lattice constants.
  - The NASA 2019 permeation equations (constants 4.22e-6 and 704 K for hydrogen, 2.12e-6 and 468 K for deuterium) were read from a text extraction in which the exponent layout is garbled, so they were not entered as a property. Check the PDF before using them.
  - The 1969 NASA separator is a fuel-cell water device from a design brief. No source was found on palladium hydrogen handling on current spacecraft (for example ISS life-support hardware), so no claim about present use is made.
  - 'Catalytic role: only the USGS use list was opened. No source on hydrogenation, cross-coupling or catalytic-converter chemistry (what palladium actually does, loadings, poisoning) was fetched; the Nobel Foundation release could not be opened (HTTP 403).'
  - USGS Mineral Commodity Summaries 2026 could not be read (the file fetched was a single page), so supply data are for 2024 estimates from the 2025 edition. The USGS critical minerals list status for palladium was not checked.
  - The Jandric et al. pXRF study of 45 phones (1998-2021) was found only through search-result text and could not be opened, so it is not cited. Only the Holgersson et al. abstract (read on the Chalmers page) is used for mobile-phone palladium.
  - No ECHA registration dossier or safety data sheet was opened; hazard data are PubChem aggregates only. No space-environment data (atomic oxygen, radiation, outgassing, vacuum cold welding) for palladium were found. No prices are shown.
sources:
  webelements-palladium-main:
    title: "Palladium - 46Pd: the essentials (WebElements, relative atomic mass)"
    url: https://winter.group.shef.ac.uk/webelements/palladium/
    year: 2026
    kind: database
    license: "WebElements, free online reference"
  webelements-palladium-crystal:
    title: "Palladium - 46Pd: crystal structure (WebElements)"
    url: https://winter.group.shef.ac.uk/webelements/palladium/crystal_structure.html
    year: 2026
    kind: database
    license: "WebElements, free online reference"
  wikipedia-palladium:
    title: "Palladium (Wikipedia, occurrence and history sections)"
    url: https://en.wikipedia.org/wiki/Palladium
    year: 2026
    kind: web
    license: "CC BY-SA 4.0"
  usgs-mcs2025-pgm:
    title: Mineral Commodity Summaries 2025, Platinum-Group Metals
    id: USGS MCS 2025, pp. 136-137 (data to 2024)
    url: https://pubs.usgs.gov/periodicals/mcs2025/mcs2025-platinum-group.pdf
    year: 2025
    kind: report
    license: public domain (USGS)
  pubchem-pd:
    title: PubChem compound record, Palladium (CID 23938)
    id: CID 23938; CAS 7440-05-3
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Palladium
    year: 2026
    kind: database
    license: public domain (NCBI); cited handbooks are not reproduced
  webelements-pd:
    title: WebElements, Palladium physical properties
    id: WebElements Periodic Table (University of Sheffield mirror)
    url: https://winter.group.shef.ac.uk/webelements/palladium/physics.html
    year: 2026
    kind: database
    license: web database, linked not reproduced
  deringer-ney-pd:
    title: Deringer-Ney, Palladium (precious metal alloy page)
    id: Supplier web page; references ASTM B 589-94 (Refined Palladium)
    url: https://deringerney.com/products/precious-metal-alloys/palladium/
    year: 2026
    kind: datasheet
    license: manufacturer document, linked not reproduced
  goodfellow-pd:
    title: Goodfellow, High-Purity Palladium Metal
    id: Supplier web page, General and Mechanical Properties tables
    url: https://www.goodfellow.com/usa/material/precious-metals/palladium
    year: 2026
    kind: datasheet
    license: manufacturer document, linked not reproduced
  ma2021-pd-membranes:
    title: Thin robust Pd membranes for low-temperature application
    id: doi:10.1039/d1ra06192e (RSC Advances 11(58), 36617-36624; PMC9043342)
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC9043342
    year: 2021
    kind: paper
    license: Royal Society of Chemistry copyright shown; open access on PubMed Central; no licence named on the page we read
  smith2019-nasa-tm:
    title: Permeation Rate Equations for Hydrogen and Deuterium in a Palladium-Silver Alloy
    id: NASA/TM-2019-220189, NTRS 20190030498
    url: https://ntrs.nasa.gov/api/citations/20190030498/downloads/20190030498.pdf
    year: 2019
    kind: report
    license: public domain (NASA)
  nasa-tech-brief-1969:
    title: Device Separates Hydrogen from Solution in Water at Ambient Temperatures
    id: NASA Tech Brief B69-10635 (MSC-13335), November 1969
    url: https://ntrs.nasa.gov/api/citations/19690000580/downloads/19690000580.pdf
    year: 1969
    kind: report
    license: public domain (NASA)
  holgersson2018:
    title: 'Analysis of the metal content of small-size Waste Electric and Electronic Equipment (WEEE) printed circuit-boards part 1: Internet routers, mobile phones and smartphones'
    id: doi:10.1016/j.resconrec.2017.02.011 (Resources, Conservation and Recycling 133, 300-308)
    url: https://research.chalmers.se/en/publication/502981
    year: 2018
    kind: paper
    license: publisher article; abstract read on the Chalmers research record, linked not reproduced
license: CC-BY-4.0
updated: '2026-10-17'
review:
  status: draft
  method: assistant
  checked_values: 22
  unreachable: 4
  caveats: 6
  note: 'Written by an AI assistant on 2026-10-17. USGS table values were read in text extracted from the PDF; PubChem values were read in its JSON record; the Holgersson abstract was read in the page HTML; NASA brief and NASA TM were read in extracted PDF text. Deringer-Ney, Goodfellow, WebElements and the RSC Advances paper were read once through a web-page summary and not independently re-read. Unreachable: USGS MCS 2026, MDPI Recycling 2020, Jandric et al. (RWTH), Nobel Foundation release. No values were taken from memory.'
story:
  risk_groups:
    - title: For people
      level: 2
      verdict: Mixed classification; fine powder burns
      lead: Solid palladium is a mild concern, but the dust and especially palladium black catalysts can ignite, and the metal can sensitise skin.
      points:
        - label: Classification
          line: 'PubChem aggregates 616 supplier reports: 59.3% say palladium does not meet GHS hazard criteria and 31.5% label it a flammable solid (H228). The classification depends on the supplier and the form.'
        - label: Skin
          line: Contact dermatitis has been associated with metallic palladium, especially palladium alloys, and the metal is called a possible skin sensitiser. Occupational asthma has been reported but is very rare.
        - label: Fire
          line: Dust is combustible, and finely divided palladium black used as a hydrogenation catalyst is usually pyrophoric. A reported fire started when 10% palladium on carbon met methanol in a hydrogen-filled flask.
    - title: If it fails
      lead: The documented failure is hydrogen embrittlement of pure palladium, studied in membranes and not in spacecraft parts.
      points:
        - label: Hydrogen embrittlement
          line: Below about 293 degC and under 20 bar of hydrogen, the hydrogen-rich beta phase grows inside the hydrogen-poor alpha phase. The lattice expands by more than 10% in the transition, and the resulting stress warps and destroys pure Pd membranes.
        - label: Alloy fix
          line: NASA notes that palladium purification membranes are typically alloyed with silver to protect strength and shape against hydrogen, and that 25 percent silver gives a good balance.
        - label: Thin tubes
          line: In the same paper, hollow fibre membranes 2 mm in outer diameter and under 4 micrometres thick resisted embrittlement below 100 degC.
    - title: Handling and storage
      points:
        - label: Catalyst powders
          line: Treat palladium black and palladium on carbon as pyrophoric and keep them away from methanol and other organic solvents when hydrogen is present.
        - label: Incompatibilities
          line: PubChem lists arsenic, carbon, ozonides, methanol and sulfur as incompatible, and an explosive reaction with hydrogen and hydrogen peroxide.
        - label: Disposal
          line: Recycle unused portions where possible, as PubChem's disposal note advises.
  why: 'Palladium is a platinum-group metal with a face-centred cubic crystal structure and a lattice parameter of 3.891 angstroms. It is dense (12.02 g/cm3), melts at 1554.9 degC and boils at 2963 degC. Annealed, it is soft: a supplier datasheet gives a tensile strength of 280 MPa, 25% elongation and a Vickers hardness of 40. Its electrical conductivity is 16% of the International Annealed Copper Standard, and its thermal conductivity is about 72 W/(m.K). What sets it apart is hydrogen. The metal absorbs hydrogen into its crystal lattice, up to about 0.7 hydrogen atoms per palladium atom at 25 degC and 1 bar in the beta phase, and only hydrogen readily passes through the bulk metal, which is why it is used to purify hydrogen. The same absorption swells the lattice by more than 10% in the alpha-to-beta transition and can crack pure palladium, so purification membranes are usually alloyed with silver.'
  uses:
    - where: Capacitors and chips
      line: The USGS lists multilayer ceramic capacitors and hybridised integrated circuits among electronic uses of the platinum-group metals, which include palladium. It gives no palladium content per part.
    - where: Mobile-phone circuit boards
      line: A published study leached boards from 30 mobile phones and 30 smartphones in aqua regia and measured palladium at 119 ppm and 55 ppm. Older phone boards held more palladium than newer ones.
    - where: Spacecraft fuel-cell water
      line: In 1969 a separator of palladium-silver alloy coated with palladium black was built under a Manned Spacecraft Center contract to remove dissolved hydrogen from alkaline fuel-cell water. A test unit ran more than 3700 hours without loss of efficiency.
    - where: Catalysts
      line: The USGS names catalytic converters as the leading domestic use of platinum-group metals, and lists catalysts for bulk chemicals and petroleum refining. Palladium has replaced platinum in most gasoline-engine converters.
  can_do:
    - label: Hydrogen passage
      value: Dissolved H2 from 60 to under 0.5 psia
      line: The 1969 NASA-sponsored separator, made from 75% palladium-25% silver tubes with palladium black, lowered the partial pressure of hydrogen dissolved in water from 60 psia to less than 0.5 psia at 75 degF and 10 ml per minute of flow.
    - label: Hydrogen uptake
      value: About 0.7 H per Pd
      line: At 25 degC and 1 bar the beta phase holds a hydrogen-to-palladium ratio of about 0.7, against about 0.015 for the alpha phase, according to an open-access paper on palladium membranes.
    - label: Conducting
      value: 10.8 microohm-cm
      line: Deringer-Ney gives a resistivity of 10.8 microohm-cm and 16% IACS conductivity. WebElements gives a thermal conductivity of 72 W/(m.K), with Goodfellow at 71.8 and Deringer-Ney at 70.
    - label: Stability of contacts
      value: 6 mOhm at 30 gf
      line: The same supplier lists a contact resistance of 6 mOhm at 30 gf that stayed at 6 mOhm after 1,000 hours at 150 degC, and 10 mOhm after 720 hours in flowers of sulfur at 50 degC.
    - label: Supply
      value: 190,000 kg in 2024
      line: The USGS estimates world mine production of palladium at 190,000 kg in 2024, with Russia at 75,000 kg and South Africa at 72,000 kg.
  compare: Within the sources collected here, palladium's 2024 world mine production (190,000 kg, estimated) is slightly above platinum's 170,000 kg, and palladium is far more concentrated in Russia (75,000 kg) than platinum is (18,000 kg), where South Africa leads with 120,000 kg. The 2019 NASA report says palladium is commonly alloyed with silver for hydrogen membranes, with 25 percent silver a good balance. No source collected here compares palladium's mechanical properties with those of other metals, so no such comparison is made.
  handling:
    - Treat fine palladium powders and palladium black as pyrophoric; keep them away from methanol and hydrogen together.
    - Expect a possible skin sensitiser, especially in palladium alloys.
    - Plan for hydrogen to be absorbed and for the lattice to swell; alloy with silver or keep membranes away from the cool, pressurised alpha-beta region.
    - Recycle scrap; the USGS counts about 45,000 kg of palladium recovered from US car catalysts in 2024.
  good_for:
    - Catalysis and hydrogen separation. Only hydrogen readily passes through bulk palladium, and a palladium-silver separator ran 3700 hours in a NASA-sponsored test.
    - Electrical contacts. A supplier lists 6 mOhm contact resistance at 30 gf, and 16% IACS conductivity.
    - Recyclability. About 120,000 kg of palladium and platinum were recovered from scrap worldwide in 2024.
  watch_out:
    - Hydrogen embrittlement. Pure palladium expands by more than 10% in volume when the hydride phase forms, and membranes warp and fracture.
    - Supply concentration. Russia and South Africa together make up about 77% of 2024 estimated world mine production (calculated from the USGS table).
    - Spread in datasheet strength. Two suppliers disagree on annealed strength (280 MPa against 170-210 MPa), so check the grade and temper.
    - Powder fire risk. Palladium black is usually pyrophoric.
  verdict: Palladium is a dense, soft, catalytic metal that is used where hydrogen has to be passed, purified or reacted, and where stable electrical contacts are needed, but it absorbs hydrogen enough to swell and crack when used unalloyed, and mining is concentrated in Russia and South Africa. The spacecraft evidence found here is one 1969 NASA-sponsored fuel-cell water separator and a 2019 NASA permeation model; no flight data on palladium in modern spacecraft were found.
  compare_rows:
    - label: Density
      benchmark: density
      scope: material
    - label: Melting point
      benchmark: melting_point
      scope: material
    - label: Thermal conductivity
      benchmark: thermal_conductivity
      scope: material
  recipe:
    line: >-
      Palladium is the element Pd, atomic number 46, a platinum-group metal with cubic close-packed crystals (ccp, space group Fm-3m, WebElements). Wikipedia says the most important commercial sources are nickel-copper deposits, and that recycling, mostly of scrapped catalytic converters, is also a source. The refining route was not read in this run; the Wikipedia history section describes only the early laboratory isolation from aqua regia, which is not a production process.
    parts:
      - name: Palladium
        symbol: Pd
        atoms: 1
        atomic_weight: 106.42
        role: "The whole material. WebElements prints the relative atomic mass on its main page."