spore: profile
id: germanium-telluride
spore_version: 0.2
family: phase-change-chalcogenides
name: Germanium telluride (GeTe)
abbreviation: GeTe
role: phase-change memory material and thermoelectric
category: energy
type: thermoelectrics
summary: |
  GeTe is germanium telluride, one germanium atom bonded to one tellurium atom, with a rhombohedral crystal structure at room temperature. Its density is 6.14 g/cm3 in the Wikipedia infobox and 6.2 g/cc as a theoretical density on an evaporation-material datasheet, and both sources give a melting point of 725 °C. Gwin and Coutu report a transition at approximately 200 °C that they use for electronic memory. Calculations give a room-temperature zT of 0.39 for n-type cross-plane GeTe; these are calculated values, not measurements.
best_for: Phase-change memory research and thermoelectric modelling, where the sources give a switching transition near 200 °C and calculated zT figures
weakest_at: 'Few measured transport values for pure GeTe in the sources read here: the thermoelectric figures are calculated, and no corrosion or space test was found'
identity:
  formula: GeTe
  cas: 12025-39-7
  crystal_system: rhombohedral
  space_group: R3m
  source: wikipedia-gete
  where: 'Infobox: crystal structure rhombohedral (Pearson symbol hR6), space group R3m, No. 160; chemical formula GeTe; CAS number 12025-39-7'
tags:
  environments: []
  stresses: []
  applications:
    - electronics-and-chips
    - optics-and-cameras
properties:
  - benchmark: density
    label: Density
    value: 6.14
    unit: g/cm3
    scope: material
    conditions:
      basis: 'standard-state conditions printed in the infobox: 25 °C and 100 kPa'
    method: Value printed in the Wikipedia infobox (Density field)
    status: ground
    source: wikipedia-gete
    where: Infobox, Density
  - benchmark: density
    label: Theoretical density
    value: 6.2
    unit: g/cc
    scope: material
    conditions:
      basis: printed as Theoretical Density on the product page; not stated whether measured or calculated
    method: Value printed on the AEM Deposition product page as Theoretical Density
    status: ground
    source: aem-gete
    where: Product table, Theoretical Density row
  - benchmark: melting_point
    label: Melting point
    value: 725
    unit: °C
    scope: material
    conditions:
      basis: printed in the Wikipedia infobox as 725 °C (1,337 °F; 998 K)
    method: Value printed in the Wikipedia infobox (Melting point field)
    status: ground
    source: wikipedia-gete
    where: Infobox, Melting point
  - benchmark: melting_point
    label: Melting point
    value: 725
    unit: °C
    scope: material
    conditions:
      basis: printed on the product page as Melting Point; no pressure stated
    method: Value printed on the AEM Deposition product page
    status: ground
    source: aem-gete
    where: Product table, Melting Point row
  - benchmark: band_gap
    label: Band gap
    value: 0.6
    unit: eV
    scope: material
    conditions:
      basis: printed in the infobox without a temperature
    method: Value printed in the Wikipedia infobox (Band gap field)
    status: ground
    source: wikipedia-gete
    where: Infobox, Band gap
  - benchmark: band_gap
    label: Direct band gap (as cited)
    value: 0.6
    unit: eV
    scope: material
    conditions:
      basis: described as a direct bandgap; the paper gives this as the experimental value it compares against
    method: Value stated in the abstract of an arXiv preprint that models a GeTe thermophotovoltaic cell
    status: ground
    source: abir-2023
    where: Abstract
  - benchmark: curie_temperature
    label: Ferroelectric Curie temperature
    value: 397
    unit: °C
    scope: material
    conditions:
      basis: printed as approximately 670 K (746 °F; 397 °C); below this temperature the alpha phase is the dominant form of pure GeTe
    method: Value printed in the body text of the Wikipedia article
    status: ground
    source: wikipedia-gete
    where: Body text, ferroelectric Curie temperature paragraph
  - benchmark: rhombohedral_to_cubic_transition_temperature
    label: Rhombohedral to cubic transition
    value: 640
    unit: K
    scope: material
    conditions:
      basis: printed as above approximately 640 K (with a tilde); the paper gives it as the temperature at which the rhombohedral phase changes to a cubic rock-salt structure
    method: Value stated in the introduction of an arXiv preprint on GeTe thermoelectric transport
    status: ground
    source: askarpour-maassen-2019
    where: Introduction, first paragraph
  - benchmark: memory_transition_temperature
    label: Transition temperature in memory devices
    value: 200
    unit: °C
    scope: material
    conditions:
      basis: printed as approximately 200 °C; the abstract gives no film thickness, pressure or time
    method: Value stated in the abstract of a SPIE conference paper on electronic control of the GeTe phase transition
    status: ground
    source: gwin-coutu-2015
    where: Abstract
  - benchmark: lattice_parameter_a
    label: Lattice constant a
    value: 4.1719
    unit: Å
    scope: material
    conditions:
      phase: rhombohedral alpha phase (Pearson symbol hR6)
    method: Value printed in the Wikipedia infobox (lattice constants)
    status: ground
    source: wikipedia-gete
    where: Infobox, Lattice constants
  - benchmark: lattice_parameter_c
    label: Lattice constant c
    value: 10.71
    unit: Å
    scope: material
    conditions:
      phase: rhombohedral alpha phase (Pearson symbol hR6)
    method: Value printed in the Wikipedia infobox (lattice constants)
    status: ground
    source: wikipedia-gete
    where: Infobox, Lattice constants
  - benchmark: molar_mass
    label: Molar mass
    value: 200.21
    unit: g/mol
    scope: material
    conditions:
      basis: printed as molar mass of the GeTe formula
    method: Value printed in the Wikipedia infobox (Molar mass field)
    status: ground
    source: wikipedia-gete
    where: Infobox, Molar mass
  - benchmark: refractive_index
    label: Refractive index (TPV model input)
    value: 5.5
    unit: '-'
    scope: material
    conditions:
      basis: printed as a parameter in the device table with its reference [37]; no wavelength stated
    method: Input value printed in the parameter table of an arXiv preprint on a GeTe thermophotovoltaic cell
    status: ground
    source: abir-2023
    where: Simulation parameter table, refractive index row
  - benchmark: refractive_index
    label: Refractive index (n_D)
    value: 5
    unit: '-'
    scope: material
    conditions:
      basis: printed as 5 without a unit or wavelength in the infobox (n_D)
    method: Value printed in the Wikipedia infobox; it differs from the 5.5 used in the TPV preprint
    status: ground
    source: wikipedia-gete
    where: Infobox, Refractive index (n_D)
  - benchmark: dielectric_constant
    label: Dielectric constant
    value: 40
    unit: '-'
    scope: material
    conditions:
      basis: printed without a frequency or temperature; the preprint cites its reference [6] for the value
    method: Value stated in the body text of an arXiv preprint on a GeTe thermophotovoltaic cell
    status: ground
    source: abir-2023
    where: Introduction, paragraph on GeTe properties
  - benchmark: seebeck_coefficient
    label: Seebeck coefficient at the band edges
    value: 200
    unit: µV/K
    scope: material
    conditions:
      basis: absolute value at the band edges of rhombohedral GeTe, 300 K, from a density-functional transport calculation (not measured)
    method: Calculated value stated in the Results of an arXiv preprint (Askarpour and Maassen); the paper states the absolute value approximately
    status: calculated
    source: askarpour-maassen-2019
    where: Section on thermoelectric transport properties
  - benchmark: figure_of_merit_zt
    label: Room-temperature zT, n-type cross-plane
    value: 0.39
    unit: '-'
    scope: material
    conditions:
      basis: n-type, cross-plane direction, 300 K, optimal carrier concentration; density-functional transport calculation (not measured)
    method: Calculated value stated in the Discussion of an arXiv preprint (Askarpour and Maassen); the paper's in-plane n-type value is 0.13
    status: calculated
    source: askarpour-maassen-2019
    where: Discussion, first list of optimal room-temperature zT values
corrosion: []
risks:
  hazards:
    - text: 'PubChem''s GHS summary lists H302 (100%): Harmful if swallowed, with signal word Warning, from 56 company reports to the ECHA C&L Inventory (2 notifications).'
      ghs:
        - H302
      source: pubchem-gete
      where: Safety and Hazards, GHS Classification (CID 16213264)
    - text: PubChem lists precautionary statement codes P264, P270, P301+P317, P330 and P501; the statement texts are behind links on that page and were not read in this run.
      ghs: []
      source: pubchem-gete
      where: Safety and Hazards, GHS Classification, Precautionary Statement Codes
  failure_risks:
    - mode: Phase change at the memory transition temperature
      trigger: Heating a GeTe film to its transition temperature
      consequence: The abstract gives the transition temperature as approximately 200 °C and does not state what happens to stored data above it.
      severity: moderate
      source: gwin-coutu-2015
      where: Abstract
    - mode: Rhombohedral to cubic phase change
      trigger: Heating GeTe above approximately 640 K
      consequence: The calculations model only the rhombohedral phase, the room-temperature form, so the calculated Seebeck and zT values do not describe the material above this temperature.
      severity: low
      source: askarpour-maassen-2019
      where: Introduction and Section on thermoelectric transport properties
  side_effects: []
  handling:
    - text: No supplier safety data sheet for GeTe was read in this run, so the hazard entries above rest on PubChem's GHS summary alone.
      source: pubchem-gete
      where: Safety and Hazards (CID 16213264)
    - text: AEM Deposition sells GeTe as pellets, pieces and powder for thermal evaporation; its product page gives no storage or handling text.
      source: aem-gete
      where: Product description and availability
uses:
  - application: electronics-and-chips
    device: Phase-change electronic memory (research)
    example: Gwin and Coutu's paper is titled 'Electronic control of Germanium Telluride (GeTe) phase transition for electronic memory applications'. Its abstract reports a transition temperature of approximately 200 °C.
    source: gwin-coutu-2015
    where: Title and abstract
  - application: electronics-and-chips
    device: Single-junction thermophotovoltaic cell (theoretical)
    example: Abir and co-authors model a GeTe thermophotovoltaic cell, a device that converts radiated heat into electricity, using a direct bandgap of 0.6 eV. The work is a theoretical calculation.
    source: abir-2023
    where: Abstract and Introduction
supply:
  - subject: Germanium
    producers: []
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (germanium named on the list)
        listed: true
    recycling: 'USGS: the United States can recycle new and old germanium scrap, but available information was inadequate to make reliable estimates of the amount of secondary germanium produced.'
    substitutes:
      - 'USGS: silicon or gallium arsenide can substitute for germanium in certain electronic applications, and chalcogenide glass has been used as a substitute for germanium metal in infrared applications.'
    source: usgs-mcs2026-germanium
    where: Events, Trends, and Issues (China named as the leading producer and exporter of germanium metal in 2025, without a share); World Refinery Production and Reserves; Recycling; Substitutes
  - subject: Tellurium
    producers:
      - country: China
        share_percent: 80
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (tellurium named on the list)
        listed: true
    recycling: 'USGS: tellurium was recycled from CdTe solar cells in the United States, but the quantity was limited because most of these cells were relatively new.'
    substitutes:
      - 'USGS: bismuth selenide and organic polymers can substitute for bismuth telluride in some thermoelectric devices.'
    source: usgs-mcs2026-tellurium
    where: 'Summary: China accounted for 80% of estimated global production in 2025; Recycling; Substitutes'
media: []
documents:
  - title: 'AEM Deposition: Germanium Telluride pellet evaporation material (product page)'
    type: datasheet
    url: https://www.aemdeposition.com/compound-evaporation-material/germanium-telluride-evaporation-material.html
    year: 2026
  - title: 'PubChem: Germanium telluride (GeTe), CID 16213264, GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/16213264
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Germanium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-germanium.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Tellurium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tellurium.pdf
    year: 2026
  - title: Electronic control of Germanium Telluride (GeTe) phase transition for electronic memory applications (Gwin and Coutu)
    type: paper
    url: https://epublications.marquette.edu/electric_fac/404
    year: 2015
  - title: Unusual thermoelectric transport anisotropy in quasi-2D, rhombohedral GeTe (arXiv:1904.06439)
    type: paper
    url: https://arxiv.org/abs/1904.06439
    year: 2019
  - title: Exploring the potential of GeTe for the application in Thermophotovoltaic (TPV) cell (arXiv:2301.08896)
    type: paper
    url: https://arxiv.org/abs/2301.08896
    year: 2023
gaps:
  - Corrosion, oxidation and ageing of GeTe were not found in any source read in this run; the failure modes cover the phase-transition temperatures only.
  - The thermoelectric figures are calculated (density-functional theory). No measured zT for undoped GeTe was read in this run. A higher measured zT for an alloyed GeTe is cited in the 2019 preprint and is left out because it is a different composition.
  - The TPV preprint's electrical resistivity figure is printed with an exponent, so it is left out under the rule for exponent values.
  - No measured Seebeck coefficient, thermal conductivity or electrical resistivity for undoped GeTe, with units, was found in any source read in this run.
  - No supplier safety data sheet for GeTe was read; the only hazard source is PubChem's GHS summary, which lists no pictograms in the text read.
  - The USGS germanium summary names China as the leading producer and exporter of germanium metal in 2025 but gives no production share, so no producer percentages are recorded for germanium.
  - Lattice constants, molar mass, band gap, refractive index, Seebeck coefficient and zT use snake_case benchmark names because they are not in property-canon; the refractive index differs between the Wikipedia infobox and the TPV preprint and both are kept.
  - 'Two sources could not be read by the script: the FUSNano product page returned no content, and the MDPI and American Elements pages returned HTTP 403.'
sources:
  wikipedia-gete:
    title: 'Germanium telluride (Wikipedia article: infobox, body text and references)'
    id: Wikipedia, read 2026-11-02
    url: https://en.wikipedia.org/wiki/Germanium_telluride
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  aem-gete:
    title: Germanium Telluride Pellet Evaporation Material (GeTe), AEM Deposition product page
    id: AEM Deposition product page, undated; read 2026-11-02
    url: https://www.aemdeposition.com/compound-evaporation-material/germanium-telluride-evaporation-material.html
    year: 2026
    kind: datasheet
    license: supplier page, cited not reproduced
  pubchem-gete:
    title: 'PubChem compound record, Germanium telluride (GeTe), CID 16213264: identifiers and GHS classification'
    id: CID 16213264; CAS 12025-39-7
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/16213264/JSON
    year: 2026
    kind: database
    license: public domain (NCBI)
  usgs-mcs2026-germanium:
    title: Mineral Commodity Summaries 2026, Germanium
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-germanium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-tellurium:
    title: Mineral Commodity Summaries 2026, Tellurium
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tellurium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  gwin-coutu-2015:
    title: Electronic control of Germanium Telluride (GeTe) phase transition for electronic memory applications
    id: doi:10.1117/12.2079359 (Proc. SPIE 9364, 93640G)
    url: https://epublications.marquette.edu/electric_fac/404
    year: 2015
    kind: paper
    license: repository record (abstract read)
  askarpour-maassen-2019:
    title: Unusual thermoelectric transport anisotropy in quasi-2D, rhombohedral GeTe
    id: arXiv:1904.06439 (v2)
    url: https://arxiv.org/pdf/1904.06439
    year: 2019
    kind: paper
    license: arXiv preprint (license as listed on arXiv)
  abir-2023:
    title: Exploring the potential of GeTe for the application in Thermophotovoltaic (TPV) cell
    id: arXiv:2301.08896 (v1)
    url: https://arxiv.org/pdf/2301.08896
    year: 2023
    kind: paper
    license: arXiv preprint (license as listed on arXiv)
license: CC-BY-4.0
updated: '2026-11-02'
review:
  status: draft
  method: assistant
  checked_values: 17
  note: 'Read by an AI assistant on 2026-11-02 from pages fetched in this run: 17 of 17 benchmark values found in their cited sources by verify-values; 0 sources unreadable; 0 values not found. Thermoelectric values are calculated, not measured.'
story:
  recipe:
    line: GeTe is germanium telluride, formed from one germanium atom bonded to one tellurium atom. The sources read here do not describe the synthesis route used for the commercial powder or evaporation material.
    parts:
      - name: Germanium
        symbol: Ge
        role: The group-14 element that forms one half of the compound, bonded to tellurium in the rhombohedral lattice.
      - name: Tellurium
        symbol: Te
        role: The group-16 element that forms the other half of the compound; tellurium is also the byproduct element in the supply section.
  risk_groups:
    - title: For people
      level: 0
      verdict: Harmful if swallowed (PubChem H302)
      lead: PubChem's hazard summary lists H302 for GeTe, based on company notifications. No supplier safety data sheet was read in this run.
      points:
        - label: Ingestion
          line: 'PubChem''s GHS summary lists H302 (100%): Harmful if swallowed, with the signal word Warning, from 56 company reports.'
        - label: Precautions
          line: PubChem lists precautionary codes P264, P270, P301+P317, P330 and P501. The statement texts were not read.
    - title: In a device
      lead: These are device-level statements from the papers read here. The sources do not report field incidents.
      points:
        - label: Transition temperature
          line: The memory transition is described at approximately 200 °C in the Gwin and Coutu abstract.
        - label: Phase change
          line: Above approximately 640 K the rhombohedral phase changes to a cubic rock-salt structure, so the room-temperature calculations no longer describe the material.
    - title: Handling and supply
      points:
        - label: Form
          line: AEM Deposition sells GeTe as pellets, pieces and powder. Its product page gives no storage or safety text.
        - label: Supply
          line: China accounted for 80% of estimated global tellurium production in 2025, according to the USGS summary.
  why: Germanium telluride (GeTe) is a compound of germanium and tellurium that switches between structures with very different electrical properties. Gwin and Coutu tie its phase transition to electronic memory. The same compound has also been studied as a thermoelectric material and as the absorber of a theoretical thermophotovoltaic cell. The sources read here give datasheet and reference values for density, melting point and band gap, and calculated values for its thermoelectric performance. It is the simpler two-element member of the phase-change family, to which its sibling Ge2Sb2Te5 also belongs.
  uses:
    - where: Electronic memory research
      line: Gwin and Coutu's 2015 paper is titled 'Electronic control of Germanium Telluride (GeTe) phase transition for electronic memory applications'. Its abstract reports a transition temperature at approximately 200 °C, and a resistivity that decreases by as much as six orders of magnitude.
    - where: Thermophotovoltaic cell (theory)
      line: Abir and co-authors calculate a single-junction GeTe thermophotovoltaic cell, a device that converts radiated heat into electricity, starting from a direct band gap of 0.6 eV. The work is a theoretical calculation, not a fabricated device.
  can_do:
    - label: Electronic memory
      benchmark: memory_transition_temperature
      value: 200 °C
      line: Switch between two structural states whose resistivity differs strongly, which the Gwin and Coutu abstract ties to electronic memory. The abstract gives the transition temperature as approximately 200 °C.
    - label: Band gap
      benchmark: band_gap
      value: 0.6 eV
      line: Act as a semiconductor with a direct band gap of 0.6 eV (Wikipedia infobox; Abir and co-authors).
    - label: Thermoelectric zT
      benchmark: figure_of_merit_zt
      value: '0.39'
      line: Reach a calculated room-temperature zT of 0.39 for n-type cross-plane material (Askarpour and Maassen, 2019; calculated, not measured).
  compare: 'GeTe is the two-element compound of this pair: the sibling Ge2Sb2Te5 profile adds antimony to the same germanium and tellurium. Among the values in this profile, the melting point of 725 °C and the density of 6.14 g/cm3 are datasheet or reference values, while the thermoelectric figures are calculated. The band gap of 0.6 eV is the same in the infobox and in the thermophotovoltaic preprint, and the refractive index is given as 5 in one source and 5.5 in the other.'
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Band gap
      benchmark: band_gap
  handling:
    - No supplier safety data sheet for GeTe was read in this run, so the hazard entries rest on PubChem's GHS summary alone.
    - AEM Deposition sells GeTe as pellets, pieces and powder for thermal evaporation; its page gives no storage or handling text.
    - PubChem lists H302 (harmful if swallowed); the precautionary statement texts behind its codes were not read.
  good_for:
    - Phase-change memory research, where the Gwin and Coutu abstract describes electronic control of the GeTe transition at approximately 200 °C.
    - Thermoelectric modelling, where the calculated room-temperature zT of 0.39 gives a baseline for n-type cross-plane GeTe.
  watch_out:
    - The thermoelectric figures are calculated, not measured, and the calculations model only the rhombohedral phase below approximately 640 K.
    - The Seebeck coefficient of about 200 µV/K at the band edges is a calculated value (Askarpour and Maassen), not a measured one.
    - The refractive index is 5 in the Wikipedia infobox and 5.5 in the TPV preprint's parameter table, and neither gives a wavelength.
  verdict: GeTe has enough sourced data for a phase-change and thermoelectric profile. Its thermoelectric figures are calculated, and its only hazard source is PubChem's summary.