Germanium telluride (GeTe) GeTe
GeTe · CAS 12025-39-7 · rhombohedral, R3m
GeTe is germanium telluride, one germanium atom bonded to one tellurium atom, with a rhombohedral crystal structure at room temperature.
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Electronic memory
200 °C
Band gap
0.6 eV
Thermoelectric zT
0.39
Recipe, share of the weight
- Ge not statedGermanium
- Te not statedTellurium
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
Risk at a glance
- People None found. Harmful if swallowed (PubChem H302)
- If it fails Moderate. Phase change at the memory transition temperature
- Corrosion No data. No corrosion data recorded
Quick facts: GeTe
| Property | Value | Basis |
|---|---|---|
| Density | 6.14 to 6.2 g/cm³ | 2 sourced values across conditions |
| Melting point | 725 °C | 1 sourced value |
What is the density of Germanium telluride (GeTe)?
Germanium telluride (GeTe) has a density of 6.14 to 6.2 g/cm³. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the melting point of Germanium telluride (GeTe)?
Germanium telluride (GeTe) has a melting point of 725 °C. The source and test conditions are listed in the properties table on this page.
What is Germanium telluride (GeTe) used for?
Uses recorded in the sources include Phase-change electronic memory (research); Single-junction thermophotovoltaic cell (theoretical).
Why it exists
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.
Where it's used
Electronic memory research
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.
Thermophotovoltaic cell (theory)
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.
Recipe
GeTe
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.
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Germanium Ge | not stated | The group-14 element that forms one half of the compound, bonded to tellurium in the rhombohedral lattice. |
| Tellurium Te | not stated | The group-16 element that forms the other half of the compound; tellurium is also the byproduct element in the supply section. |
Weight shares are as printed in the sources.
What it can do
Electronic memory
200 °C
measured
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.
Band gap
0.6 eV
measured
Act as a semiconductor with a direct band gap of 0.6 eV (Wikipedia infobox; Abir and co-authors).
Thermoelectric zT
0.39
worked out from the formula
Reach a calculated room-temperature zT of 0.39 for n-type cross-plane material (Askarpour and Maassen, 2019; calculated, not measured).
How it compares
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.
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details.
| Measurement | GeTe |
|---|---|
| Thermal behavior and safety | |
| Melting point | 725 °C3 |
| Melting pointValue printed on the AEM Deposition product page | 725 °C |
| Physical and electrical | |
| Density | 6.14 g/cm³1 |
| Theoretical density | 6.2 g/cc2 |
| Temperature behavior | |
| Ferroelectric Curie temperature | 397 °C6 |
| Rhombohedral to cubic transition | 640 K7 |
| Transition temperature in memory devices | 200 °C8 |
| Other measurements | |
| Band gap | 0.6 eV4 |
| Direct band gap (as cited) | 0.6 eV5 |
| Lattice constant a | 4.172 Å9 |
| Lattice constant c | 10.71 Å10 |
| Molar mass | 200.2 g/mol11 |
| Refractive index (TPV model input) | 5.5 -12 |
| Refractive index (n_D) | 5 -13 |
| Dielectric constant | 40 -14 |
| Seebeck coefficient at the band edges | 200 µV/K15 |
| Room-temperature zT, n-type cross-plane | 0.39 -16 |
Why choose it, and why not
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 for
- 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.
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.
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Density | Value printed in the Wikipedia infobox (Density field) | basis standard-state conditions printed in the infobox: 25 °C and 100 kPa | — |
| 2 | Theoretical density | Value printed on the AEM Deposition product page as Theoretical Density | basis printed as Theoretical Density on the product page; not stated whether measured or calculated | — |
| 3 | Melting point | Value printed in the Wikipedia infobox (Melting point field) | basis printed in the Wikipedia infobox as 725 °C (1,337 °F; 998 K) | — |
| 4 | Band gap | Value printed in the Wikipedia infobox (Band gap field) | basis printed in the infobox without a temperature | — |
| 5 | Direct band gap (as cited) | Value stated in the abstract of an arXiv preprint that models a GeTe thermophotovoltaic cell | basis described as a direct bandgap; the paper gives this as the experimental value it compares against | — |
| 6 | Ferroelectric Curie temperature | Value printed in the body text of the Wikipedia article | basis printed as approximately 670 K (746 °F; 397 °C); below this temperature the alpha phase is the dominant form of pure GeTe | — |
| 7 | Rhombohedral to cubic transition | Value stated in the introduction of an arXiv preprint on GeTe thermoelectric transport | 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 | — |
| 8 | Transition temperature in memory devices | Value stated in the abstract of a SPIE conference paper on electronic control of the GeTe phase transition | basis printed as approximately 200 °C; the abstract gives no film thickness, pressure or time | — |
| 9 | Lattice constant a | Value printed in the Wikipedia infobox (lattice constants) | phase rhombohedral alpha phase (Pearson symbol hR6) | — |
| 10 | Lattice constant c | Value printed in the Wikipedia infobox (lattice constants) | phase rhombohedral alpha phase (Pearson symbol hR6) | — |
| 11 | Molar mass | Value printed in the Wikipedia infobox (Molar mass field) | basis printed as molar mass of the GeTe formula | — |
| 12 | Refractive index (TPV model input) | Input value printed in the parameter table of an arXiv preprint on a GeTe thermophotovoltaic cell | basis printed as a parameter in the device table with its reference [37]; no wavelength stated | — |
| 13 | Refractive index (n_D) | Value printed in the Wikipedia infobox; it differs from the 5.5 used in the TPV preprint | basis printed as 5 without a unit or wavelength in the infobox (n_D) | — |
| 14 | Dielectric constant | Value stated in the body text of an arXiv preprint on a GeTe thermophotovoltaic cell | basis printed without a frequency or temperature; the preprint cites its reference [6] for the value | — |
| 15 | Seebeck coefficient at the band edges | Calculated value stated in the Results of an arXiv preprint (Askarpour and Maassen); the paper states the absolute value approximately | basis absolute value at the band edges of rhombohedral GeTe, 300 K, from a density-functional transport calculation (not measured) | — |
| 16 | Room-temperature zT, n-type cross-plane | Calculated value stated in the Discussion of an arXiv preprint (Askarpour and Maassen); the paper's in-plane n-type value is 0.13 | basis n-type, cross-plane direction, 300 K, optimal carrier concentration; density-functional transport calculation (not measured) | — |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
PubChem's hazard summary lists H302 for GeTe, based on company notifications. No supplier safety data sheet was read in this run.
- Ingestion
- PubChem's GHS summary lists H302 (100%): Harmful if swallowed, with the signal word Warning, from 56 company reports.
- Precautions
- PubChem lists precautionary codes P264, P270, P301+P317, P330 and P501. The statement texts were not read.
In a device
These are device-level statements from the papers read here. The sources do not report field incidents.
- Transition temperature
- The memory transition is described at approximately 200 °C in the Gwin and Coutu abstract.
- Phase change
- Above approximately 640 K the rhombohedral phase changes to a cubic rock-salt structure, so the room-temperature calculations no longer describe the material.
Handling and supply
- Form
- AEM Deposition sells GeTe as pellets, pieces and powder. Its product page gives no storage or safety text.
- Supply
- China accounted for 80% of estimated global tellurium production in 2025, according to the USGS summary.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Phase change at the memory transition temperaturemoderate severity | Heating a GeTe film to its transition temperatureThe abstract gives the transition temperature as approximately 200 °C and does not state what happens to stored data above it. |
| Rhombohedral to cubic phase changelow severity | Heating GeTe above approximately 640 KThe 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. |
Handling and storage
- No supplier safety data sheet for GeTe was read in this run, so the hazard entries above rest on PubChem's GHS summary alone.
- AEM Deposition sells GeTe as pellets, pieces and powder for thermal evaporation; its product page gives no storage or handling text.
Supply and geography
How common the raw materials are and where they come from.
Germanium
- Critical mineral lists
- US: listed
- 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.
Tellurium
- Top producers (2025)
- China 80%
- Critical mineral lists
- US: listed
- 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.
Documents
Datasheets, safety data sheets, papers and standards you can open.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.
Show the full YAML
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.
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.
| # | Source | Type | Year | Used for |
|---|---|---|---|---|
| Germanium telluride (Wikipedia article: infobox, body text and references) | web | 2026 | 9 values | |
| Germanium Telluride Pellet Evaporation Material (GeTe), AEM Deposition product page | datasheet | 2026 | 3 values | |
| PubChem compound record, Germanium telluride (GeTe), CID 16213264: identifiers and GHS classification | database | 2026 | 3 values | |
| Mineral Commodity Summaries 2026, Germanium | report | 2026 | 1 value | |
| Mineral Commodity Summaries 2026, Tellurium | report | 2026 | 1 value | |
| Electronic control of Germanium Telluride (GeTe) phase transition for electronic memory applications | paper | 2015 | 3 values | |
| Unusual thermoelectric transport anisotropy in quasi-2D, rhombohedral GeTe | paper | 2019 | 4 values | |
| Exploring the potential of GeTe for the application in Thermophotovoltaic (TPV) cell | paper | 2023 | 4 values |
Updated