Engineer GeTe Thermoelectrics
Optimize operating-window performance and reliability, not an isolated peak zT.
Load evidence by task
- Read knowledge-base.md for GeTe phase, native defects, bands, phonons, and composition families.
- Read experimental-workflow.md before synthesis, computation, characterization, or optimization.
- Read devices-and-reliability.md before contact, barrier, leg, or module design.
- Activate
research-thermoelectric-semiconductors for general metrology and module theory.
Start from coupled constraints
Account for: acceptor-like Ge vacancies and typically excessive p-type carriers; composition-dependent rhombohedral-to-cubic evolution in the service range; multiple valence-band extrema coupled to distortion; and phase-dependent expansion, diffusion, Te-rich reactivity, and contact resistance.
Classify each intervention by its intended lever: vacancy/carrier control; Fermi-level tuning; band convergence; phase/distortion control; phonon scattering; mechanical/interface stability; or device compatibility. Predict final composition, phase/transition, Hall response, S/sigma/kappa, mechanics, and junction behavior. Include porosity, second phases, Lorenz-number choice, Te loss, and contact reaction as counter-hypotheses.
Execute stage gates
- Define hot/cold temperatures, atmosphere, cycles, target average performance, n-leg, and element constraints.
- Reproduce final composition, density, phase, carrier response, and full-window transport in independent baseline batches.
- Separate vacancy compensation, band/phase engineering, phonon scattering, and thermal history where possible.
- Close Ge/Te mass and phase balance; map segregation, precipitates, and phase fractions.
- Measure heating/cooling
S(T), sigma(T), field-dependent Hall response, diffusivity, heat capacity, density, and kappa(T) with uncertainty through transition anomalies.
- Test mechanisms using independent defect, band, structural, or phonon evidence and matched-carrier/density controls.
- Screen barrier/electrode/bond coupons for reaction, contact resistivity, strength, CTE, and aging.
- Validate legs/modules with temperature-dependent models, actual junction temperatures, heat input, full load curves, repeat builds, and post-mortem analysis.
Treat DFT as prediction or mechanistic support, not proof of experimental defect population, solubility, phase purity, or service stability. Treat one-band Hall and constant heat-capacity/Lorenz approximations with sensitivity analysis near multiband and phase-transition regimes.
Diagnose coupled signatures
- Larger
|S| with sharply lower mobility: test overcompensation, ionized-impurity scattering, precipitates, and porosity.
- Lower inferred lattice
kappa without structural evidence: vary Lorenz model, heat capacity, density, radiation, and bipolar assumptions.
- Thermal hysteresis or irreversible transport: pair calorimetry/in-situ diffraction with composition and cycling.
- Strong coupon performance but weak module: separate bulk, contact, electrode, bond, thermal spreading, and p/n mismatch losses.
- Resistance growth near hot side: section the junction before bulk averaging hides the reaction layer.
1---2name: engineer-gete-thermoelectrics3description: Engineer and audit GeTe-based thermoelectric materials and devices across defect chemistry, carrier concentration, band and phase engineering, phonon scattering, synthesis, temperature-dependent transport, contacts, diffusion barriers, legs, modules, and reliability; use when GeTe composition, Ge vacancies, rhombohedral-cubic transition, band convergence, average zT, junctions, or mid-temperature module performance is central.4---5
6# Engineer GeTe Thermoelectrics
7
8Optimize operating-window performance and reliability, not an isolated peak `zT`.
9
10## Load evidence by task
11
12- Read [knowledge-base.md](references/knowledge-base.md) for GeTe phase, native defects, bands, phonons, and composition families.
13- Read [experimental-workflow.md](references/experimental-workflow.md) before synthesis, computation, characterization, or optimization.
14- Read [devices-and-reliability.md](references/devices-and-reliability.md) before contact, barrier, leg, or module design.
15- Activate `research-thermoelectric-semiconductors` for general metrology and module theory.
16
17## Start from coupled constraints
18
19Account for: acceptor-like Ge vacancies and typically excessive p-type carriers; composition-dependent rhombohedral-to-cubic evolution in the service range; multiple valence-band extrema coupled to distortion; and phase-dependent expansion, diffusion, Te-rich reactivity, and contact resistance.
20
21Classify each intervention by its intended lever: vacancy/carrier control; Fermi-level tuning; band convergence; phase/distortion control; phonon scattering; mechanical/interface stability; or device compatibility. Predict final composition, phase/transition, Hall response, `S/sigma/kappa`, mechanics, and junction behavior. Include porosity, second phases, Lorenz-number choice, Te loss, and contact reaction as counter-hypotheses.
22
23## Execute stage gates
24
251. Define hot/cold temperatures, atmosphere, cycles, target average performance, n-leg, and element constraints.
262. Reproduce final composition, density, phase, carrier response, and full-window transport in independent baseline batches.
273. Separate vacancy compensation, band/phase engineering, phonon scattering, and thermal history where possible.
284. Close Ge/Te mass and phase balance; map segregation, precipitates, and phase fractions.
295. Measure heating/cooling `S(T)`, `sigma(T)`, field-dependent Hall response, diffusivity, heat capacity, density, and `kappa(T)` with uncertainty through transition anomalies.
306. Test mechanisms using independent defect, band, structural, or phonon evidence and matched-carrier/density controls.
317. Screen barrier/electrode/bond coupons for reaction, contact resistivity, strength, CTE, and aging.
328. Validate legs/modules with temperature-dependent models, actual junction temperatures, heat input, full load curves, repeat builds, and post-mortem analysis.
33
34Treat DFT as prediction or mechanistic support, not proof of experimental defect population, solubility, phase purity, or service stability. Treat one-band Hall and constant heat-capacity/Lorenz approximations with sensitivity analysis near multiband and phase-transition regimes.
35
36## Diagnose coupled signatures
37
38- Larger `|S|` with sharply lower mobility: test overcompensation, ionized-impurity scattering, precipitates, and porosity.
39- Lower inferred lattice `kappa` without structural evidence: vary Lorenz model, heat capacity, density, radiation, and bipolar assumptions.
40- Thermal hysteresis or irreversible transport: pair calorimetry/in-situ diffraction with composition and cycling.
41- Strong coupon performance but weak module: separate bulk, contact, electrode, bond, thermal spreading, and p/n mismatch losses.
42- Resistance growth near hot side: section the junction before bulk averaging hides the reaction layer.
gabrielmoreira