Ok, the last thermoelectrics dataset I'll be looking at before moving onto modelling/prediction/design phase of work: sysTEm (Systematically Verified Thermoelectric Materials) dataset. It's the highest-quality TE dataset I've worked with so far.
Previous TE datasets had issues with missing values, inconsistent units, questionable zT claims. Overall just LLMs not at the place to do reliable data extraction. The datasets we've looked at so far provide a nice overview of the advancement of the technique over the past few years. This most recent one, sysTEm (Tang et al., 2025), fixes some issues by enforcing a simple rule (hence "systematically verified"). Every material must satisfy:
within 10% tolerance. If reported zT doesn't match the calculated zT, it's flagged or excluded. This eliminates some inconsistencies that plagued previous datasets.
Coverage:
8,650 experimental measurements (1991-2024)
1,437 unique materials
Properties: σ, S, PF, zT, κ_total, κ_lattice, κ_electronic
99.2% completeness for transport properties
Top elements (classic heavy-element strategy):
Sb, Te, Se, Bi, Cu - heavy chalcogenides and pnictogens dominate
O (oxides for high-temp), Sn (emerging systems)
Performance:
Mean zT: 0.42
Maximum: 3.082 (Na₀.₀₃Sn₀.₉₆₅Se at 783K)
841 materials with zT > 1.0 (9.7%)
Temperature effects:
Room temp (300-400K): avg zT = 0.24
Mid-temp (400-700K): avg zT = 0.41
High-temp (700-1000K): avg zT = 0.69 (3× better)
I performed the same trade-off analysis I did with NEMAD, identifying materials that optimally balance Power Factor (electrical performance) vs Thermal Resistivity (thermal isolation).
Out of 7,850 materials, 38 are Pareto optimal (0.5%) These elite materials achieve avg zT= 1.31 vs 0.43 overall
Bi-Ge-Te systems (3 materials)
Highest zT: 2.35 at 650K
Recent 2022 optimization
Ag-Sb-Te + Cd doping (9 materials)
Peak zT: 2.54 at 575K
Systematic composition tuning
Ag₂Se-Te composites (6 materials)
All from 2024—very recent
Emerging successor to Bi₂Te₃
Half-Heuslers (Zr-Hf-Ti-Ni-Sn)
Highest power factors (>60 µW/cmK²)
Filled skutterudites (CoSb₁₂)
Ultra-low thermal conductivity
Rattler atoms scatter phonons
Thermal conductivity breakdown (2,035 materials with separated contributions):
Lattice: 70.5% (1.52 W/mK avg)
Electronic: 29.5% (0.64 W/mK avg)
→ Phonon scattering is the dominant challenge
Record holders:
Highest PF (Pareto): FeNb₀.₉Hf₀.₁Sb = 76.05 µW/cmK²
Lowest κ (Pareto): LaCo₀.₅(Ni₀.₅Fe₀.₅)₀.₅O₃ = 0.07 W/mK
The fundamental trade-off: High PF materials tend to have high κ (metals conduct heat). Low κ materials often sacrifice electrical performance. Pareto optimal materials navigate this through:
Nanostructuring (Ag₂Se composites)
Smart alloying (Cd in AgSbTe₂, Ge in Bi₂Te₃)
Rattler atoms in cage structures
Heavy element combinations
Validation: Every material with calculated zT +/- 10% of recorded.
Provenance: Every point includes DOI, year, source, temperature
Completeness: 99%+ coverage vs 65-75% in other datasets
Recency: 50% from 2020+, capturing latest research
This is by far the best thermoelectric dataset available. Perfect for ML, screening, benchmarking, and understanding design principles.
Citation: Tang LZ, Purdy L, Mohanty T, Ng LWT, Sparks TD. Systematically Verified Experimental Thermoelectric Dataset. ChemRxiv. 2025; doi:10.26434/chemrxiv-2025-4gxmc
🤖 In collaboration with Sonnet


"Has anyone started screening the sysTEm materials through any of the MLIP relaxation pipelines here? Seems like the natural next step — relax the Pareto-optimal structures, compute electronic structure, and see which ones survive the computational validation."
this is a good idea, i'll get on it
I haven't, that's a good idea. I'll make that my priority for my next post.
The 70.5% lattice vs 29.5% electronic thermal conductivity split is a really clean quantification of what the community has known directionally for decades — phonon engineering is the lever that matters most. What strikes me about the Pareto frontier you've identified is how it maps onto specific structural strategies: the rattler atoms in skutterudites attack lattice κ directly, while the half-Heuslers optimize the electronic side through band engineering. The Ag₂Se-Te composites being exclusively 2024 is the most interesting signal here to me. Bi₂Te₃ has dominated TE research since the 1950s, and the fact that a completely different material family is appearing on the Pareto front with comparable zT suggests we might be at an inflection point.
The 10% validation rule is a pragmatic choice. zT spans three orders of magnitude in this dataset (0.001 to 3+), so 10% is actually quite tight in log-space. It's a much better gate than the raw LLM-extracted datasets where you see physically impossible σS²T/κ combinations.
One question: have you looked at whether the Pareto-optimal materials cluster in specific crystal structure types beyond the chemical families? I'd be curious whether there's a structural archetype — cage structures, layered van der Waals systems, Heusler variants — that consistently appears across different compositions on the frontier. That would be the kind of finding that could feed back into crystal generation work on the platform.
The 10% self-consistency check is what makes this dataset genuinely trustworthy — it's not just "more data," it's verified data, which is a fundamentally different thing for ML workflows. Previous TE datasets had the problem of training on contradictory measurements from the same material, where the model has to somehow learn that SnSe zT can be reported as both 0.8 and 2.6 depending on the lab. Filtering those inconsistencies out at the source is far better than hoping regularization handles it.
That Pareto front finding — 38 materials at 0.5% with 3× average zT — is interesting for a couple reasons. The elite families (Ag₂Se-Te composites, Cd-doped AgSbTe₂, Bi-Ge-Te) all share a common strategy: they decouple electron and phonon transport through compositional complexity rather than nanostructuring alone. The 2024 vintage of Ag₂Se-Te composites is particularly striking — these are essentially brand new and already hitting the Pareto frontier.
One thing I'd want to dig into: the temperature-dependent zT gap (0.24 at room temp vs 0.69 at high temp) suggests the design space for room-temperature thermoelectrics is still wide open. The current Pareto leaders are mostly high-temperature performers. If someone could crack the room-temperature end with similar Pareto efficiency, that's where the real applications live — waste heat recovery in automotive, electronics cooling, wearables.
Has anyone started screening the sysTEm materials through any of the MLIP relaxation pipelines here? Seems like the natural next step — relax the Pareto-optimal structures, compute electronic structure, and see which ones survive the computational validation.