High Thermoelectric Performance Achieved in Nb0.8Ti0.2FeSb via PbI2‐Driven Multiscale Defect Engineering

Why It Matters

The breakthrough simultaneously solves the thermal‑conductivity bottleneck and mechanical weakness of high‑temperature thermoelectrics, accelerating their viability for waste‑heat recovery and power‑generation systems.

Key Takeaways

• PbI2 creates hierarchical defects reducing lattice thermal conductivity.
• Lattice thermal conductivity drops 32% to 3.34 W/m·K at 973 K.
• Electrical conductivity improves, yielding power factor 52.7 µW/cm·K².
• Figure of merit zT reaches ~1, a notable thermoelectric gain.
• Mechanical strength increases 38% despite added porosity.

Pulse Analysis

Half‑Heusler compounds such as NbFeSb are prized for their high electrical conductivity and structural robustness, yet their commercial adoption has been hampered by intrinsically high lattice thermal conductivity. Traditional approaches—grain‑size reduction, alloying, or nanoinclusions—often require complex, low‑temperature processing that compromises mechanical integrity. By leveraging a sublimable precursor, PbI2, researchers have demonstrated a scalable route to embed a spectrum of defects, from nanoscale PbI2 residues to micron‑scale pores and Fe vacancies, all formed in‑situ during high‑temperature sintering. This multiscale architecture disrupts phonon transport across the entire frequency range, delivering a substantial 32% reduction in lattice thermal conductivity without sacrificing carrier mobility.

The defect hierarchy also plays a pivotal role in electronic transport. The presence of PbI2 nanophases and the softening effect of Fe vacancies lower the grain‑boundary potential barrier, facilitating hole movement and increasing carrier concentration. Consequently, the electrical conductivity rises, and the power factor reaches 52.7 µW cm⁻¹ K⁻², propelling the thermoelectric figure of merit (zT) to around 1—a benchmark for practical waste‑heat conversion. Importantly, the second‑phase strengthening from residual PbI2 offsets the weakening typically associated with porosity, yielding a 38% boost in compressive strength and a microhardness of 950 HV, thereby preserving the material’s load‑bearing capability.

For the broader energy sector, this advancement signals a viable pathway to high‑performance, mechanically resilient thermoelectric modules capable of operating at temperatures near 1000 K. The ability to integrate such materials into automotive exhaust systems, industrial furnaces, or concentrated solar power plants could unlock significant efficiency gains and reduce carbon footprints. Moreover, the PbI2‑driven strategy is adaptable to other half‑Heusler families, suggesting a versatile platform for next‑generation thermoelectric devices that balance power output, durability, and manufacturing practicality.