Design Principles and Experimental Evidence for Semiconducting Heusler Thermoelectrics by Vacancy‐Filling

Why It Matters

By independently tuning electrical conductivity and lattice heat flow, the vacancy‑filling approach accelerates the creation of efficient thermoelectrics for waste‑heat recovery and renewable energy applications.

Key Takeaways

• Vacancy filling creates bandgap in Heusler alloys
• Partial 4d site occupancy lowers lattice thermal conductivity
• TiFe0.5Co0.67Sb achieves ZT 0.53 at 973 K
• Strategy decouples electronic and thermal transport
• Generalizable design rule for semiconducting Heuslers

Pulse Analysis

Thermoelectric technology hinges on the delicate balance between electrical conductivity, Seebeck coefficient, and lattice thermal conductivity. Traditional Heusler alloys, while structurally robust, often suffer from high phonon transport that suppresses overall efficiency. Recent advances in materials engineering have turned to atomic‑scale modifications, such as vacancy filling, to break this coupling and open new pathways for performance gains.

The vacancy‑filling method targets the 4d crystallographic sites, inserting atoms that reshape the electronic band structure. By establishing a clear separation between fully occupied t2g orbitals and empty eg states, a modest bandgap emerges, enabling semiconducting behavior without sacrificing carrier mobility. In the TiFeₓCoᵧSb series, the stoichiometric relationship 2x+3y=3 ensures precise control over site occupancy, leading to p‑type conduction and a lattice thermal conductivity as low as 2.77 W·m⁻¹·K⁻¹ at ambient conditions. The optimal composition, TiFe₀.5Co₀.67Sb, pushes the figure of merit to 0.53 at 973 K, a notable achievement for bulk Heusler compounds.

Beyond the immediate performance metrics, this strategy offers a scalable blueprint for designing next‑generation thermoelectrics. Decoupling electronic and thermal transport allows researchers to tailor each property independently, accelerating the discovery of materials that can harvest waste heat from industrial processes, automotive exhaust, and power‑plant flue gases. As the global push for energy efficiency intensifies, vacancy‑filled Heusler alloys could become a cornerstone of commercial thermoelectric modules, bridging the gap between laboratory breakthroughs and market‑ready solutions.