Extrinsic doping of the half-Heusler compounds

Area of Science:

• Materials Science
• Solid State Physics
• Computational Chemistry

Background:

• Optimizing thermoelectric materials requires precise control over p-type and n-type doping.
• Half-Heusler compounds are promising thermoelectric materials, but understanding their defect chemistry is crucial for performance enhancement.

Purpose of the Study:

• To provide a detailed understanding of defect thermochemistry in n-type TiNiSn and p-type TiCoSb.
• To identify intrinsic and extrinsic defects influencing carrier concentration in these materials.
• To explore novel doping strategies for improving thermoelectric power factors.

Main Methods:

• First-principles calculations of formation energies for intrinsic and extrinsic defects.
• Analysis of defect thermochemistry in state-of-the-art TiNiSn and TiCoSb.
• Utilizing online repositories to streamline computational workload.

Main Results:

• Ni- and Ti-interstitial defects significantly impact carrier concentration in TiNiSn.
• Extrinsic antimony (Sb) doping enhances carrier concentration in TiNiSn, consistent with experimental findings.
• Identified ScTi, FeCo, and SnSb as potential p-type dopants for TiCoSb, suggesting doping is possible on all lattice sites.

Conclusions:

• Defect thermochemistry provides critical insights into doping control in half-Heusler thermoelectrics.
• Novel doping strategies, including on multiple lattice sites, can be explored for TiCoSb.
• Computational methods, aided by online repositories, are effective for understanding and optimizing thermoelectric materials.