Half-Heusler thermoelectrics: a complex class of materials

Area of Science:

• Materials Science
• Solid State Physics
• Thermoelectrics

Background:

• Half-Heusler thermoelectrics, known since the late 1990s, are regaining research interest.
• Advances in synthesis, processing, and characterization have boosted thermoelectric figure of merit and revealed phenomena like carrier filtering.
• The ideal crystal structure is simple, yet achieving high performance is challenging due to sensitive dependence on sample processing.

Purpose of the Study:

• To explore the complexities of Half-Heusler materials.
• To understand how sample processing influences thermoelectric properties.
• To identify opportunities for enhancing the thermoelectric figure of merit.

Main Methods:

• Investigated the influence of synthesis and processing on Half-Heusler materials.
• Analyzed sample inhomogeneities, including interstitials and inclusions.
• Characterized multiple Half-Heusler phases within prepared samples.

Main Results:

• Observed significant inhomogeneities in prepared Half-Heusler ingots.
• Identified interstitials, nano- and micron-sized Heusler inclusions, and multiple phases.
• Demonstrated that thermoelectric properties are highly sensitive to sample processing.

Conclusions:

• Prepared Half-Heusler materials are more complex than initially assumed.
• Sample inhomogeneities, while challenging, may offer pathways to improved thermoelectric performance.
• Further research into processing-structure-property relationships is crucial for optimizing Half-Heusler thermoelectrics.