Favorable Contact with Low Interfacial Resistance for n-Type TiCoSb-Based Thermoelectric Devices

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Half-Heusler (HH) thermoelectric (TE) materials show promise for energy harvesting.
• Practical application of HH TE devices is hindered by challenges in fabricating stable, low-interfacial-resistance electrical contacts.
• Previous attempts using Fe, Co, and Ti as contacts for TiCoSb-based TE materials faced issues like poor bonding, high resistance, and diffusion.

Purpose of the Study:

• To explore a stable contact material with low interfacial resistance for n-type TiCoSb-based thermoelectric materials.
• To demonstrate the effectiveness of a highly doped semiconductor (HDS) contact for improving TE device performance.

Main Methods:

• Fabrication of Ti_0.85Nb_0.15CoSb_0.96Bi_0.04 thermoelectric material using spark plasma sintering.
• Testing of various metal contacts (Fe, Co, Ti) and a highly doped semiconductor (HDS) contact (Ti_0.7Nb_0.3CoSb).
• Characterization of interfacial properties, electronic transport, and device output power.

Main Results:

• Ti metal contact showed high electrical resistance (~300 mΩ) due to diffusion and a high potential barrier.
• The HDS contact (Ti_0.7Nb_0.3CoSb) exhibited excellent atomic bonding, crystal structure match, and stability with the TE material.
• The TE leg with the HDS contact achieved superior electronic transport, low interface resistance (~15 mΩ), and a maximum output power of 30.7 mW at ΔT = 451 K.

Conclusions:

• Highly doped semiconductor (HDS) materials are effective as contacts for half-Heusler thermoelectric materials.
• Using HDS contacts with the same HH TE material ensures atomic bonding, crystal structure compatibility, and thermal stability.
• This approach significantly reduces interface resistance and enhances the overall performance and thermal stability of thermoelectric devices.