Lanthanide Contraction as a Design Factor for High-Performance Half-Heusler Thermoelectric Materials

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Solid solutions enhance thermoelectric performance but face challenges with alloy scattering, reducing thermal conductivity and carrier mobility.
• A key challenge is decoupling these opposing effects for optimal material design.

Purpose of the Study:

• To propose and validate a design strategy using lanthanide contraction to improve thermoelectric materials.
• To investigate the decoupling of thermal conductivity and carrier mobility in half-Heusler alloys.

Main Methods:

• Utilizing lanthanide contraction to select alloying atoms with significant mass fluctuation but minimal radius difference.
• Synthesizing and characterizing n-type (Zr,Hf)NiSn and p-type (Nb,Ta)FeSb half-Heusler solid solutions.
• Developing n-type (Zr,Hf)CoSb-based alloys incorporating lanthanide contraction.

Main Results:

• Demonstrated suppressed lattice thermal conductivity and maintained carrier mobility in typical half-Heusler alloys.
• Achieved high thermoelectric figure of merit (zT) of approximately 1.0 in n-type (Zr,Hf)CoSb-based alloys.
• Validated lanthanide contraction as a crucial design factor for enhancing thermoelectric properties.

Conclusions:

• Lanthanide contraction effectively decouples the trade-off between thermal conductivity and carrier mobility in thermoelectric alloys.
• (Zr,Hf)CoSb-based half-Heusler compounds show significant potential for practical thermoelectric applications.
• The proposed design strategy offers a new avenue for optimizing thermoelectric materials.