Interpreting the Combustion Process for High-Performance ZrNiSn Thermoelectric Materials

Area of Science:

• Materials Science
• Solid State Physics
• Thermoelectrics

Background:

• Half-Heusler alloys like ZrNiSn are promising for mid-to-high temperature power generation.
• Current synthesis methods for these alloys are time-consuming and energy-intensive.
• Optimizing thermoelectric properties requires efficient and scalable fabrication techniques.

Purpose of the Study:

• To develop a rapid and cost-effective synthesis route for single-phase ZrNiSn bulk materials.
• To investigate the thermodynamic and kinetic aspects of the novel synthesis process.
• To evaluate the thermoelectric performance of the synthesized materials.

Main Methods:

• Combined self-propagating high-temperature synthesis (SHS) with spark plasma sintering (SPS) for ZrNiSn fabrication.
• Analyzed thermodynamic and kinetic processes of the ternary alloy formation.
• Characterized the microstructure and thermoelectric properties of the synthesized ZrNiSn$_{1-x}$Sb$_{x}$ alloys.

Main Results:

• Achieved single-phase ZrNiSn in under an hour, drastically reducing synthesis time from days.
• Identified a unique series of SHS reactions and mass transfers leading to ternary phase formation.
• Observed Ni interstitials enhancing electrical conductivity and reducing thermal conductivity.
• Attained a maximum thermoelectric figure of merit (ZT) of 0.7 at 870 K for SHS + SPS processed ZrNiSn$_{1-x}$Sb$_{x}$.

Conclusions:

• The SHS + SPS method offers a fast and low-cost pathway for fabricating half-Heusler thermoelectric materials.
• The novel synthesis approach enhances thermoelectric properties through microstructural modifications.
• This work presents a new avenue for efficient production of advanced thermoelectric materials.