Developing a Multiband Electronic Band Structure Model and Predictive Maps for Bismuth-Rich Mg₃(Sb_1-Bi)₂...

Area of Science:

• Materials Science
• Solid State Physics
• Thermoelectrics

Background:

• Bismuth-rich Mg3(Sb1-xBix)2 alloys (x=0.5-0.8) show excellent thermoelectric performance near room temperature.
• This performance is linked to a complex electronic band structure (EBS) with near-degenerate bands.
• Understanding the temperature dynamics of EBS is crucial for optimizing thermoelectric materials.

Purpose of the Study:

• To investigate the temperature dynamics of the electronic band structure (EBS) in Mg3Sb0.6Bi1.4 (x=0.7) with varying tellurium doping concentrations.
• To estimate key EBS parameters and thermal conductivity (κ).
• To generate predictive 3D maps of the thermoelectric figure of merit (zT) as a function of doping and temperature.

Main Methods:

• Synthesis of Mg3Sb0.6Bi1.4 compositions with varying tellurium doping.
• Estimation of electronic band structure parameters (effective mass, deformation potential, interband separation, band gap) using a refinement approach.
• Measurement of thermal conductivity (κ).
• Generation of 3D maps of zT based on EBS and κ data.

Main Results:

• Interband separation was found to be dependent on both temperature and doping concentration.
• Predictive 3D maps revealed a broad peak region for zT, indicating robustness to doping variations.
• The study provides detailed EBS information and fundamental insights into the thermoelectric properties of Mg3Sb0.6Bi1.4.

Conclusions:

• The temperature dynamics of EBS significantly influence thermoelectric performance in Mg3(Sb1-xBix)2 alloys.
• The observed broad zT peak explains the material's high performance and tolerance to doping inhomogeneities.
• The developed methodology can be applied to optimize other Mg3(Sb1-xBix)2 compositions and thermoelectric materials.