Nano- and Microstructure Engineering: An Effective Method for Creating High Efficiency Magnesium Silicide Based...

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Growing CO2 emissions and fossil fuel depletion necessitate sustainable energy solutions.
• The transportation sector requires efficient waste heat recovery to meet environmental regulations.
• Thermoelectric materials offer a potential solution if their energy conversion efficiency can be improved.

Purpose of the Study:

• To investigate the high-temperature thermoelectric properties of bismuth-doped magnesium silicide-tin (Mg2(Si,Sn)).
• To optimize thermoelectric performance through band convergence and microstructure engineering.
• To assess the potential of these materials for waste heat recovery applications.

Main Methods:

• Synthesis of Mg2Si1-x-SnxBiy samples with specific compositions (x ≥ 0.6, y ≥ 0.03).
• Characterization of thermoelectric properties, including electrical conductivity, Seebeck coefficient, and thermal conductivity.
• Microstructure analysis using ball mill processing to engineer grain boundaries and phonon scattering.

Main Results:

• Achieved high electrical conductivities (~1000 Ω⁻¹ cm⁻¹) and Seebeck coefficients (~-200 μV K⁻¹) at 773 K.
• Obtained low thermal conductivity (< 2.5 W m⁻¹ K⁻¹) due to efficient phonon scattering.
• Reached a peak thermoelectric figure of merit (zT) of 1.4 at 773 K, with an average zT of 0.9 from 400-773 K.
• Demonstrated reproducible and thermally stable transport properties.

Conclusions:

• Bismuth-doped Mg2(Si,Sn) exhibits excellent high-temperature thermoelectric properties.
• Band convergence and microstructure engineering are key to enhancing performance.
• These materials show significant potential for efficient waste heat recovery and reducing CO2 emissions in the transportation sector.