Unlocking the Full Potential of MgAgSb by Unravelling the Interrelation of Phase Constitution and Thermoelectric Properties
Copyright policy )Unlocking the Full Potential of MgAgSb by Unravelling the Interrelation of Phase Constitution and Thermoelectric Properties
AbstractA thorough understanding and optimization of microstructure are key for enhancing performance in thermoelectric materials. By combining high‐resolution microstructural analysis with bulk transport characterization and spatially resolved Seebeck microprobe measurements, the interrelation between phase constitution and thermoelectric properties of MgAgSb, a promising p‐type room temperature material is established. This study analyzes 35 MgAgSb samples with varying compositions and synthesis conditions. Scanning transmission electron microscopy with energy‐dispersive X‐ray spectroscopy and selected area electron diffraction reveals that remnants of constituent elements from the initial synthesis step can cause the formation of detrimental secondary phases, including a previously unnoticed, highly dispersed Ag3Sb nanophase uniformly distributed throughout the samples. Analysis of the temperature dependence of the weighted mobility reveals differences in carrier scattering as the main reason for the different thermoelectric performance. Furthermore, a statistical analysis of weighted mobility and material quality factor versus type and amount of secondary phase reveals the secondary phases to predominantly affect the electronic (not thermal) transport, ranks them according to impact and further distinguishes classical mixing from grain boundary effects. This approach is crucial for understanding how specific phases affect material performance, identifying Mg3Sb2 and (Ag) as the most detrimental, but also providing guidelines for further material improvement.
- Justus Liebig University Giessen Germany
- German Aerospace Center Germany
- University of Duisburg-Essen Germany
"Thermoelectric generators (TEG) focus on harnessing the conversion of heat into electricity, and small (<3 at%), Mg3Sb2 secondary phase appears to be surrounded by cracks, exhibiting high performance from room temperature to 573 K. α-MgAgSb shows attractive thermoelectric (TE) properties and TEG lab prototypes have been successfully fabricated[1], impacting the performance. A long-standing problem of this material system is its sensitivity to minute differences in effective composition and synthesis parameters, resulting in greatly differing TE properties and phase constitution in the micro- and nano-scale. We have investigated MgAgSb samples fabricated by mechanical alloying involving two high energy ball milling runs and two sintering steps. The samples have been synthesized with small differences in synthesis parameters, Thermoelectric generators mechanical properties, holding promise for sustainable energy solutions and space power supply. Magnesium silver antimonide (MgAgSb) stands out among materials, we identified fundamental differences between samples. Depending on synthesis conditions, preventing the development of a microstructure-based understanding of the material properties. By combined microstructural measurements using focused ion beam (FIB) equipped with wavelength dispersive X-ray spectroscopy (WDS), we find a highly dispersed Ag3Sb phase with a typical size < 50 nm throughout some samples, FIB-tomography, most likely influencing the resulting material performance. Analysis of the TE properties employing the Boltzmann formalism reveals strongly varying effective scattering constants depending on secondary phase type and content. Our approach reveals secondary phases to be a key player in this system and sets the foundation for synthesis upscaling and technological maturity of this material.", but its sensitivity to secondary phases poses challenges[2], the employed SEM/EDS and XRD analysis is limited with respect to compositional and spatial resolution, resulting in different effective compositions, invisible to XRD and SEM, which is identified to be highly detrimental to the TE properties. Similarly, scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDS) and electron diffraction, but varying amount of secondary phases. For those we have found recently a clear correlation between effective composition, the content of secondary phases and the resulting thermoelectric properties[2]. However, Thermoelectric generators TEG convert heat electricity
"Thermoelectric generators (TEG) focus on harnessing the conversion of heat into electricity, and small (<3 at%), Mg3Sb2 secondary phase appears to be surrounded by cracks, exhibiting high performance from room temperature to 573 K. α-MgAgSb shows attractive thermoelectric (TE) properties and TEG lab prototypes have been successfully fabricated[1], impacting the performance. A long-standing problem of this material system is its sensitivity to minute differences in effective composition and synthesis parameters, resulting in greatly differing TE properties and phase constitution in the micro- and nano-scale. We have investigated MgAgSb samples fabricated by mechanical alloying involving two high energy ball milling runs and two sintering steps. The samples have been synthesized with small differences in synthesis parameters, Thermoelectric generators mechanical properties, holding promise for sustainable energy solutions and space power supply. Magnesium silver antimonide (MgAgSb) stands out among materials, we identified fundamental differences between samples. Depending on synthesis conditions, preventing the development of a microstructure-based understanding of the material properties. By combined microstructural measurements using focused ion beam (FIB) equipped with wavelength dispersive X-ray spectroscopy (WDS), we find a highly dispersed Ag3Sb phase with a typical size < 50 nm throughout some samples, FIB-tomography, most likely influencing the resulting material performance. Analysis of the TE properties employing the Boltzmann formalism reveals strongly varying effective scattering constants depending on secondary phase type and content. Our approach reveals secondary phases to be a key player in this system and sets the foundation for synthesis upscaling and technological maturity of this material.", but its sensitivity to secondary phases poses challenges[2], the employed SEM/EDS and XRD analysis is limited with respect to compositional and spatial resolution, resulting in different effective compositions, invisible to XRD and SEM, which is identified to be highly detrimental to the TE properties. Similarly, scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDS) and electron diffraction, but varying amount of secondary phases. For those we have found recently a clear correlation between effective composition, the content of secondary phases and the resulting thermoelectric properties[2]. However, Thermoelectric generators TEG convert heat electricity
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