Spatially Homogeneous Mg₃(Sb, Bi)₂ With Suppressed Parasitic Transport Enables Ultrahigh Thermoelectric Performance

Area of Science:

• Materials Science
• Solid State Physics
• Chemistry

Background:

• Chemical inhomogeneity is common in thermoelectric materials, often linked to interface scattering and composition fluctuations.
• The impact of spatial connectivity in chemical inhomogeneity on thermoelectric performance is not well understood.

Purpose of the Study:

• To investigate the role of spatial connectivity of chemical inhomogeneity in thermoelectric materials.
• To optimize thermoelectric performance in Mg3(Sb, Bi)2 by controlling chemical inhomogeneity.

Main Methods:

• Utilized cyclic pressure sintering to modify the spatial connectivity of Bi-related chemical inhomogeneity in Mg3(Sb, Bi)2.
• Analyzed the effects of altered inhomogeneity on thermoelectric transport properties (Seebeck coefficient, thermal conductivity) and figure of merit (zT).

Main Results:

• Discovered that spatially connected inhomogeneity forms parasitic transport pathways, degrading thermoelectric performance.
• Achieved a peak zT of ~2.08 at 673 K and an average zT of ~1.58 over 323-723 K through cyclic pressure sintering.
• Demonstrated a single-leg device with a conversion efficiency of ~12.1% (ΔT = 410 K).

Conclusions:

• Spatial connectivity of chemical inhomogeneity is a critical factor governing thermoelectric transport.
• Cyclic pressure sintering offers a viable strategy to disrupt detrimental percolative networks and enhance thermoelectric performance.
• The findings provide a general approach for optimizing thermoelectric materials by managing heterogeneity.