Enhanced Thermoelectric Performance in n-Type SrTiO₃/SiGe Composite

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Silicon germanium (SiGe) alloys are promising for high-temperature thermoelectric power generation, particularly in deep-space missions.
• Enhancing the dimensionless thermoelectric figure-of-merit (ZT) is crucial for broader civil applications of SiGe.

Purpose of the Study:

• To develop high-performance oxide/SiGe bulk composites for improved thermoelectric applications.
• To investigate the effect of incorporating La-Nb-doped SrTiO3 (La-Nb-STO) nanoparticles into a SiGe matrix on thermoelectric properties.

Main Methods:

• Fabrication of phosphorus (P)-doped SiGe via mechanical alloying (ball-milling).
• Preparation of La-Nb-STO powder through ball milling of hot-pressed, hydrothermally synthesized material.
• Hot-press sintering of mixed P-doped SiGe and La-Nb-STO powders to create bulk composites.

Main Results:

• A high ZT of 0.91 was achieved in n-type oxide/SiGe bulk composites at 1000 K.
• The addition of La-Nb-STO nanoparticles increased the power factor by optimizing electron concentration and mobility.
• The second phase (La-Nb-STO) reduced thermal conductivity due to enhanced phonon scattering at interfaces.

Conclusions:

• The developed oxide/SiGe composites demonstrate significantly improved thermoelectric performance compared to typical space mission materials and single-phase SiGe.
• The strategy of incorporating oxide nanoparticles offers a viable route for further enhancing the ZT of nanostructured SiGe and SrTiO3-based materials.