Rational Design Vacancies and Crystallographic Distortion via Stepwise Optimization Strategy Enables High...

Area of Science:

• Materials Science
• Solid State Physics
• Chemistry

Background:

• CuGaTe2 exhibits a high Seebeck coefficient but poor thermoelectric performance due to low carrier concentration and high thermal conductivity.
• Optimizing thermoelectric materials requires balancing electrical and thermal transport properties.

Purpose of the Study:

• To enhance the thermoelectric performance of CuGaTe2 through a combined approach of vacancy engineering and crystallographic distortion.
• To investigate the effects of Ga-vacancy doping and Ag/In substitution on the material's properties.

Main Methods:

• Density-functional-theory calculations were integrated with experimental synthesis and characterization.
• Controlled gallium (Ga)-vacancy doping was employed to increase hole concentration.
• Silver (Ag) and Indium (In) substitutions were introduced to induce mass/size disorder and soften chemical bonds.

Main Results:

• Ga-vacancy doping increased hole concentration while preserving carrier mobility.
• Ag and In substitutions significantly reduced lattice thermal conductivity from ~7.96 to ~2.35 W m⁻¹ K⁻¹.
• The optimized material, Cu0.85Ag0.15Ga0.965In0.025Te2, achieved a peak figure of merit of ~1.11 at 823 K, a 247% improvement over pristine CuGaTe2.

Conclusions:

• The synergistic coupling of vacancy engineering and lattice-distortion alloying is a powerful strategy for designing high-performance thermoelectric materials.
• This approach offers a viable route to overcome the limitations of traditional thermoelectric materials.