Optimized electronic properties and nano-structural features for securing high thermoelectric performance in doped...

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Thermoelectric (TE) materials convert heat to electricity, with PbTe-based materials being highly effective but toxic.
• Lead-free alternatives are crucial for sustainable TE applications.
• Germanium telluride (GeTe) shows promise but requires optimization for enhanced performance.

Purpose of the Study:

• To discover and optimize lead-free thermoelectric materials based on GeTe.
• To enhance the thermoelectric performance of GeTe by co-doping with Bi, Zn, and In.
• To investigate the microstructural contributions to improved thermoelectric properties.

Main Methods:

• Co-doping of GeTe with Bi, Zn, and In.
• Systematic tuning of doping concentrations to optimize thermoelectric properties.
• Characterization using scanning transmission electron microscopy (STEM) to analyze microstructure.
• Evaluation of thermoelectric performance through figure of merit (zT) measurements.

Main Results:

• Bi doping enhanced performance by tuning electronic properties and reducing thermal conductivity.
• Zn doping maintained a high power factor and further reduced thermal conductivity.
• In doping in (Ge$_{0.97}$Zn$_{0.02}$In$_{0.01}$Te)$_{0.97}$(Bi$_{2}$Te$_{3}$)$_{0.03}$ significantly lowered thermal conductivity.
• STEM revealed nano-twinning, defect layers, and dislocation bands contributing to suppressed lattice thermal conductivity.

Conclusions:

• Co-doping GeTe with Bi, Zn, and In creates a high-performance lead-free thermoelectric material.
• The optimized composition (Ge$_{0.97}$Zn$_{0.02}$In$_{0.01}$Te)$_{0.97}$(Bi$_{2}$Te$_{3}$)$_{0.03}$ achieved a peak zT of 2.06.
• This material represents a significant advancement in lead-free thermoelectric technology.