Synergistic Sn-Induced Band Convergence in Mn-Doped p-Type PbTe Enables High Thermoelectric Performance

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Thermoelectric materials enable direct heat-to-electricity conversion but face challenges in optimizing the thermoelectric figure of merit (zT).
• Lead telluride (PbTe) is a promising thermoelectric material, yet its performance is limited by the coupled nature of electrical and thermal transport.

Purpose of the Study:

• To develop a synergistic co-doping strategy to simultaneously optimize electronic band structure and reduce lattice thermal conductivity in p-type PbTe.
• To investigate the effects of co-doping with manganese (Mn) and tin (Sn) on the thermoelectric properties of PbTe.

Main Methods:

• Synergistic co-doping of p-type PbTe with Mn and Sn.
• Microscopic and compositional analyses to confirm dopant incorporation and effects on carrier concentration.
• Measurement of Seebeck coefficient, electrical conductivity, and thermal conductivity to evaluate thermoelectric performance.

Main Results:

• Sn incorporation increased hole carrier concentration and Na dopant solubility.
• Co-doping with Mn and Sn enhanced valence band convergence, boosting the Seebeck coefficient.
• Multiscale lattice defects introduced by co-doping effectively scattered phonons, reducing lattice thermal conductivity to near the theoretical minimum (~0.5 W m⁻¹ K⁻¹).
• The Pb₀.₉₁₋ₓNa₀.₀₄Mn₀.₀₄SnₓTe system achieved a peak zT of ~2.2 at 823 K and a record room-temperature zT of ~0.4.

Conclusions:

• Mn and Sn co-doping is an effective strategy to simultaneously optimize band structure and suppress lattice thermal conductivity in PbTe.
• This approach leads to significant improvements in both peak and average thermoelectric performance.
• The achieved high thermoelectric performance, especially at room temperature, advances PbTe-based materials for practical waste-heat recovery applications.