Semi-coherent interfaces synergistically optimize thermoelectric performance in Pb-doped Bi_0.4Sb_1.6Te₃

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Nanoprecipitate engineering in Bi_2-xSb_xTe₃ materials enhances thermoelectric performance by reducing lattice thermal conductivity.
• Dense, incoherent interfaces from nanoprecipitates can increase carrier scattering, limiting performance gains.
• Optimizing interface structure is crucial for synergistic transport enhancement.

Purpose of the Study:

• To investigate the effect of lead (Pb) doping on the thermoelectric performance of Bi_0.4Sb_1.6Te₃.
• To explore how Pb doping induces semi-coherent interfaces and influences carrier and phonon transport.
• To demonstrate a strategy for synergistic transport optimization in thermoelectric materials.

Main Methods:

• Pb doping was introduced into Bi_0.4Sb_1.6Te₃ to form Sb nanoprecipitates.
• Characterization of interface structure (semi-coherent vs. incoherent) and its impact on carrier scattering.
• Measurement of thermoelectric properties, including carrier mobility, power factor, lattice thermal conductivity, and figure-of-merit (ZT).

Main Results:

• Pb doping promoted the formation of Sb nanoprecipitates with semi-coherent interfaces by lowering Sb vacancy formation energy.
• Semi-coherent interfaces suppressed carrier scattering, leading to high weighted mobility (544 cm² V^-1 s^-1) and power factor (48 μW cm^-1 K^-2).
• Sb nanoprecipitates effectively scattered phonons, achieving low lattice thermal conductivity (0.51 W m^-1 K^-1 at 460 K).
• The maximum figure-of-merit (ZT) increased from 0.81 to 1.06 at 460 K for Pb-doped Bi_0.4Sb_1.594Pb_0.006Te₃.
• A peak thermoelectric conversion efficiency of ~5.5% was achieved.

Conclusions:

• Introducing semi-coherent interfaces via Pb doping is an effective strategy to enhance thermoelectric performance in Bi_2-xSb_xTe₃-based materials.
• Synergistic optimization of carrier and phonon transport through controlled interface engineering leads to significant improvements.
• This approach offers a promising pathway for developing high-performance thermoelectric materials.