Abstract
Thermoelectric power generation is an energy conversion technology from heat to electric energy, which can be applied to waste heat power conversion. Among thermoelectric materials (TE), PbTe-PbSe-PbS quaternary alloys and composites are promising candidates for thermoelectric power generation applications in the mid-temperature operating range from 500 to ~850 K. Besides, the thermoelectric performance of quaternary alloys and composites is not fully optimized regarding its composition and synthesis process. In the quaternary system, PbTe-PbSe-PbS, it was found that PbS will form nanoprecipitation in the matrix of quaternary alloy for a small content of PbS (≤0.07), which reduces the lattice thermal conductivity. The power factor of PbTe-PbSe-PbS quaternary alloys can be significantly enhanced by using a band convergence in PbTe1−xSex. The band structure modifications, with the result of simultaneous PbS nanoprecipitation, give rise to a high Z T value of 2.3 at 800 K for (PbTe)0.95−x(PbSe)x(PbS)0.05. The chemical potential tuning by effective K-doping ( x = 0.02) and PbS substitution reveals a high power factor and low thermal conductivity, resulting in a comparatively high Z T value of 1.72 at 800 K. The combination of a high Seebeck coefficient and low thermal conductivity results in a very high Z T value of 1.52 at 700 K as n-type materials for low Cl-doped ( x = 0.0005) (PbTe0.93−xSe0.07Clx)0.93(PbS)0.07 composites. Therefore, this review presents the simultaneous emergence of effective chemical potential tuning, band convergence, and nanoprecipitation, giving rise to a significant enhancement of the thermoelectric performance of both p - and n -type PbTe-PbSe-PbS quaternary alloy and composite TE materials.
Highlights
Much effort has been devoted to searching for materials that can convert waste heat into electricity owing to the growing global demand for green energy
Effective thermoelectric materials are expected to have low thermal conductivity, κ, and electrical resistivity, ρ, and a high Seebeck coefficient, S, which is defined by the dimensionless thermoelectric figure-of-merit, ZT = S2 T/(ρκ)
In spite of high ZT values for Pb-based quaternary alloys, the thermoelectric performances of reported alloys are partially optimized in terms of the content of binary compounds and synthesis process [27,28,29]
Summary
Much effort has been devoted to searching for materials that can convert waste heat into electricity owing to the growing global demand for green energy. The thermoelectric performance in PbTe1−x Sex ternary alloys can be increased by nanostructuring, resulting in low lattice thermal conductivity. High ZT ≈ 2.2 at 800 K was obtained in p-type (PbTe)1−2x (PbSe)x (PbS)x quaternary alloys due to band engineering and phonon scattering from point defects [20,23,24]. The quaternary alloy system, PbTe-PbSe-PbS, is a promising candidate for use in thermometric power generation devices because alloy materials exhibit both n- and p-type properties with high thermoelectric performance [25]. This review briefly introduces the simultaneous emergence of band convergence, nanostructuring, and chemical potential tuning in PbTe-PbSe-PbS quaternary alloys and composites, which provides an extremely high thermoelectric figure-of-merit in p- and n-type materials
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