Nanostructures Boost the Thermoelectric Performance of PbS

Abstract

In situ nanostructuring in bulk thermoelectric materials through thermo-dynamic phase segregation has established itself as an effective paradigm for optimizing the performance of thermoelectric materials. In bulk PbTe small compositional variations create coherent and semicoherent nanometer sized precipitates embedded in a PbTe matrix, where they can impede phonon propagation at little or no expense to the electronic properties. In this paper the nanostructuring paradigm is for the first time extended to a bulk PbS based system, which despite obvious advantages of price and abundancy, so far has been largely disregarded in thermoelectric research due to inferior room temperature thermoelectric properties relative to the pristine fellow chalcogenides, PbSe and PbTe. Herein we report on the synthesis, microstructural morphology and thermoelectric properties of two phase (PbS)(1-x)(PbTe)(x)x = 0-0.16 samples. We have found that the addition of only a few percent PbTe to PbS results in a highly nanostructured material, where PbTe precipitates are coherently and semicoherently embedded in a PbS matrix. The present (PbS)(1-x)(PbTe)(x) nanostructured samples show substantial decreases in lattice thermal conductivity relative to pristine PbS, while the electronic properties are left largely unaltered. This in turn leads to a marked increase in the thermoelectric figure of merit. This study underlines the efficiency of the nanostructuring approach and strongly supports its generality and applicability to other material systems. We demonstrate that these PbS-based materials, which are made primarily from abundant Pb and S, outperform optimally n-type doped pristine PbTe above 770 K.

Visible-active photocatalytic behaviors observed in nanostructured lead chalcogenides PbX (X = S, Se, Te)

“…As reported of spectroscopic absorption measurements, band gaps are 0.32 eV, 0.28 eV and 0.41 eV for PbTe, PbSe and PbS, respectively, 25,26 and the optical transitions in these compounds are of direct type. 16 quantum-confinement effect more remarkable.…”

Unique Role of Refractory Ta Alloying in Enhancing the Figure of Merit of NbFeSb Thermoelectric Materials

“…Strategies for increasing zT have focused on the reduction of the lattice thermal conductivity by hierarchical microstructure, [3,4] nanostructuring [5,6] point defects, [7,8] and the enhancement of the power factor (PF = α 2 σ) by optimal doping and band engineering [9][10][11] as well as the employment of complex crystal structures that possess intrinsically low lattice thermal conductivity. [12][13][14][15][16] Half-Heusler (HH) alloys, with a valence electron count of 8 or 18, have been extensively studied as potential hightemperature TE materials due to their excellent electrical properties, mechanical properties, and high temperature stability.…”

Thermoelectric performance of tellurium-reduced quaternary p-type lead–chalcogenide composites

“…Recent studies 7-9 11 12 have improved PbTe thermoelectric performance significantly through tuning the electronic structure and/or nanostructuring of bulk materials. However, Te is rare in the Earth's crust, used in other applications 13 and is expensive hence the focus in the latest studies [14][15][16][17] trying to replace Te with Se or S. 18 19 Sulphur is amongst the 16 most abundant elements in the Earth's crust 13 and replacing Te, partially with S also provides a fascinating opportunity to form fine lamellar microstructure through spinodal decomposition, which appears in binary phase diagrams of the PbTe-PbS system. Lamellar patterns resembling a eutectic structure have been demonstrated for several thermoelectric materials 17 20-22 and thermal conductivity reduction has been reported, specifically for PbTe-PbS system, 14 …”