Lattice Dislocations Enhancing Thermoelectric PbTe in Addition to Band Convergence

Abstract

Phonon scattering by nanostructures and point defects has become the primary strategy for minimizing the lattice thermal conductivity (κ ) in thermoelectric materials. However, these scatterers are only effective at the extremes of the phonon spectrum. Recently, it has been demonstrated that dislocations are effective at scattering the remaining mid-frequency phonons as well. In this work, by varying the concentration of Na in Pb Eu Te, it has been determined that the dominant microstructural features are point defects, lattice dislocations, and nanostructure interfaces. This study reveals that dense lattice dislocations (≈4 × 10 cm ) are particularly effective at reducing κ . When the dislocation concentration is maximized, one of the lowest κ values reported for PbTe is achieved. Furthermore, due to the band convergence of the alloyed 3% mol. EuTe the electronic performance is enhanced, and a high thermoelectric figure of merit, zT, of ≈2.2 is achieved. This work not only demonstrates the effectiveness of dense lattice dislocations as a means of lowering κ , but also the importance of engineering both thermal and electronic transport simultaneously when designing high-performance thermoelectrics.

High Performance Thermoelectric Materials: Progress and Their Applications

“…Over the years, various strategies have been applied to improve ZT values in a range of TE materials, [2,[85][86][87][88][89][90][91][92][93][94][95][96][97][98][99][100] in which the most effective approaches are to improve the electrical transport properties via optimizing n [1,111] and band engineering, [44,49,[112][113][114] that can decouple σ and S and simultaneously increase their values, for achieving overall high S 2 σ. On the other hand, through nanostructure engineering, [4,16,[115][116][117] κ can be effectively reduced without sacrificing the electrical transport of TE materials, [48,73,118] so that enhanced ZT can be ultimately achieved.…”

Enhanced thermoelectric performance of Na-doped PbTe synthesized under high pressure

“…5d). The plastic deformation process under high pressure facilitates the formation of dense in-grain dislocations, which can scatter mid-frequency phonons and further lower the lattice thermal conductivity [23][24][25]44].…”

“…A diversity of approaches have been applied to PbTe-based materials for ZT enhancements, such as carrier concentration optimization [16,17], introduction of resonance level [18,19], electronic band engineering [6,20,21] and microstructure engineering [8,22]. Recent researches also highlight lattice dislocations as an effective phonon scattering source to further suppress the lattice thermal conductivity of lead chalcogenides [23][24][25][26]. For PbTe, the monovalent sodium has been verified as the most viable p-type dopant [17].…”

Effect of Oxygen Partial Pressure on the Phase Stability of Copper–Iron Delafossites at Elevated Temperatures

“…Whereas commonly used material classes such as chalcogenides [19,20,21,22,23,24,25,26,27,28,29], skudderudites [30,31,32], and polymers [33,34,35,36,37] exhibit good thermoelectric performance at low- and mid-temperature ranges, oxides show their advantages at elevated temperatures above 700 °C. Above all, oxide materials follow the prevailing trend to substitute costly and less abundant thermoelectrics in favor of inexpensive materials.…”