Coherent Sb/CuTe Core/Shell Nanostructure with Large Strain Contrast Boosting the Thermoelectric Performance of n‐Type PbTe

Abstract

The exploration of n‐type PbTe as thermoelectric materials always falls behind its p‐type counterpart, mainly due to their quite different electronic band structure. In this work, elemental Sb and Cu2Te are introduced into an n‐type base material (PbTe)81‐Sb2Te3. The introduction of extra Sb can effectively tune the concentration of electrons; meanwhile, Sb precipitates can also scatter low‐energy electrons (negatively contribute to the Seebeck coefficient) thus enhance the overall Seebeck coefficient. The added Cu2Te is found to always co‐precipitate with Sb, forming an interesting Sb/CuTe core/shell structure; moreover, the interface between core/shell precipitates and PbTe matrix simultaneously shows coherent lattice and strong strain contrast, beneficial for electron transport but adverse to phonon transport. Eventually, a peak figure of merit ZTmax ≈ 1.6 @ 823K and simultaneously an average ZT ≈ 1.0 (323–823 K) are realized in the (PbTe)81Sb2Te3‐0.6Sb‐2Cu2Te sample, representing the state of the art for n‐type PbTe‐based thermoelectric materials. Moreover, for the first time the three existing forms of Cu atoms in Cu2Te alloyed PbTe are unambiguously clarified with aberration‐corrected scanning transmission electron microscopy (Cs‐STEM).

Strained Endotaxial PbS Nanoprecipitates Boosting Ultrahigh Thermoelectric Quality Factor in n‐Type PbTe As‐Cast Ingots

“…Eventually, in the as‐cast ingot of composition (PbTe) 0.9 (PbS) 0.1 +0.3% Cu, a figure of merit of ZT max ≈ 1.5 at 773 K was achieved, and the corresponding ZT avg (323–773 K) reached ≈1.0, both of which are among the highest ones for all reported n‐type PbTe‐based thermoelectrics. [ 12,28–30,32,34 ] Remarkably, we simultaneously realized a high carrier mobility μ ≈ 1050 cm 2 (Vs) −1 and a low lattice thermal conductivity κ L ≈ 0.77 W (mK) −1 at the carrier concentration ≈1.41 × 10 19 cm −3 , engendering an ultrahigh thermoelectric quality factor ( µ /κ L ≈ 1.3 × 10 5 cm 3 KJ −1 V −1 ) thanks to the decoupled scattering of strained endotaxial PbS precipitates on charge carriers and heat‐carrying phonons.…”

“…[ 26 ] In contrast, due to the large band offset between the light and heavy conduction bands (>0.3 eV) [ 12 ] that results in a low band degeneracy, the thermoelectric performance of n‐type PbTe still cannot compete with its p‐type counterpart, until some impressive results were reported recently. [ 12,27–31 ] Iodine doping in PbTe 0.9988 I 0.0012 [ 9 ] and La doping in (PbTe) 0.945 (Ag 2 Te) 0.055 [ 32 ] were found effective to tuning the electron concentration for an optimal peak ZT ; recently, dynamic doping in PbTe‐0.2% Cu [ 29 ] and energy filtering in PbTe‐4% InSb [ 12 ] were proved able to gain even better thermoelectric performance. To reduce the lattice thermal conductivity, spinodal decomposition and nucleation in (Pb 0.95 Sn 0.05 Te) 0.92 (PbS) 0.8 , [ 33 ] nanostructured in PbTe 0.7 S 0.3 , [ 18 ] PbTe‐X (X = 2% Sb, Bi, or Pb), [ 17 ] hierarchical structure in Cu 3.3 Pb 100 Sb 3 Te 100 Se 6 [ 23 ] were also well explored.…”

Eliciting High‐Performance Thermoelectric Materials via Phase Diagram Engineering: A Review

“…In the recent decade, innovative strategies, including dynamic doping, [143,144] phase diagram engineering, [27] lattice strain engineering, [145][146][147] and so on, are utilized to improve the zT values of n-type PbTe, which yields outstanding results. [147][148][149][150] For example, aliovalent defects in a doped lead telluride could manipulate the charge transport and atomic vibrational properties, resulting in the optimized TE properties. [151,152] Among these potential strategies, the phase diagram engineering emerges as a new approach to disclose the relationship between the TE performance, microstructure, and phase stability.…”

“…The best-performing (Cu, Se)-PbTe achieves an extraordinary peak zT % 1.6 at 750 K. [153] The evolution of the microstructure, strain field, and defects significantly influences the κ L . [147,[157][158][159][160][161][162] The strain field can effectively reduce κ L due to the severe lattice distortion. [149,155,165] The formation of point defects, [163] dislocations, [160] grain boundary, [162] and precipitates [164] induces the strain field, which affects the phonon traveling to different levels.…”

“…The progress in the n‐type PbTe was much slower than the p‐type counterpart in the last decade, and that drives the research interests toward high‐performance n‐type lead tellurides. In the recent decade, innovative strategies, including dynamic doping, [ 143,144 ] phase diagram engineering, [ 27 ] lattice strain engineering, [ 145–147 ] and so on, are utilized to improve the zT values of n‐type PbTe, which yields outstanding results. [ 147–150 ] For example, aliovalent defects in a doped lead telluride could manipulate the charge transport and atomic vibrational properties, resulting in the optimized TE properties.…”