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

Abstract

Lead telluride (PbTe) has long been regarded as an excellent thermoelectric material at intermediate temperature range (573–873 K); however, n‐type PbTe's performance is always relatively inferior to its p‐type counterpart mainly due to their different electronic band structures. In this work, an ultrahigh thermoelectric quality factor (µ/κL ≈ 1.36 × 105 cm3 KJ−1 V−1) is reported in extra 0.3% Cu doped n‐type (PbTe)0.9(PbS)0.1 as‐cast ingots. Transmission electron microscopy (TEM) characterization reveals that excess PbS exists in PbTe matrix as strained endotaxial nanoprecipitates, which affect electrical and thermal conduction discriminately: (1) coherent PbTe/PbS lattice minimizes the interface scattering of charge carriers; (2) periodic strain centers at PbTe/PbS interface exhibit intensive strain contrast, which can strongly scatter heat‐carrying phonons. Electron backscattered diffraction (EBSD) characterization illustrates very large PbTe grains (≈1 mm) in these as‐cast ingots, ensuring an extremely low grain boundary scattering rate thus a very high charge carrier mobility. Eventually, a remarkably high ZTmax ≈ 1.5 at 773 K and an outstanding ZTavg ≈ 1.0 between 323 and 773 K are simultaneously achieved in the (PbTe)0.9(PbS)0.1 +0.3%Cu sample; these values are highly competitive with reported state‐of‐art n‐type PbTe materials.

High‐Ranged ZT Value Promotes Thermoelectric Cooling and Power Generation in n‐Type PbTe

“…Therefore, the lattice thermal conductivity is dramatically reduced from ≈2.2 Wm −1 K −1 in Pb 0.985 Sb 0.015 Te to ≈0.53 Wm −1 K −1 in PbTe‐30%SnSe‐1.5%Cu at room temperature, and continuously decreases to ≈0.4 Wm −1 K −1 at 773 K. More details about thermal transport properties can be found in Figure S8 (Supporting Information). Compared with other high‐performance n‐type PbTe‐based materials, such as PbTe‐CuSbSe 2 , [ 18a ] PbTe‐Cd, [ 29 ] PbTe‐Cu 2 Te, [ 18b ] PbTe‐Cu, [ 20 ] PbTe‐InSb, [ 30 ] PbTe‐S‐Cu, [ 31 ] and PbTe‐Se‐Cu, [ 32 ] PbTe‐30%SnSe‐1.5%Cu presents a relatively low lattice thermal conductivity especially at 300–573 K, shown in Figure 6c. Combining the largely reduced thermal conductivity and boosted power factor, the room‐temperature ZT value obtains sevenfold increase, from ≈0.1 in Pb 0.985 Sb 0.015 Te to ≈0.7 in PbTe‐30%SnSe‐1.5%Cu, shown in Figure 6d.…”

Silver Atom Off-Centering in Diamondoid Solid Solutions Causes Crystallographic Distortion and Suppresses Lattice Thermal Conductivity

“…As a result, tremendous progress has been achieved in boosting thermoelectric performance. Therefore, low heat conductivity has been considered an essential requirement for high thermoelectric performance, and most advanced thermoelectric materials possess an extremely low lattice thermal conductivity, such as the PbTe, − SnSe, − GeTe, − Cu 2 Se, ,, zintl phases, − and Mg 3 (Bi,Sb) 2 , − to name a few.…”

Engineering an atomic-level crystal lattice and electronic band structure for an extraordinarily high average thermoelectric figure of merit in n-type PbSe

“…11 Consequently, n H can be increased in an unconventional pathway. (2) It may behave like a liquid and suppress k lat at elevated temperatures, [34][35][36][37] where this TE system operates most efficiently.…”