High Thermoelectric Performance in Supersaturated Solid Solutions and Nanostructured n‐Type PbTe–GeTe

Abstract

Sb-doped and GeTe-alloyed n-type thermoelectric materials that show an excellent figure of merit ZT in the intermediate temperature range (400-800 K) are reported. The synergistic effect of favorable changes to the band structure resulting in high Seebeck coefficient and enhanced phonon scattering by point defects and nanoscale precipitates resulting in reduction of thermal conductivity are demonstrated. The samples can be tuned as single-phase solid solution (SS) or two-phase system with nanoscale precipitates (Nano) based on the annealing processes. The GeTe alloying results in band structure modification by widening the bandgap and increasing the density-ofstates effective mass of PbTe, resulting in significantly enhanced Seebeck coefficients. The nanoscale precipitates can improve the power factor in the low temperature range and further reduce the lattice thermal conductivity (κ lat ). Specifically, the Seebeck coefficient of Pb 0.988 Sb 0.012 Te-13%GeTe-Nano approaches −280 µV K −1 at 673 K with a low κ lat of 0.56 W m −1 K −1 at 573 K. Consequently, a peak ZT value of 1.38 is achieved at 623 K. Moreover, a high average ZT avg value of ≈1.04 is obtained in the temperature range from 300 to 773 K for n-type Pb 0.988 Sb 0.012 Te-13%GeTe-Nano. Microstructure of the Solid Solution SystemMicrostructure information of the Pb 0.988 Sb 0.012 Te-13%GeTe-SS sample is summarized in Figure 2. Figure 2a-c depicts

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

“…[ 28 ] As excess dopants are introduced over the solubility limit, they then precipitate from the matrix as a secondary phase. By controlling the morphology and size of secondary phases, one can expect enhanced scattering of mid‐wavelength phonons, such as in La‐ doped PbTe‐Ag 2 Te, [ 13 ] (PbTe) 0.75 (PbS) 0.15 (PbSe) 0.1 , [ 29 ] and Sb‐ doped PbTe‐GeTe, [ 30 ] . Interestingly, Cu performs diverse roles in modulating the electron/phonon transport in PbTe, that is, Cu dynamically transits between point defects (Cu interstitials) and Cu 2‐ x Te precipitates, simultaneously optimizing the charge carrier concentration and reducing the lattice thermal conductivity.…”

Anisotropy of Selected Mechanical Properties of PbTe

“…The mechanical properties of a given semiconductor can be improved by the crystal doping or alloying with another compound exhibiting well selected properties. Several reports were devoted to the crystal structure, mechanical, and thermoelectric properties of solid solutions grown on the basis of PbTe, like, for example, (Pb,Ge)Te or (Pb,Cd)Te (for details, see e.g., the reports and references therein). The Vickers indentation measurements performed on Pb 0.95 Sn 0.05 Te‐PbS 8% polycrystals demonstrated the mean Vickers hardness ( H V ) equal to 1.18 ± 0.09 GPa for hot pressed powder specimens while the same value of cast specimens was 0.68 ± 0.07 GPa .…”

High‐Performance GeTe‐Based Thermoelectrics: from Materials to Devices

“…Table 4 compares different GeTe‐based thermoelectric materials synthesized by different method, including high‐vacuum and high‐temperature melting [ 80,127,128,140,144–147 ] or solid‐state reaction [ 148,149 ] method. The high temperature can secure sufficient reaction of precursors to form high‐purity and composition‐homogeneous solid solutions.…”