High Figure of Merit in Gallium-Doped Nanostructured n-Type PbTe-xGeTe with Midgap States

Abstract

PbTe-based thermoelectric materials are some of the most promising for converting heat into electricity, but their ntype versions still lag in performance the p-type ones. Here, we introduce midgap states and nanoscale precipitates using Gadoping and GeTe-alloying to considerably improve the performance of n-type PbTe. The GeTe alloying significantly enlarges the energy band gap of PbTe and subsequent Ga doping introduces special midgap states that lead to an increased density of states (DOS) effective mass and enhanced Seebeck coefficients. Moreover, the nucleated Ga 2 Te 3 nanoscale precipitates and off-center discordant Ge atoms in the PbTe matrix cause intense phonon scattering, strongly reducing the thermal conductivity (∼0.65 W m −1 K −1 at 623 K). As a result, a high room-temperature thermoelectric figure of merit ZT ∼ 0.59 and a peak ZT max of ∼1.47 at 673 K were obtained for the Pb 0.98 Ga 0.02 Te-5%GeTe. The ZT avg value that is most relevant for devices is ∼1.27 from 400 to 773 K, the highest recorded value for n-type PbTe.

From Dislocation to Nano‐Precipitation: Evolution to Low Thermal Conductivity and High Thermoelectric Performance in n‐Type PbTe

“…b) The averaged zT values calculated with 300-673 K, for various n-type PbTe with different dopants: the Sb-doped PbTe, [50] the Ag-doped PbTe, [44] the Ga-doped PbTe, [31,41] the (I, Sb)-doped PbTe, [26] the Cu-doped PbTe, [6] and the (Ga, Ge)-doped PbTe. [55] Information). [6,8,10,11,[24][25][26]31,[41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] The breakthrough shall be attributed to their microstructures and phases, in which a phase diagram could interpret the relationship.…”

“…[55] Information). [6,8,10,11,[24][25][26]31,[41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] The breakthrough shall be attributed to their microstructures and phases, in which a phase diagram could interpret the relationship. Figure 2a shows the isothermal section of ternary Pb-Te-Ga at 673 K, which is constructed by an experimental approach.…”

“…One can conclude that the optimal PF curve describes a similar x Te (x = 0-0.02), the Ga y (PbTe) 1−y (y = 0.004-0.012), and the Ga z PbTe 1−z (z = 0.006, 0.01). d) The average power factor calculated within 300-673 K, for various n-type PbTe with different dopants: the Ag-doped PbTe, [44] the Sb-doped PbTe, [50] the Ga-doped PbTe, [31,41] the (Ga, Ge)-doped PbTe, [55] the (I, Sb)-doped PbTe, [26] and the Cu-doped PbTe. [6] Table 1.…”

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

“…Specifically, n ‐ type electron conduction is dominated by a relatively simple light conduction band while p ‐ type hole conduction is determined by the degeneracy between a light valence band at Γ and a heavy valence band at Σ, which can be rationally designed as widely reported. [ 3,18,20–23 ]…”

Influence of Nanostructuration on PbTe Alloys Synthesized by Arc-Melting

“…In recent years, tellurium-based compounds are among the most efficient thermoelectric materials, for instance, Bi 2 Te 3 , is widely used in near room temperature applications [1,14], or GeTe and its alloys [15,16,17,18,19], rare-earth tellurides [20,21,22,23,24], or PbTe [25,26,27,28,29]. PbTe-based thermoelectrics are the best performing materials in the middle-temperature range of 500 to 900 K [1,3,4,30,31], so they are one of the best options available for harvesting wasted thermal energy. In particular, Ag and Sb doping in the so-called LAST-type compounds, induce an excellent performance [30,32,33].…”