Ga-Doping-Induced Carrier Tuning and Multiphase Engineering in n-type PbTe with Enhanced Thermoelectric Performance

Abstract

P-type lead telluride (PbTe) emerged as a promising thermoelectric material for intermediate-temperature waste-heat-energy harvesting. However, n-type PbTe still confronted with a considerable challenge owing to its relatively low figure of merit ZT and conversion efficiency η, limiting widespread thermoelectric applications. Here, we report that Ga-doping in n-type PbTe can optimize carrier concentration and thus improve the power factor. Moreover, further experimental and theoretical evidence reveals that Ga-doping-induced multiphase structures with nano- to micrometer size can simultaneously modulate phonon transport, leading to dramatic reduction of lattice thermal conductivity. As a consequence, a tremendous enhancement of ZT value at 823 K reaches ∼1.3 for n-type PbGaTe. In particular, in a wide temperature range from 323 to 823 K, the average ZT value of ∼0.9 and the calculated conversion efficiency η of ∼13% are achieved by Ga doping. The present findings demonstrate the great potential in Ga-doped PbTe thermoelectric materials through a synergetic carrier tuning and multiphase engineering strategy.

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

“…A similar behavior for the undoped PbTe is found in the previous study. [41] The lightly doped x = 0.004 also reveals a similar temperature dependence trend of its zT curve.…”

“…It is well known that the substitution of Pb by Ga in PbTe could enhance the zT value. [31,41] The composition of Pb 0.98 Ga 0.02 Te achieves a peak zT = 1.34 at 766 K, [31] while a slightly Garich Pb 0.97 Ga 0.03 Te possess an zT = 1.3 at 823 K. [41] To explore the mechanism yielding the high zT values, we revisit the Ga x Pb 1−x Te alloys (x = 0-0.06) using the Bridgman method. The temperature-dependent zT curve (Figure 1a) of undoped PbTe (x = 0) declines with increasing temperature within 300-573 K. It then increases as the temperature is higher than 600 K. This dramatical change in temperature dependence is due to the co-existence of electron and hole carriers in the undoped PbTe that leads to the significant bipolar behavior at elevated temperature.…”

Synergistically Enhancing Thermoelectric Performance of n‐Type PbTe with Indium Doping and Sulfur Alloying

“…In Figure 2d, the room‐temperature Hall measurement discloses that carrier density significantly goes down with increasing In content, from 4.77 × 10 19 cm −3 in Pb 0.985 Sb 0.015 Te to 7.69 × 10 18 cm −3 in Pb 0.9725 In 0.0125 Sb 0.015 Te. Accordingly, the reduced carrier density benefits high carrier mobility because of lightened carrier‐carrier scattering, [ 22–24 ] and the room‐temperature carrier mobility is sharply boosted from 332 cm 2 V −1 s −1 in Pb 0.985 Sb 0.015 Te to 572 cm 2 V −1 s −1 in Pb 0.975 In 0.01 Sb 0.015 Te. Notably, the temperature‐dependent carrier density in Pb 0.98 In 0.005 Sb 0.015 Te sample undergoes a continuous increase with rising temperature, which is much different from Pb 0.985 Sb 0.015 Te in Figure 2e.…”

“…In Figure 2d, the room-temperature Hall measurement discloses that carrier density significantly goes down with increasing In content, from 4.77 × 10 19 cm −3 in Pb 0.985 Sb 0.015 Te to 7.69 × 10 18 cm −3 in Pb 0.9725 In 0.0125 Sb 0.015 Te. Accordingly, the reduced carrier density benefits high carrier mobility because of lightened carrier-carrier scattering, [22][23][24] and the room-temperature carrier mobility is sharply boosted from 332 cm 2 Figure 2f but also improve the Seebeck coefficient in low temperature range in Figure 2b, finally largely enhancing the power factor ( Figure 2c). The dynamic doping roles of In in PbTe matrix originate from amphoteric In (In 3+ and In 1+ ) atoms that can form impurity levels to trap the free electrons and dynamically optimize the carrier density with increasing temperature.…”

Enhanced thermoelectric properties in N-type Mg2Si0.4−xSn0.6Sbx synthesized by alkaline earth metal reduction

“…[7][8][9][10][11][12] Another strategy is to decrease the relatively independent parameter, lattice thermal conductivity K l , through increased phonon scatterings by multiple crystal defects, such as point defects, grain boundaries, nanoscale precipitations, dislocations, or by taking advantage of the intrinsically anharmonic phonons for low lattice thermal conductivity, etc. [13][14][15][16][17][18] Mg 2 Si-based compounds are treated as promising thermoelectric materials because of their nontoxicity and low cost and because of the abundance of the constituent elements. However, the low power factor and high lattice thermal conductivity in pristine Mg 2 Si materials inhibit the improvement of thermoelectric performance.…”