Enhancement of Thermoelectric Figure of Merit by the Insertion of MgTe Nanostructures in p‐type PbTe Doped with Na₂Te

Abstract

The thermoelectric properties of crystalline melt‐grown ingots of p‐type PbTe–xMgTe (x = 1–3 mol%) doped with Na2Te (1–2 mol%) were investigated over the temperature range of 300 K to 810 K. While the powder X‐ray diffraction patterns show that all samples crystallize in the NaCl‐type structure with no MgTe or other phases present, transmission electron microscopy reveals ubiquitous MgTe nanoprecipitates in the PbTe. The very small amounts of MgTe in PbTe have only a small effect on the electrical transport properties of the system, while they have a large effect on thermal transport significantly reducing the lattice thermal conductivity. A ZT of 1.6 at 780 K is achieved for the PbTe containing 2% MgTe doped with 2% Na2Te.

Thermoelectric alloys between PbSe and PbS with effective thermal conductivity reduction and high figure of merit

“…These are behaviors of solid solutions with statistically random atomic distribution. Recently many lead chalcogenides [31][32][33]35,36,39,[48][49][50][51] (including PbSe with PbS addition < 16%) are found with nanostructures on the <10 nm scale using TEM. These features on the nanoscale are not necessarily in conict with our SEM observation at larger scales.…”

Optimizing phonon scattering by nanoprecipitates in lead chalcogenides

“…8,[15][16][17][18][19][20][21] When interpreting experimentally measured thermal conductivity data, researchers most often resort to a Matthiessen approach based on the phonon relaxationtime approximation 16,17,[22][23][24][25][26] assuming a single average (or effective) nanoparticle size. [10][11][12][13][14] However, recent measurements have found that in general the size of nanoprecipitates is distributed across a certain length scale ranging from ∼ 0.5 to ∼ 20 nm. [10][11][12][13][14]27 Given the fact that hierarchically architectured nanostructures scatter phonons more efficiently than monodisperse ones, 14 the underestimation of the effect of nanoparticles in previous studies is worth exploring.…”

“…[10][11][12][13][14] However, recent measurements have found that in general the size of nanoprecipitates is distributed across a certain length scale ranging from ∼ 0.5 to ∼ 20 nm. [10][11][12][13][14]27 Given the fact that hierarchically architectured nanostructures scatter phonons more efficiently than monodisperse ones, 14 the underestimation of the effect of nanoparticles in previous studies is worth exploring. It must be noted that a very recent theoretical work showed that strongly concentrated, bimodal particle size distributions could lower the lattice thermal conductivity of SiGe beyond the single-size limit; 28 however, this kind of distribution bears little resemblance to the ones measured from experiments.…”

“…It must be noted that a very recent theoretical work showed that strongly concentrated, bimodal particle size distributions could lower the lattice thermal conductivity of SiGe beyond the single-size limit; 28 however, this kind of distribution bears little resemblance to the ones measured from experiments. [10][11][12][13][14]27 With the above motivation, it is crucial to quantitatively understand the effect of experimentally observed precipitate size distributions on the thermal transport properties of thermoelectric composites with a view to enhancing thermoelectric performance. Here we look into this issue by calculating the thermal conductivity of two typical thermoelectric materials -PbTe and PbS -with different precipitate types reported in the experimental literature, including Pb, Bi, Bi 2 Te 3 , Sb, Na 2 Te, Ag 2 Te and BaTe, and considering experimentally observable precipitate size distributions.…”

“…In previous models considering only a single effective precipitate size, [10][11][12][13][14]16 the total phonon scattering cross-section σ was simply taken as…”