Thermoelectric stability of Eu- and Na-substituted PbTe

Abstract

As one family of the most investigated thermoelectrics (TE), PbTe-based materials have been developed into state-of-the-art p-type and n-type TE materials. However, there are quite a few studies focusing on the reproducibility of TE properties and microstructure evolution during different heat treatments. In this work, Pb 0.98Àx Na 0.02 Eu x Te (x = 0-0.030) samples were systematically examined after three different kinds of heat treatments: spark plasma sintering (SPS), laser flash measurement (LFA), and long-term annealing. The maximal solubility of Eu (ca. 1.0 atom%) in Pb 0.98Àx Na 0.02 Eu x Te was established at 873 K.The most inhomogeneous samples (samples after SPS) show highest values of figure-of-merit, ZT max , of up to 2.1 at 760 K, due to a large number of micrometer-scale sodium-and europium-rich aggregations in them. After additional heat treatment (LFA measurement or long-term annealing), the ZT max value reduces to 1.6. The distribution of Eu and Na in the samples becomes much more homogeneous, accompanied by increased lattice parameters and decreased carrier concentrations. The long-term annealed samples have the best stable TE properties and good mechanical stability in the cyclic measurements. Surface protection needs to be considered for the temperatures above 773 K in order to avoid material decomposition.

Parallel Dislocation Networks and Cottrell Atmospheres Reduce Thermal Conductivity of PbTe Thermoelectrics

“…[ 23 ] It is worth noting Eu is not enriched at dislocation cores, likely due to the larger ionic radius of Eu and its slower diffusivity in PbTe than Na. [ 24 ] Na atoms are also found to segregate in nanoprecipitates with a high number density of 5 × 10 23 cm –3 and small size (5 nm in diameter) in the alloy, which is further discussed in the supplementary information (Figures S6 and S7, Supporting Information). Only one small Eu‐rich precipitate was occasionally found by APT (Figure S8, Supporting Information), and their number density is hence negligible.…”

Thermoelectric Transport Properties of CdxBiyGe1–x–yTe Alloys

“…Group IV telluride semiconductors, including PbTe, SnTe, GeTe, and their alloys, have long been considered as one of the most important classes of thermoelectric materials. As reported in p-type PbTe, SnTe, and cubic GeTe thermoelectrics, the high performance largely originates from multiple valence bands with a small energy offset and with high valley degeneracies, namely, 4 for L and 12 for Σ bands. , Band convergence reduces the band offset, thus enabling an overall large number of transporting band valleys, which can usually be realized in PbTe − and SnTe − with MnTe-, CdTe-, MgTe-, SrTe-, EuTe-, and YbTe-alloying. Moreover, these alloying activities also lead to an effective decrease in lattice thermal conductivity because of the strong phonon scattering by alloy defects introduced. , …”

Influence of Deformation on Pb1−xInxTe1−yIy and Pb1−x−ySnxInyTe Films

“…[4,5] One of the conventional thermoelectric materials for energy applications is the PbTe semiconductor and solid solutions based on it. [6][7][8][9][10][11][12][13][14][15][16][17][18][19] A promising method to control the thermoelectric properties of PbTe-based materials is doping with non-traditional impurities that form quasi-local (resonant) levels in conduction or valence bands. Traditional impurities do not create shallow hydrogen-like levels in PbTe and related compounds, as these materials have a pronounced ionic component of the chemical bond and the high value of static dielectric constant ε.…”