Thermoelectric Properties as a Function of Electronic Band Structure and Microstructure of Textured Materials

Abstract

A tool has been developed at Fraunhofer-IPM to calculate the transport properties of thermoelectric material by using its band structure described in terms of effective masses and the location of the ellipsoids in reciprocal space. The calculated transport properties are compared with experimental data measured on bismuth telluride, antimony telluride, and bismuth antimony telluride. Polycrystalline specimens have been prepared by spark plasma sintering (Fraunhofer-IFAM). Electron backscattering diffraction analysis of sample cross-sections yields the frequency distribution of grain orientations. This texture information permits the generation of appropriate finite-element models of the polycrystalline microstructure (TU Dresden). By means of the commercial code COMSOL, which allows anisotropic thermoelectric properties to be taken into account, the effective electrical and thermal conductivities as well as the Seebeck coefficient both parallel and perpendicular to the pressing direction have been calculated.

Harnessing Topological Band Effects in Bismuth Telluride Selenide for Large Enhancements in Thermoelectric Properties through Isovalent Doping

“…Boltzmann Modeling of Properties, and First Principles Calculations : We modeled σ and α using, where g ( E ) is the density‐of‐states, τ ( E ) the charge scattering relaxation time from Matthiessen's rule, ( E ) the carrier band velocity, and f ( E F , E ) the Fermi‐Dirac distribution. Literature values of σ , α , n , and p for Bi 2 Te 2 Se and Bi 2 Te 3 single‐crystals were used to obtain model parameters, e.g., phonon and defect scattering potentials, charge carrier effective masses, and bandgap E g . We chose self‐consistent inertial and DOS effective masses to capture crystalline anisotropy in σ , and isotropy in α .…”

Anisotropic Analysis of Nanocrystalline Bismuth Telluride Thin Films Treated by Homogeneous Electron Beam Irradiation

“…To estimate the in-plane and cross-plane transport properties of the Bi 2 Te 3 thin lms, we used a simple model based on the transport properties of the basal plane (perpendicular to the c-axis) and lateral plane (parallel to the c-axis) of singleand poly-crystal Bi 2 Te 3 , 5,[28][29][30][31] as presented in Table 1. At an F value of zero, the transport property values of the basal and lateral planes are expected to converge, so the normalized value of the averaged property values is equal to 1.0, as shown in Fig.…”

“…Finally, we also assumed that the degree of anisotropy was not dependent on the crystallite size. 1.85 29) 1.50 30) −206.7…”

“…−240 29) 1. 2 28) 1.27 29) 0.0 0.0 1.37 29) 1.35 30) 1.03 5) 1.00 29) 1.25 28) 1.16 29) 1.17 5) 0.25 29) 0.31 30) 0.94 5) 1.00 29) 0.58 28) 0.68 29) 0 Figure 5 shows the in-plane and cross-plane electrical transport property values (electrical conductivity, Seebeck coef cient, power factor) of the Bi 2 Te 3 thin lms as a function of the EB irradiation dose.…”

Lattice dynamics in Bi2Te3and Sb2TeBessas1, Sergueev2, Wille3 et al. 2012Phys. Rev. BSelf Cite

“…If the direction dependent acoustic cutoff energies were available from our measurements, the thermal conductivity ratio κ k in ⊥c L /κ k in ||c L could be estimated using Eq. (1) and compared to reference data, 71 κ L⊥c = 1.73 Wm −1 K −1 and κ L||c = 0.64 Wm −1 K −1 . The same holds for the composite speed of sound.…”