When band convergence is not beneficial for thermoelectrics.

Band convergence is considered a clear benefit to thermoelectric performance because it increases the charge carrier concentration for a given Fermi level, which typically enhances charge conductivity while preserving the Seebeck coefficient. However, this advantage hinges on the assumption that interband scattering of carriers is weak or insignificant. With first-principles treatment of electron-phonon scattering in the CaMgSb-CaZnSb Zintl system and full Heusler SrSbAu, we demonstrate that the benefit of band convergence can be intrinsically negated by interband scattering depending on the manner in which bands converge.

Metallic n-Type Mg Sb Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance.

Mg (Sb,Bi) alloys have recently been discovered as a competitive alternative to the state-of-the-art n-type Bi (Te,Se) thermoelectric alloys. Previous theoretical studies predict that single crystals Mg (Sb,Bi) can exhibit higher thermoelectric performance near room temperature by eliminating grain boundary resistance. However, the intrinsic Mg defect chemistry makes it challenging to grow n-type Mg (Sb,Bi) single crystals.

Synthesis and characterization of vacancy-doped neodymium telluride for thermoelectric applications.

Thermoelectric materials exhibit a voltage under an applied thermal gradient and are the heart of radioisotope thermoelectric generators (RTGs), which are the main power system for space missions such as I, II, and the Mars rover. However, materials currently in use enable only modest thermal-to-electrical conversion efficiencies near 6.5% at the system level, warranting the development of material systems with improved thermoelectric performance.

Effect of anion substitution on the structural and transport properties of argyrodites CuPSeS.

Inspired by the good performance of argyrodites as ion conducting thermoelectrics and as solid electrolytes we investigated the effect of isovalent S substitution for Se in CuPSe. At room temperature CuPSe crystallizes in the primitive cubic β-polymorph of the argyrodite structure and transforms to the face-centered high-temperature (HT) γ-modification above 320 K. The transition for the homologous CuPS occurs at 510 K.

Micro- and Macromechanical Properties of Thermoelectric Lead Chalcogenides.

Both n- and p-type lead telluride (PbTe)-based thermoelectric (TE) materials display high TE efficiency, but the low fracture strength may limit their commercial applications. To find ways to improve these macroscopic mechanical properties, we report here the ideal strength and deformation mechanism of PbTe using density functional theory calculations. This provides structure-property relationships at the atomic scale that can be applied to estimate macroscopic mechanical properties such as fracture toughness.

Superstrengthening Bi_{2}Te_{3} through Nanotwinning.

Bismuth telluride (Bi_{2}Te_{3}) based thermoelectric (TE) materials have been commercialized successfully as solid-state power generators, but their low mechanical strength suggests that these materials may not be reliable for long-term use in TE devices. Here we use density functional theory to show that the ideal shear strength of Bi_{2}Te_{3} can be significantly enhanced up to 215% by imposing nanoscale twins. We reveal that the origin of the low strength in single crystalline Bi_{2}Te_{3} is the weak van der Waals interaction between the Te1 coupling two Te1─Bi─Te2─Bi─Te1 five-layer quint substructures.

A computational assessment of the electronic, thermoelectric, and defect properties of bournonite (CuPbSbS) and related substitutions.

Bournonite (CuPbSbS) is an earth-abundant mineral with potential thermoelectric applications. This material has a complex crystal structure (space group Pmn2 #31) and has previously been measured to exhibit a very low thermal conductivity (κ < 1 W m K at T ≥ 300 K). In this study, we employ high-throughput density functional theory calculations to investigate how the properties of the bournonite crystal structure change with elemental substitutions.

Structure and Failure Mechanism of the Thermoelectric CoSb/TiCoSb Interface.

The brittle behavior and low strength of CoSb/TiCoSb interface are serious issues concerning the engineering applications of CoSb based or CoSb/TiCoSb segmented thermoelectric devices. To illustrate the failure mechanism of the CoSb/TiCoSb interface, we apply density functional theory to investigate the interfacial behavior and examine the response during tensile deformations. We find that both CoSb(100)/TiCoSb(111) and CoSb(100)/TiCoSb(110) are energetically favorable interfacial structures.