Origin of anisotropic thermal transport in CsPbBr.

We reveal the specific structural and bonding features that result in anisotropic thermal transport for CsPbBr by directional single-crystal measurements and elucidate the bases for the low Debye temperature and speed of sound. This work enhances the research on perovskites and reveals the structural features governing the thermal properties.

Dilute but significant: low cation concentration affects field dependent properties of EuGaSn.

We investigate the temperature and magnetic field-dependent electrical and thermal properties of EuGaSn, revealing a change in electronic structure and an increase in magnetoresistance with increasing field, as well as the origin of magneto-suppressed thermal conductivity of this unconventional inorganic clathrate-I material with very low cation concentration.

Electronic and Thermal Properties of the Cation Substitution-Derived Quaternary Chalcogenide CuInSnSe.

Quaternary chalcogenides continue to be of interest for a variety of technological applications, with physical properties stemming from their structural complexity and stoichiometric variation. In certain structure types, partial vacancies on specific lattice positions present an opportunity to investigate electrical and thermal properties in light of these lattice defects. In this work, we investigated the structural, thermal, and electronic properties of CuInSnSe, a material that belongs to a relatively unexplored class of quaternary chalcogenides with a defect adamantine crystal structure.

Thermal properties of cubic NaSbS: diffusion dominant thermal transport above the Debye temperature.

We elucidate the thermal properties of superionic conductors, which are of intense current interest for solid-state battery applications. The temperature-dependent thermal properties of superionic NaSbS were investigated by analyses of appropriate models revealing that a predominant contribution to thermal transport above the Debye temperature is from thermal diffusion.

Structure, electrical and thermal properties of single-crystal BaCuGdTe.

Single crystals of the quaternary chalcogenide BaCuGdTe were obtained by direct reaction of elements allowing for a complete investigation of the intrinsic electrical and thermal properties of this previously uninvestigated material. The structure was investigated by high-resolution single-crystal synchrotron X-ray diffraction, revealing an orthorhombic crystal structure with the space group Although recently identified as a semiconductor suitable for thermoelectric applications from theoretical analyses, our electrical resistivity and Seebeck coefficient measurements show metallic conduction, the latter revealing strong phonon-drag. Temperature dependent hole mobility reveals dominant acoustic phonon scattering.

Thermal and Electronic Properties of BaMnSe.

The structural, thermal, and electronic properties of BaMnSe were investigated. Analysis of the low-temperature heat capacity revealed a low Debye temperature and a low average speed of sound that, together with the bonding in this material, result in a low thermal conductivity over a relatively large temperature range. Density functional theory and calculated electron localization were employed to investigate the electronic structure and bonding.

Europium Clustering and Glassy Magnetic Behavior in Inorganic Clathrate-VIII EuGaGe.

The temperature- and field-dependent, electrical and thermal properties of inorganic clathrate-VIII EuGaGe were investigated. The type VIII clathrates were obtained from the melt of elements as reported previously. Specifically, the electrical resistivity data show hysteretic magnetoresistance at low temperatures, and the Seebeck coefficient and Hall data indicate magnetic interactions that affect the electronic structure in this material.

Structural and thermal properties of ultralow thermal conductivity BaCuSnSe.

The thermal properties of BaCuSnSe were investigated by measurement of the thermal conductivity and heat capacity. The chemical bonding in this diamagnetic material was investigated using structural data from Rietveld refinement and calculated electron localization. This quaternary chalcogenide is monoclinic (2/), has a large unit cell with 72 atoms in the primitive cell, and a high local coordination environment.

Synthesis, structure, electronic and thermal properties of sphalerite CuZnInS.

Quaternary chalcogenides continue to be of interest due to the variety of physical properties they possess, as well as their potential for different applications of interest. Investigations on materials with the sphalerite crystal structure have only recently begun. In this study we have synthesized sulfur-based sphalerite quaternary chalcogenides, including off-stoichiometric compositions, and investigated the temperature-dependent electronic, thermal and structural properties of these materials.

Synthesis, Bottom up Assembly and Thermoelectric Properties of Sb-Doped PbS Nanocrystal Building Blocks.

The precise engineering of thermoelectric materials using nanocrystals as their building blocks has proven to be an excellent strategy to increase energy conversion efficiency. Here we present a synthetic route to produce Sb-doped PbS colloidal nanoparticles. These nanoparticles are then consolidated into nanocrystalline PbS:Sb using spark plasma sintering.

Structural, Electronic, and Thermal Properties of CdSnAs.

Structural, electrical, and thermal properties of CdSnAs, with analyses from temperature-dependent transport properties over a large temperature range, are reported. Phase-pure microcrystalline powders were synthesized that were subsequently densified to a high-density homogeneous polycrystalline specimen for this study. Temperature-dependent transport indicates -type semiconducting behavior with a very high and nearly temperature independent mobility over the entire measured temperature range, attributed to the very small electron effective mass of this material.

Synthesis, transport properties and electronic structure of p-type CuMnInTe (x = 0, 0.2, 0.3).

The synthesis, electronic structure and temperature dependent transport properties of polycrystalline CuMnInTe (x = 0, 0.2, 0.3) are reported for the first time.

Enhanced thermoelectric performance of heavy-fermion compounds Yb Zn ( = Co, Rh, Ir) at low temperatures.

Thermoelectricity allows direct conversion between heat and electricity, providing alternatives for green energy technologies. Despite these advantages, for most materials the energy conversion efficiency is limited by the tendency for the electrical and thermal conductivity to be proportional to each other and the Seebeck coefficient to be small. Here we report counter examples, where the heavy fermion compounds Yb Zn ( = Co, Rh, Ir) exhibit enhanced thermoelectric performance including a large power factor ( = 74 μW/cm-K; = Ir) and a high figure of merit ( = 0.

Zintl Phases as Reactive Precursors for Synthesis of Novel Silicon and Germanium-Based Materials.

Recent experimental and theoretical work has demonstrated significant potential to tune the properties of silicon and germanium by adjusting the mesostructure, nanostructure, and/or crystalline structure of these group 14 elements. Despite the promise to achieve enhanced functionality with these already technologically important elements, a significant challenge lies in the identification of effective synthetic approaches that can access metastable silicon and germanium-based extended solids with a particular crystal structure or specific nano/meso-structured features. In this context, the class of intermetallic compounds known as Zintl phases has provided a platform for discovery of novel silicon and germanium-based materials.

Structural, Chemical, Electrical, and Thermal Properties of n-Type NbFeSb.

We report on the structural, chemical, electrical, and thermal properties of n-type polycrystalline NbFeSb synthesized by induction melting of the elements. Although several studies on p-type conduction of this half-Heusler composition have recently been reported, including reports of relatively high thermoelectric properties, very little has been reported on the transport properties of  n-type compositions. We combine transport property investigations together with short- and long-range structural data obtained by Mössbauer spectroscopy of iron-57 and antimony-121 and by neutron total scattering, as well as first-principles calculations.

Transport properties of topologically non-trivial bismuth tellurobromides BiTeBr.

Temperature-dependent transport properties of the recently discovered layered bismuth-rich tellurobromides BiTeBr (n = 2, 3) are investigated for the first time. Dense homogeneous polycrystalline specimens prepared for different electrical and thermal measurements were synthesized by a ball milling-based process. While the calculated electronic structure classifies BiTeBr as a semimetal with a small electron pocket, its transport properties demonstrate a semiconductorlike behavior.

Compositional Effects and Electron Lone-pair Distortions in Doped Bournonites.

Bornite materials are naturally occurring systems composed of earth-abundant constituents. Bournonite, a representative of this class of materials, is of interest for thermoelectric applications due to its inherently low thermal conductivity, which has been attributed to the lattice distortions due to stereochemically active electron lone pair distributions. In this computational and experimental study, we present analyses of the lattice structure, electron and phonon dynamics, and charge localization and transfer properties for undoped and Ni and Zn doped bournonites.

Synthesis, Structure, and Electrical Properties of the Single Crystal BaCuAs.

Single crystals of clathrate-I BaCuAs have been synthesized and their structure and electronic properties determined using synchrotron-based X-ray diffraction and first-principles calculations. The structure is confirmed to be Pm3̅ n (No. 223), with lattice parameter a = 10.

Zintl Ions within Framework Channels: The Complex Structure and Low-Temperature Transport Properties of NaGe.

Single crystals of a complex Zintl compound with the composition NaGe were synthesized for the first time using a high-pressure/high-temperature approach. Single-crystal diffraction of synchrotron radiation revealed a hexagonal crystal structure with P6/m space group symmetry that is composed of a three-dimensional sp Ge framework punctuated by small and large channels along the crystallographic c axis. Na atoms are inside hexagonal prism-based Ge cages along the small channels, while the larger channels are occupied by layers of disordered sixfold Na rings, which are in turn filled by disordered [Ge] tetrahedra.

Synthesis, Structure, Te Alloying, and Physical Properties of CuSbS.

Materials with very low thermal conductivities continue to be of interest for a variety of applications. We synthesized CuSbS employing a mechanical alloying technique in order to investigate its physical properties. The trigonal pyramid arrangement of the S atoms around the Sb atoms allows for lone-pair electron formation that results in very low thermal conductivity.

Structure and Transport Properties of Dense Polycrystalline Clathrate-II (K,Ba)(Ga,Sn) Synthesized by a New Approach Employing SPS.

Tin clathrate-II framework-substituted compositions are of current interest as potential thermoelectric materials for medium-temperature applications. A review of the literature reveals different compositions reported with varying physical properties, which depend strongly on the exact composition as well as the processing conditions. We therefore initiated an approach whereby single crystals of two different (K,Ba)(Ga,Sn) compositions were first obtained, followed by grinding of the crystals into fine powder for low temperature spark plasma sintering consolidation into dense polycrystalline solids and subsequent high temperature transport measurements.

Binary Alkali-Metal Silicon Clathrates by Spark Plasma Sintering: Preparation and Characterization.

The binary intermetallic clathrates KSi ( = 0.4; 1.2), RbSi, RbSi and CsSi were prepared from ₄Si₄ ( = K, Rb, Cs) precursors by spark-plasma route (SPS) and structurally characterized by Rietveld refinement of PXRD data.

BC8 Silicon (Si-III) is a Narrow-Gap Semiconductor.

Large-volume, phase-pure synthesis of BC8 silicon (Ia3[over ¯], cI16) has enabled bulk measurements of optical, electronic, and thermal properties. Unlike previous reports that conclude BC8-Si is semimetallic, we demonstrate that this phase is a direct band gap semiconductor with a very small energy gap and moderate carrier concentration and mobility at room temperature, based on far- and midinfrared optical spectroscopy, temperature-dependent electrical conductivity, Seebeck and heat capacity measurements. Samples exhibit a plasma wavelength near 11  μm, indicating potential for infrared plasmonic applications.

Apparatus for the measurement of electrical resistivity, Seebeck coefficient, and thermal conductivity of thermoelectric materials between 300 K and 12 K.

We have developed a custom apparatus for the consecutive measurement of the electrical resistivity, the Seebeck coefficient, and the thermal conductivity of materials between 300 K and 12 K. These three transport properties provide for a basic understanding of the thermal and electrical properties of materials. They are of fundamental importance in identifying and optimizing new materials for thermoelectric applications.