Search

Clathrates have been reported to form in a variety of different structure types; however, inorganic clathrate-I materials with a low-cation concentration have yet to be investigated. Furthermore, tin-based compositions have been much less investigated as compared to silicon or germanium analogs. We report the temperature-dependent structural and thermal properties of single-crystal Eu2Ga11Sn35 revealing the effect of structure and composition on the thermal properties of this low-cation clathrate-I material. Specifically, low-temperature heat capacity, thermal conductivity, and synchrotron single-crystal x-ray diffraction reveal a departure from Debye-like behavior, a glass-like phonon mean-free path for this crystalline material, and a relatively large Grüneisen parameter due to the dominance of low-frequency Einstein modes. Our analyses indicate thermal properties that are a direct result of the structure and composition of this clathrate-I material. [ABSTRACT FROM AUTHOR]

Temperature-dependent transport properties of the recently discovered layered bismuth-rich tellurobromides BinTeBr (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 Bi2TeBr as a semimetal with a small electron pocket, its transport properties demonstrate a semiconductorlike behavior. Additional bismuth bilayers in the Bi3TeBr crystal structure strengthens the interlayer chemical bonding thus leading to metallic conduction. The thermal conductivity of the semiconducting compositions is low, and the electrical properties are sensitive to doping with a factor of four reduction in resistivity observed at room temperature for only 3% Pb doping. Investigation of the thermoelectric properties suggests that optimization for thermoelectrics may depend on particular elemental substitution. The results presented are intended to expand on the research into tellurohalides in order to further advance the fundamental investigation of these materials, as well as investigate their potential for thermoelectric applications. [ABSTRACT FROM AUTHOR]

The temperature- and field-dependent, electrical and thermal properties of inorganic clathrate-VIII Eu8Ga16Ge30 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. Heat capacity and thermal conductivity data corroborate these findings and reveal the complex behavior due to Eu2+ magnetic ordering and clustering from approximately 13 to 4 K. Moreover, the low-frequency dynamic response indicates Eu8Ga16Ge30 to be a glassy magnetic system. In addition to advancing our fundamental understanding of the physical properties of this material, our results can be used to further the research for potential applications of interest in the fields of magnetocalorics or thermoelectrics. [ABSTRACT FROM AUTHOR]

The thermal properties of Ba3Cu2Sn3Se10 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 (P21/c), has a large unit cell with 72 atoms in the primitive cell, and a high local coordination environment. The Debye temperature (162 K) and average speed of sound (1666 m s−1) are relatively low with a very small electronic contribution to the heat capacity. Ultralow thermal conductivity (0.46 W m−1 K−1 at room temperature) is attributed to the relatively weak chemical bonding and intrinsic anharmonicity, in addition to a large unit cell. This work is part of the continuing effort to explore quaternary chalcogenides with intrinsically low thermal conductivity and identify the features that result in a low thermal conductivity. [ABSTRACT FROM AUTHOR]

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. Insulating to semiconducting transport is observed with stoichiometric variation, and analyses of heat capacity and thermal expansion revealed lattice anharmonicity that contributes to the low thermal conductivity these materials possess. We include similar analyses for CuZn2InSe4 and compare these sphalerite quaternary chalcogenides to that of zinc blende binaries in order to fully understand the origin of the low thermal conductivity these quaternary chalcogenides possess. [ABSTRACT FROM AUTHOR]

The fields of nonlinear optics, photovoltaics, and thermoelectrics have been strongly impacted by materials research, and quaternary chalcogenides are one general class of materials that has recently generated strong interest. An understanding of the thermal properties is paramount in these and other applications of interest. The thermal properties of BaCdSnSe4, a quaternary chalcogenide that is of interest for applications in nonlinear optics, are reported. Specifically, the thermal conductivity over a large temperature range and heat capacity are evaluated in light of the structural features of this material. Low thermal conductivity results from the complex unit cell as well as local dynamic disorder from Cd in the CdSe4 tetrahedra in the crystal structure. The results and analyses reported herein are presented to enhance the fundamental understanding of the thermal properties of these materials, and can be related and applied to other quaternary chalcogenides that are of interest for energy‐related applications. [ABSTRACT FROM AUTHOR]

Quaternary chalcogenides form in different structure types and compositions and are of scientific interest, while their diversity of physical properties exemplifies why they continue to be investigated for potential technological applications. We investigate the thermal properties of BaCu2SnQ4 with trigonal (Q = S) and orthorhombic (Q = Se) crystal structures. BaCu2SnS2Se2 was also synthesized and characterized in order to investigate the effect of alloying on the thermal properties of these quaternary chalcogenides. The low thermal conductivity these materials possess originates from complex phonon spectra and local dynamics of distorted CuQ4 tetrahedra. Our results and analyses are presented in light of the ongoing fundamental interest in these materials as well as their continued interest for energy-related and opto-electronic applications. [ABSTRACT FROM AUTHOR]

Temperature‐dependent thermal properties of phase‐pure polycrystalline ternary chalcogenides Cu4Bi4S9 and Cu4Bi4Se9 are reported. The structure and bonding in these materials result in very low thermal conductivity values (<0.8 W m−1 K−1 at room temperature) for both materials. The lattice contribution, Debye temperatures, and Sommerfeld coefficient are obtained from low‐temperature heat capacity data that also indicate very small electronic contributions to the heat capacity for these materials. This study aids in the identification of new nontoxic, earth‐abundant resistive ternary chalcogenide materials with low thermal conductivity for potential thermal barrier coating and rewriteable storage applications. [ABSTRACT FROM AUTHOR]

Phase‐pure polycrystalline samples of GdTe1.8 and GdTe1.76As0.04 were synthesized by reacting Gd2Te3 with elemental Te and As, employing a small amount of I2 as mineralizer. Polycrystalline specimens were densified by SPS for temperature dependent electrical and thermal properties investigations. The electrical properties indicate that arsenic doping leads to a change from n‐ to p‐type conduction, with an order‐of‐magnitude reduction in resistivity with As doping at room‐temperature as compared to GdTe1.8. The thermal conductivity of both specimens is low, the result of the crystal structure and atypical Te bonding in this material. The results presented are intended to expand on the research into rare‐earth polychalcogenides and advance the fundamental investigation of these materials, as well as begin to evaluate their potential for thermoelectric applications. [ABSTRACT FROM AUTHOR]

The synthesis, electronic structure and temperature dependent transport properties of polycrystalline Cu1+xMn2−xInTe4 (x = 0, 0.2, 0.3) are reported for the first time. These quaternary chalcogenides were synthesized by direct reaction of the elements, followed by solid state annealing and hot press densification. The thermal conductivity is low for all specimens and intrinsic to the material system. Furthermore, the off-stoichiometry specimens illustrate the sensitivity of the transport properties to stoichiometry, with a greater than two-orders-of magnitude increase in carrier concentration with increased Cu content. First principles calculations of the electronic structure are also reported, and are in agreement with the experimental data. This fundamental investigation shows the potential towards further optimization of the electrical properties that, in addition to the intrinsically low thermal conductivity, provides a basis for further research into the viability of this material system for potential energy-related applications. [ABSTRACT FROM AUTHOR]

The low temperature thermal conductivity of YbB44Si2 is investigated. The rare earth boron icosahedra compounds are of interest as potential high temperature thermoelectric materials. The thermal conductivity of YbB44Si2 is relatively large below room temperature, showing crystalline behavior and having a peak exceeding 10 W/m/K at ∼35 K. This departs markedly from the low amorphouslike behavior observed in another rare-earth-containing boron cluster compound: RB66 (R=rare earth). From a comparison and consideration of the various models, we conclude that disorder is the important factor in the generally observed low thermal conductivities of these compounds, with RB66 being exceptionally disordered as compared to YbB44Si2. [ABSTRACT FROM AUTHOR]

Polycrystalline Cu3BiS3 was synthesized and densified using hot pressing in order to investigate the physical properties of this material. Both the thermal conductivity and the Seebeck coefficient of Cu3BiS3 are reported for the first time in order to investigate the thermoelectric properties of this material. The ultralow thermal conductivity coupled with the relatively high Seebeck coefficient, 0.17 W/m-K and 540 μ/K at room temperature, respectively, suggest Cu3BiS3 may show promise for thermoelectric applications. [ABSTRACT FROM AUTHOR]

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)16(Ga,Sn)136 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. Powder X-ray refinement results indicate that the hexakaidecahedra are empty, K and Ba occupying only the decahedra. Their electrical properties depend on composition and have very low thermal conductivities. The structural and transport properties of these materials are compared to that of other Sn clathrate-II compositions. [ABSTRACT FROM AUTHOR]

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. Thermoelectric applications include waste heat recovery for automobile engines and industrial power generators, solid-state refrigeration, and remote power generation for sensors and space probes. The electrical resistivity is measured using a four-probe bipolar technique, the Seebeck coefficient is measured using the quasi-steady-state condition of the differential method in a 2-probe arrangement, and the thermal conductivity is measured using a longitudinal, multiple gradient steady-state technique. We describe the instrumentation and the measurement uncertainty associated with each transport property, each of which is presented with representative measurement comparisons using round robin samples and/or certified reference materials. Transport properties data from this apparatus have supported the identification, development, and phenomenological understanding of novel thermoelectric materials. [ABSTRACT FROM AUTHOR]

Quaternary chalcogenides, particular compounds with the stannite structure-type, are of interest for thermoelectrics applications however tellurium-containing compositions have not been extensively investigated. We report on the synthesis and high temperature thermoelectric properties of p-type stannites Cu2.2Zn0.8SnSe4−xTex (x = 0.1, 0.2, 0.3, and 0.4). The compositions for each specimen were confirmed with a combination of Rietveld refinement and elemental analysis. Hall measurements indicate that holes are the dominant charge carriers in these materials. The electrical resistivity shows little temperature dependence up to 500 K and then increases with increasing temperature. The thermal conductivity decreases with increasing temperature with no indication of increase at higher temperatures suggesting a minimal bipolar diffusion effect in the thermal conductivity although these materials possess relatively small band-gaps as compared to that of other stannite compositions. A maximum ZT value of 0.56 was obtained at 700 K for Cu2.2Zn0.8SnSe3.7Te0.3 due to a relatively high Seebeck coefficient and low thermal conductivity. [ABSTRACT FROM AUTHOR]

We report for the first time the investigation of thermal conductivity for a perovskite-type MOF crystal. In situ single crystal X-ray diffraction technology was employed to track the phase transition of a newly synthesized perovskite MOF. The perovskite MOF crystal exhibits a low thermal conductivity of 1.3 W (K m)−1 in comparison to most of the bulk crystal materials at room temperature. [ABSTRACT FROM AUTHOR]

Polycrystalline NiSe2 was synthesized via a direct solution reaction method, followed by densification by spark plasma sintering. Structural and low-temperature transport properties measurements were employed for characterization. The low temperature thermal conductivity is reported for the first time and is dominated by heat conduction by charge carriers. The polycrystalline NiSe2 has a low electrical resistivity, lower than that reported for single crystal NiSe2, suggesting a very high crystallinity for our polycrystalline specimen. These results are discussed in light of the potential applications for this material. [ABSTRACT FROM AUTHOR]

The article investigates the transport properties of two type-1 clathrate compounds such as Sn24P19.3Br8 and Sn17Zn7P22Br8. These compounds are non-conventional clathrate phases that is formed by cationic framework sequestering anionic guest. Their crystal structure and resistivity, thermal conductivity, Seebeck coefficient and Hall measurement are reported. The article also discusses their potentials for thermoelectric application.

The synthesis, structure, and temperature dependent thermal and electrical properties of off-stoichiometric polycrystalline modified zinc blende quaternary chalcogenides Cu 1.33+x Zn 1.33-x In 1.33 Se 4 , where x ​= ​0, 0.1, 0.2 and 0.3, are investigated. Temperature-dependent electrical properties reveal these compositions to be semiconductors with alteration of the carrier concentration and electrical transport via stoichiometric variation. The thermal conductivity is low for all specimens and intrinsic to these materials. First principles calculations are also reported in establishing a fundamental investigation that illustrates the large variation in stoichiometry that is possible in these materials. This stoichiometric variation results in the observed variation of the transport properties. The results presented reveal fundamental structure-property relationships in these quaternary chalcogenides, and provides a basis for further research into the viability for large stoichiometric variation in other materials that are of interest for technological applications. Synthesis, structure, transport properties, and theoretical calculations on off-stoichiometric variants of modified zinc blende quaternary chalcogenides are reported for the first time. The data for Cu 1.33+x Zn 1.33-x In 1.33 Se 4 indicate an intrinsically low thermal conductivity with a relatively low Debye temperature, while electrical properties are dramatically altered with variation in stoichiometry. [Display omitted] • Off-stoichiometric modified zinc-blende Cu1.33 ​+ ​xZn1.33-xIn1.33Se4 were synthesized, and their structure and temperature-dependent transport properties investigated. • First-principles calculations were reported in order to investigate the phase stability of these materials. • Stoichiometric variation lead to dramatic alteration in electrical transport properties, while the thermal conductivity is intrinsically low for all compositions. • Low temperature specific heat measurements reveal a Debye temperature of 223 ​K. [ABSTRACT FROM AUTHOR]

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. We demonstrate that the introduction of Sb significantly influences the size, geometry, crystal lattice and especially the carrier concentration of PbS. The increase of charge carrier concentration achieved with the introduction of Sb translates into an increase of the electrical and thermal conductivities and a decrease of the Seebeck coefficient. Overall, PbS:Sb nanomaterial were characterized by two-fold higher thermoelectric figures of merit than undoped PbS. [ABSTRACT FROM AUTHOR]

Clathrates have been reported to form in a variety of different structure types; however, inorganic clathrate-I materials with a low-cation concentration have yet to be investigated. Furthermore, tin-based compositions have been much less investigated as compared to silicon or germanium analogs. We report the temperature-dependent structural and thermal properties of single-crystal Eu2Ga11Sn35 revealing the effect of structure and composition on the thermal properties of this low-cation clathrate-I material. Specifically, low-temperature heat capacity, thermal conductivity, and synchrotron single-crystal x-ray diffraction reveal a departure from Debye-like behavior, a glass-like phonon mean-free path for this crystalline material, and a relatively large Grüneisen parameter due to the dominance of low-frequency Einstein modes. Our analyses indicate thermal properties that are a direct result of the structure and composition of this clathrate-I material. [ABSTRACT FROM AUTHOR]

The low temperature thermal conductivity of YbB44Si2 is investigated. The rare earth boron icosahedra compounds are of interest as potential high temperature thermoelectric materials. The thermal conductivity of YbB44Si2 is relatively large below room temperature, showing crystalline behavior and having a peak exceeding 10 W/m/K at ∼35 K. This departs markedly from the low amorphouslike behavior observed in another rare-earth-containing boron cluster compound: RB66 (R=rare earth). From a comparison and consideration of the various models, we conclude that disorder is the important factor in the generally observed low thermal conductivities of these compounds, with RB66 being exceptionally disordered as compared to YbB44Si2. [ABSTRACT FROM AUTHOR]

Quaternary chalcogenides are attractive for a variety of technological fields of interest due to the diverse physical properties these materials possess. Herein, the structural and thermal properties of the disordered chalcopyrite AgInSnSe 4 are reported revealing a distinct relation between its structure and physical properties. Modeling of the experimental temperature-dependent thermal properties revealed an ultralow thermal conductivity (0.47 Wm−1K−1 at room temperature) due to lattice anharmonicity, a low speed of sound and a low Debye temperature. Moreover, first principles electronic structure calculations revealed that the Ag-Se tetrahedra within the crystal structure possess relatively weak bonds due to occupied antibonding states from p - d orbital hybridization, which suppress the thermal conductivity. In order to further quantify our findings, we extended our analyses to include comparisons with other ternary and quaternary adamantine materials, all of which possess a fourfold tetrahedral coordination of atoms, in revealing the origin of the thermal properties in AgInSnSe 4. • The defect chalcopyrite AgInSnSe 4 possesses ultralow thermal conductivity, κ , lower than that of related chalcogenides. • Substitution of Cu by Ag in this chalcopyrite structure induces tetragonal distortions along the c -axis in crystal lattice. • The ultralow κ , low Debye temperature, low speed of sound and large anharmonicity are consequences of lattice distortion. • This is the lowest thermal conductivity thus far reported for a tetrahedrally bonded diamond-like structured material. [ABSTRACT FROM AUTHOR]

• Phase-pure CuInSnS 4 was synthesized allowing for an investigation of the structure-property relationships. • Spinel CuInSnS 4 has an indirect bandgap with strong s -̶ p -̶ d orbital hybridization. • Low frequency optical modes and strong anharmonicity leads to very low thermal conductivity. • The bandgap and low thermal conductivity make it of interest for potential optoelectronic and thermoelectric applications. Quaternary chalcogenides of different structure types continue to be of interest due to the novel physical properties they exhibit and for applications ranging from optoelectronics to energy-related technologies. Herein we report on the electronic and thermal properties of spinel CuInSnS 4. UV–vis–NIR spectroscopy indicates strong absorption in the visible-light region with an indirect bandgap of 1.52 eV. First-principles computations corroborate our experimental data and reveal that the band-edge electronic properties are due to strong p − d and s − p hybridization and antibonding interactions. Analyses of temperature-dependent thermal properties together with first principles simulations reveal strong anharmonicity and low-lying optical branches that hybridize with the acoustic modes effectively suppressing thermal conductivity. This intrinsically very low thermal conductivity is much lower than that of related chalcogenides. Our findings are discussed in the light of ongoing interest in quaternary metal chalcogenide materials and may aid in the development of this and similar chalcogenides for applications of interest. [Display omitted] [ABSTRACT FROM AUTHOR]

The thermal properties of Ba3Cu2Sn3Se10 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 (P21/c), has a large unit cell with 72 atoms in the primitive cell, and a high local coordination environment. The Debye temperature (162 K) and average speed of sound (1666 m s−1) are relatively low with a very small electronic contribution to the heat capacity. Ultralow thermal conductivity (0.46 W m−1 K−1 at room temperature) is attributed to the relatively weak chemical bonding and intrinsic anharmonicity, in addition to a large unit cell. This work is part of the continuing effort to explore quaternary chalcogenides with intrinsically low thermal conductivity and identify the features that result in a low thermal conductivity. [ABSTRACT FROM AUTHOR]

Polycrystalline NiSe2 was synthesized via a direct solution reaction method, followed by densification by spark plasma sintering. Structural and low-temperature transport properties measurements were employed for characterization. The low temperature thermal conductivity is reported for the first time and is dominated by heat conduction by charge carriers. The polycrystalline NiSe2 has a low electrical resistivity, lower than that reported for single crystal NiSe2, suggesting a very high crystallinity for our polycrystalline specimen. These results are discussed in light of the potential applications for this material. [ABSTRACT FROM AUTHOR]

We report on the synthesis and low-temperature transport properties of Ce0.13Co4Ge6Se6 and Yb0.14Co4Ge6Se6. Reitveld refinement was used to identify the structure and stoichiometry of the two compositions. The compounds are skutterudite derivatives with rhombohedral symmetry. The thermal conductivity data were investigated by employing the Debye model with different phonon-scattering parameters. The structural properties have a significant effect on the electrical and thermal properties. This work is part of the continuing effort to explore different skutterudite compositions and structure types, as this class of materials continues to be of interest for thermoelectrics applications. [ABSTRACT FROM AUTHOR]

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. Insulating to semiconducting transport is observed with stoichiometric variation, and analyses of heat capacity and thermal expansion revealed lattice anharmonicity that contributes to the low thermal conductivity these materials possess. We include similar analyses for CuZn2InSe4 and compare these sphalerite quaternary chalcogenides to that of zinc blende binaries in order to fully understand the origin of the low thermal conductivity these quaternary chalcogenides possess. [ABSTRACT FROM AUTHOR]

Sinnerite Cu 6 As 4 S 9 has been identified as a promising material for optoelectronic applications, with potential for other energy-related applications; however, knowledge of the electrical and thermal properties as well as the mechanisms underlying transport in sinnerite is lacking. We present an investigation of the synthesis, structural, thermal and electrical transport properties of stoichiometric and Sn-doped Cu 6 As 4 S 9. Sinnerite has a triclinic lattice structure, with highly distorted local atomic coordination environments that, in part, results in its complex structure and bonding. Our results and analyses indicate As 4 s 2 lone pair-induced distortions and strong lattice anharmonicity that leads to a relatively short phonon mean free path, resulting in intrinsically very low thermal conductivity. The electrical resistivity for both compositions, Cu 6 As 4-x Sn x S 9 (x = 0, 0.2), are relatively high and varies little with temperature, typical of degenerate semiconductors. An increase in mobility and electrical conductivity was obtained by Sn doping in Cu 6 As 3.8 Sn 0.2 S 9. This work demonstrates an effective route to synthesize bulk sinnerite as well as advances the knowledge of the properties of sinnerite, as this and other ternary chalcogenides continue to be of interest for potential technologically significant applications. [Display omitted] • Polycrystalline sinnerites were successfully synthesized by ball milling and solid-state annealing. • The thermal conductivity is intrinsically low (< 1 Wm−1K−1) due to the unique structure and bonding. • The mobility and electrical conductivity increase and the thermal conductivity decreases with Sn doping. • The thermoelectric properties improved by 60% with Sn doping. [ABSTRACT FROM AUTHOR]

New material developments are of paramount importance from the perspective of developing a fundamental understanding of material properties as well as transitioning from materials to devices. Among the different classes of materials of interest, mixed valence Sn compositions have been known to display technologically important properties and are of interest for the design and synthesis of novel compositions for targeted applications. Herein, we report on electronic, optical and thermal properties of the previously unexplored mixed valence composition Ba 4 Sn 4 Se 9 , a material with a direct optical band gap of 2.36 eV. As revealed by single crystal synchrotron X-ray diffraction, Ba 4 Sn 4 Se 9 crystallizes in the orthorhombic space group Pnma with a large unit cell comprised of 58 atoms. Heat capacity data reveals a low Debye temperature with many low frequency optic modes. Our low temperature thermal conductivity data and analyses show that thermal diffusion dominates thermal transport above 80 K. Furthermore, high lattice anharmonicity contributes to the very low thermal conductivity. Our results and analyses will motivate further investigations of this as well as other compositions in the Ba-Sn-Se system, as well as other mixed valence chalcogenides for technological applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The fields of nonlinear optics, photovoltaics, and thermoelectrics have been strongly impacted by materials research, and quaternary chalcogenides are one general class of materials that has recently generated strong interest. An understanding of the thermal properties is paramount in these and other applications of interest. The thermal properties of BaCdSnSe4, a quaternary chalcogenide that is of interest for applications in nonlinear optics, are reported. Specifically, the thermal conductivity over a large temperature range and heat capacity are evaluated in light of the structural features of this material. Low thermal conductivity results from the complex unit cell as well as local dynamic disorder from Cd in the CdSe4 tetrahedra in the crystal structure. The results and analyses reported herein are presented to enhance the fundamental understanding of the thermal properties of these materials, and can be related and applied to other quaternary chalcogenides that are of interest for energy‐related applications. [ABSTRACT FROM AUTHOR]

Understanding the structural properties and chemical bonding in complex multinary chalcogenides is highly valuable, as it provides vital information for controlling their physical properties to suit various technological applications. We report on the structural, thermal, and electronic properties of PbCuBiS 3 by incorporating an experimental and theoretical investigation of this material. Analysis of the experimental temperature-dependent heat capacity and thermal conductivity data show that weak bonding and strong lattice anharmonicity give rise to ultralow thermal conductivity. Chemical bonding information obtained from the density functional theory electronic calculations reveal significant antibonding interactions that underscore the dominant role of the Cu-S tetrahedra on occupied antibonding states, as well as a highly distorted Pb/Bi-S environment inducing weak bonding and strong lattice anharmonicity. This study broadens our understanding of the structure-property relationships for this material, and can be useful for developing this and similar chalcogenide materials for potential applications of interest. [Display omitted] [ABSTRACT FROM AUTHOR]

Polycrystalline quaternary chalcogenides with compositions Cu 1.1 Cd 1.8 In 1.1 Te 4 , Cu 1.3 Cd 1.9 In 0.8 Te 4 , Cu 1.2 Zn 1.8 InTe 4 and Cu 1.2 Zn 1.6 In 1.2 Te 4 were synthesized by reacting the constituent elements and subsequent solid state annealing followed by densification by hot-pressing in order to investigate the transport properties with varying compositions, and therefore carrier densities. The thermal conductivity of these compositions, as well as stoichiometric CuZn 2 InTe 4 and CuCd 2 InTe 4 , are reported for the first time. In addition to the thermal conductivity, resistivity, Seebeck coefficient and compositional stability measurements are also discussed. These materials are p-type semiconductors with very low thermal conductivity values. The potential for improved thermoelectric performance is also discussed. [ABSTRACT FROM AUTHOR]

A hydrothermal approach was employed to efficiently synthesize SnSe nanorods. The nanorods were consolidated into polycrystalline SnSe by spark plasma sintering for low temperature electrical and thermal properties characterization. The low temperature transport properties indicate semiconducting behavior with a typical dielectric temperature dependence of the thermal conductivity. The transport properties are discussed in light of the recent interest in this material for thermoelectric applications. The nanorod growth mechanism is also discussed in detail. [ABSTRACT FROM AUTHOR]

The madocite Pb 17 (Sb 0.75 As 0.25 ) 16 S 41 was synthesized by reaction of binary compounds and densified using hot pressing. The optical band-gap, thermal stability, and temperature-dependent heat capacity and thermal conductivity are reported for the first time. The thermal properties are evaluated using the Debye model. The findings in this work lay the foundation for a more detailed understanding of the physical properties of this material, and is part of the continuing effort in investigating materials with new compositions that possess low thermal conductivity for potential low-cost thermal barrier coating and energy-related applications. [ABSTRACT FROM AUTHOR]

Abstract: Partially Yb-filled Fe substituted polycrystalline p-type skutterudites with nominal compositions Yb x Co2.5Fe1.5Sb12, with varying filler concentrations x, were synthesized by reacting the constituent elements and subsequent solid state annealing, followed by densification by hot-pressing. The compositions and filling fractions were confirmed with a combination of Rietveld refinement and elemental analysis. Their thermoelectric properties were evaluated from 300 to 800K. The Seebeck coefficients for the specimens increase with increasing temperature and plateau at around 750K. The thermal conductivity decreases with increasing Yb filling fraction, and bipolar conduction becomes evident and increases at elevated temperatures. A maximum ZT value of 0.8 was obtained at 750K for Yb0.47Co2.6Fe1.4Sb12. The thermoelectric properties and potential for further optimization are discussed in light of our results. [Copyright &y& Elsevier]

The chemistry of new materials and the effects of chemical substitutions on physical properties continues to be of intense interest as it directly affects many technological fields. The synthesis and temperature dependent transport properties of GdTe 1.62 Se 0.18 were investigated revealing polaronic transport upon simple alloying with selenium. Temperature-dependent resistivity and thermopower measurements indicate strong electron-phonon coupling, as compared to the few other chalcogenides that display such transport. In addition, the low thermal conductivity is intrinsic for this material, and a result of the stacking arrangement in the crystal structure as well as of a statistical disordered Te 2 2– anion. Image, graphical abstract [ABSTRACT FROM AUTHOR]