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Donald T Morelli - One of the best experts on this subject based on the ideXlab platform.
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synthetic versatility reaction pathway and thermal stability of Tetrahedrite nanoparticles
Journal of Materials Chemistry C, 2020Co-Authors: Christine D Fasana, Daniel P. Weller, Daniel L. Stevens, Grace E. Kunkel, Andrew M. Ochs, Mitchel S Jensen, Graciela Garcia E Ponte, Tyler R Macalister, John P Rogers, Donald T MorelliAbstract:Copper-antimony-sulfide compounds have desirable earth-abundant compositions for application in renewable energy technologies, such as solar energy and waste heat recycling. These compounds can be synthesized by bottom-up, solution-phase techniques that are more energy and time efficient than conventional solid-state methods. Solution-phase methods typically produce nanostructured materials, which adds another dimension to control optical, electrical, and thermal material properties. This study focuses on a modified-polyol, solution-phase synthesis for Tetrahedrite (Cu12Sb4S13), a promising thermoelectric material with potential also for photovoltaic applications. To dope the Tetrahedrite and tune material properties, the utility of the modified polyol synthetic approach has been demonstrated as a strategy to produce phase-pure Tetrahedrite that incorporates transition metal (Fe, Co, Ni, Zn, Ag) dopants for Cu, Te dopant for Sb, and Se for S. Six of these reported Tetrahedrite compounds have not previously been made by solution-phase methods. For the bottom-up formation of the Tetrahedrite nanomaterials, the evolution of the chemical phases has been determined by an investigation of the reaction progress as a function of temperature and time. Digenite (Cu1.8S), covellite (CuS), and famatinite (Cu3SbS4) are identified as key intermediates and are consistently observed for both undoped and doped Tetrahedrites. The effect of nanostructuring and doping Tetrahedrite on thermal properties has been investigated. It was found that nanostructured undoped Tetrahedrite has reduced thermal stability relative to samples made by solid-state methods, while the addition of dopants for Cu increased the thermal stability of the material. Crystallinity, composition, and nanostructure of products and intermediates were characterized by powder X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy. Thermal properties were investigated by differential scanning calorimetry and thermal gravimetric analysis. This synthetic study with thermal property analysis demonstrates the potential of the modified polyol method to produce Tetrahedrite and other copper-antimony-sulfide compounds for thermoelectric and photovoltaic applications.
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observation of n type behavior in fe doped Tetrahedrite at low temperature
Materials Today Physics, 2018Co-Authors: Daniel P. Weller, Grace E. Kunkel, Andrew M. Ochs, Donald T Morelli, Mary Elizabeth AndersonAbstract:Abstract Tetrahedrite exhibits favorable thermoelectric properties, while also being composed of non-toxic and earth-abundant elements. Although Tetrahedrite has been studied extensively as a p-type thermoelectric, n-type behavior in this material has not yet been observed. We report the first findings of n-type conductivity in Tetrahedrite observed over a temperature range of 80 to 310 K, with typical p-type conductivity found at higher temperatures. Herein, we characterize electrical and thermal transport properties on these samples from 80 to 673 K. Mechanical alloying and modified polyol synthesis methods were used to synthesize Fe-doped samples (Cu12-xFexSb4S13 with x = 1, 1.3, and 1.5) by solid-state and solution-phase approaches, respectively. Elemental analysis by energy-dispersive X-ray spectroscopy was conducted to investigate the relationship between thermoelectric properties and chemical composition. A maximum ZT = 0.67 at 673 K was obtained for Cu10.5Fe1.5Sb4S13 synthesized by the modified polyol process. Our observation of negative Seebeck coefficient values in the low-temperature regime should serve as a foundation for further study of n-type behavior in Tetrahedrite materials.
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Thermoelectric Performance of Tetrahedrite Synthesized by a Modified Polyol Process
Chemistry of Materials, 2017Co-Authors: Daniel P. Weller, Daniel L. Stevens, Grace E. Kunkel, Andrew M. Ochs, Cameron F. Holder, Donald T Morelli, Mary E AndersonAbstract:Tetrahedrite, a promising thermoelectric material composed of earth-abundant elements, has been fabricated utilizing the rapid and low energy modified polyol process. Synthesis has been demonstrated for undoped and zinc-doped Tetrahedrite samples on the gram scale requiring only 1 h at 220 °C. This method is capable of incorporating dopants and producing particles in the 50–200 nm size regime. For determination of bulk thermoelectric properties, powders produced by this solution-phase method were densified into pellets by spark plasma sintering. Thermopower, electrical resistivity, and thermal conductivity were obtained for temperatures ranging from 323 to 723 K. Maximum ZT values at 723 K were found to be 0.66 and 1.09 for the undoped and zinc-doped Tetrahedrite samples, respectively. These values are comparable to or greater than those obtained using time and energy intensive conventional solid-state methods. Consolidated pellets fabricated using nanomaterial produced by this solution-phase method were ...
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Rapid synthesis of zinc and nickel co-doped Tetrahedrite thermoelectrics by reactive spark plasma sintering and mechanical alloying
Journal of Alloys and Compounds, 2017Co-Authors: Daniel P. Weller, Donald T MorelliAbstract:Tetrahedrite offers advantages over state-of-the-art thermoelectrics, such as lead telluride, because of its low cost and environmentally friendly composition. However, typical sealed-tube synthesis of Tetrahedrite can require multiple days or weeks. In this study, Tetrahedrite co-doped with nickel and zinc was synthesized by two different approaches which both require significantly less time than the conventional furnace-ampoule technique. The first technique utilizes a short ball milling step followed by reactive spark plasma sintering to form Tetrahedrite, and the entire process requires less than 2 h of total synthesis time. The second method involves mechanical alloying to obtain single-phase Tetrahedrite, combined with spark plasma sintering (SPS) for densification. Thermoelectric properties were measured and compared for samples of composition Cu10Ni2-xZnxSb4S13(x = 0, 0.5, 1, 1.5) made by both techniques. Peak ZT values were obtained for Cu10Ni2Sb4S13with ZT = 0.66 at 673 K for SPS reacted and mechanically alloyed samples. Transport properties are comparable between the two techniques, and this provides evidence that supports reactive spark plasma sintering as a viable synthetic technique for Tetrahedrite thermoelectric materials.
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solvothermal synthesis of Tetrahedrite speeding up the process of thermoelectric material generation
ACS Applied Materials & Interfaces, 2015Co-Authors: Derak James, Donald T Morelli, Stephanie L BrockAbstract:Derivatives of synthetic Tetrahedrite, Cu12Sb4S13, are receiving increasing attention in the thermoelectric community due to their exploitation of plentiful, relatively nontoxic elements, combined with a thermoelectric performance that rivals that of PbTe-based compounds. However, traditional synthetic methods require weeks of annealing at high temperatures (450–600 °C) and periodic regrinding of the samples. Here we report a solvothermal method to produce Tetrahedrite that requires only 1 day of heating at a relatively low temperature (155 °C). This allows preparation of multiple samples at once and is potentially scalable. The solvothermal material described herein demonstrates a dimensionless figure of merit (ZT) vs temperature curve comparable to that of solid-state Tetrahedrite, achieving the same ZT of 0.63 at ∼720 K. As with the materials from solid-state synthesis, products from this rapid solvothermal synthesis can be improved by mixing in a 1:1 molar ratio with the Zn-containing natural mineral,...
Daniel P. Weller - One of the best experts on this subject based on the ideXlab platform.
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synthetic versatility reaction pathway and thermal stability of Tetrahedrite nanoparticles
Journal of Materials Chemistry C, 2020Co-Authors: Christine D Fasana, Daniel P. Weller, Daniel L. Stevens, Grace E. Kunkel, Andrew M. Ochs, Mitchel S Jensen, Graciela Garcia E Ponte, Tyler R Macalister, John P Rogers, Donald T MorelliAbstract:Copper-antimony-sulfide compounds have desirable earth-abundant compositions for application in renewable energy technologies, such as solar energy and waste heat recycling. These compounds can be synthesized by bottom-up, solution-phase techniques that are more energy and time efficient than conventional solid-state methods. Solution-phase methods typically produce nanostructured materials, which adds another dimension to control optical, electrical, and thermal material properties. This study focuses on a modified-polyol, solution-phase synthesis for Tetrahedrite (Cu12Sb4S13), a promising thermoelectric material with potential also for photovoltaic applications. To dope the Tetrahedrite and tune material properties, the utility of the modified polyol synthetic approach has been demonstrated as a strategy to produce phase-pure Tetrahedrite that incorporates transition metal (Fe, Co, Ni, Zn, Ag) dopants for Cu, Te dopant for Sb, and Se for S. Six of these reported Tetrahedrite compounds have not previously been made by solution-phase methods. For the bottom-up formation of the Tetrahedrite nanomaterials, the evolution of the chemical phases has been determined by an investigation of the reaction progress as a function of temperature and time. Digenite (Cu1.8S), covellite (CuS), and famatinite (Cu3SbS4) are identified as key intermediates and are consistently observed for both undoped and doped Tetrahedrites. The effect of nanostructuring and doping Tetrahedrite on thermal properties has been investigated. It was found that nanostructured undoped Tetrahedrite has reduced thermal stability relative to samples made by solid-state methods, while the addition of dopants for Cu increased the thermal stability of the material. Crystallinity, composition, and nanostructure of products and intermediates were characterized by powder X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy. Thermal properties were investigated by differential scanning calorimetry and thermal gravimetric analysis. This synthetic study with thermal property analysis demonstrates the potential of the modified polyol method to produce Tetrahedrite and other copper-antimony-sulfide compounds for thermoelectric and photovoltaic applications.
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observation of n type behavior in fe doped Tetrahedrite at low temperature
Materials Today Physics, 2018Co-Authors: Daniel P. Weller, Grace E. Kunkel, Andrew M. Ochs, Donald T Morelli, Mary Elizabeth AndersonAbstract:Abstract Tetrahedrite exhibits favorable thermoelectric properties, while also being composed of non-toxic and earth-abundant elements. Although Tetrahedrite has been studied extensively as a p-type thermoelectric, n-type behavior in this material has not yet been observed. We report the first findings of n-type conductivity in Tetrahedrite observed over a temperature range of 80 to 310 K, with typical p-type conductivity found at higher temperatures. Herein, we characterize electrical and thermal transport properties on these samples from 80 to 673 K. Mechanical alloying and modified polyol synthesis methods were used to synthesize Fe-doped samples (Cu12-xFexSb4S13 with x = 1, 1.3, and 1.5) by solid-state and solution-phase approaches, respectively. Elemental analysis by energy-dispersive X-ray spectroscopy was conducted to investigate the relationship between thermoelectric properties and chemical composition. A maximum ZT = 0.67 at 673 K was obtained for Cu10.5Fe1.5Sb4S13 synthesized by the modified polyol process. Our observation of negative Seebeck coefficient values in the low-temperature regime should serve as a foundation for further study of n-type behavior in Tetrahedrite materials.
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Thermoelectric Performance of Tetrahedrite Synthesized by a Modified Polyol Process
Chemistry of Materials, 2017Co-Authors: Daniel P. Weller, Daniel L. Stevens, Grace E. Kunkel, Andrew M. Ochs, Cameron F. Holder, Donald T Morelli, Mary E AndersonAbstract:Tetrahedrite, a promising thermoelectric material composed of earth-abundant elements, has been fabricated utilizing the rapid and low energy modified polyol process. Synthesis has been demonstrated for undoped and zinc-doped Tetrahedrite samples on the gram scale requiring only 1 h at 220 °C. This method is capable of incorporating dopants and producing particles in the 50–200 nm size regime. For determination of bulk thermoelectric properties, powders produced by this solution-phase method were densified into pellets by spark plasma sintering. Thermopower, electrical resistivity, and thermal conductivity were obtained for temperatures ranging from 323 to 723 K. Maximum ZT values at 723 K were found to be 0.66 and 1.09 for the undoped and zinc-doped Tetrahedrite samples, respectively. These values are comparable to or greater than those obtained using time and energy intensive conventional solid-state methods. Consolidated pellets fabricated using nanomaterial produced by this solution-phase method were ...
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Rapid synthesis of zinc and nickel co-doped Tetrahedrite thermoelectrics by reactive spark plasma sintering and mechanical alloying
Journal of Alloys and Compounds, 2017Co-Authors: Daniel P. Weller, Donald T MorelliAbstract:Tetrahedrite offers advantages over state-of-the-art thermoelectrics, such as lead telluride, because of its low cost and environmentally friendly composition. However, typical sealed-tube synthesis of Tetrahedrite can require multiple days or weeks. In this study, Tetrahedrite co-doped with nickel and zinc was synthesized by two different approaches which both require significantly less time than the conventional furnace-ampoule technique. The first technique utilizes a short ball milling step followed by reactive spark plasma sintering to form Tetrahedrite, and the entire process requires less than 2 h of total synthesis time. The second method involves mechanical alloying to obtain single-phase Tetrahedrite, combined with spark plasma sintering (SPS) for densification. Thermoelectric properties were measured and compared for samples of composition Cu10Ni2-xZnxSb4S13(x = 0, 0.5, 1, 1.5) made by both techniques. Peak ZT values were obtained for Cu10Ni2Sb4S13with ZT = 0.66 at 673 K for SPS reacted and mechanically alloyed samples. Transport properties are comparable between the two techniques, and this provides evidence that supports reactive spark plasma sintering as a viable synthetic technique for Tetrahedrite thermoelectric materials.
Ilho Kim - One of the best experts on this subject based on the ideXlab platform.
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effects of se doping on thermoelectric properties of Tetrahedrite cu 12 sb 4 s 13 z se z
Electronic Materials Letters, 2021Co-Authors: Sunggyu Kwak, Goeun Lee, Ilho KimAbstract:Tetrahedrite Cu12Sb4S13 is composed of abundant non-toxic components and has attracted attention as a promising thermoelectric material with low thermal conductivity at intermediate temperatures. The carrier concentration can be optimized by doping (substituting), thereby maximizing its power factor and reducing its thermal conductivity. In this study, Cu12Sb4S13−zSez (z = 0.1–0.4) compounds were synthesized using mechanical alloying and hot pressing. Our objective was to maintain a high power factor through Se doping and to reduce the lattice thermal conductivity through additional phonon scattering. X-ray diffraction analysis revealed that the lattice constant increased with an increase in Se substitution for the S sites, and all the specimens appeared as a single Tetrahedrite phase. As the Se doping level increased, the carrier (hole) concentration decreased while the mobility increased. The Hall and Seebeck coefficients were both positive, indicating that Se-doped Tetrahedrites exhibit p-type conduction. As the Se substitution increased, the electrical conductivity decreased, but the Seebeck coefficient increased. In addition, Se doping lowered both, the electronic and lattice thermal conductivities, which resulted in decreased thermal conductivity. A maximum dimensionless figure of merit (ZT) of 0.87 was obtained at 723 K for Cu12Sb4S12.8Se0.2 with a high power factor of 0.96 mW m−1 K−2 and a low thermal conductivity of 0.77 W m−1 K−1.
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effects of aging on thermoelectric properties of Tetrahedrite cu _ 12 sb _4 s _ 13
Journal of the Korean Physical Society, 2019Co-Authors: Goeun Lee, Ilho KimAbstract:Tetrahedrite Cu12Sb4S13 was prepared by mechanical alloying and hot pressing. The phase transition, microstructure, and thermoelectric properties (electronic conductivity, Seebeck coefficient, power factor, thermal conductivity, and dimensionless figure of merit) were examined under various aging conditions (atmosphere, temperature, and time). When aged at temperatures above 723 K in air, various oxides (SbO2, Sb2O3, and Sb6O7(SO4)2) and sulfides (Cu9S8, Cu2S, Cu1.96S, and CuSbS2) were formed through oxidation, volatilization, and decomposition of the Tetrahedrite phase. However, the Tetrahedrite phase was stable up to 723 K in vacuum. The pristine specimen exhibited a dimensionless figure of merit of 0.86 at 723 K, resulting from a power factor of 0.95 mW·m−1K−2 and a thermal conductivity of 0.78 W·m−1K−1 at 723 K. For the specimens aged at 523–723 K for 10 h in air, the dimensionless figure of merit varied from 0.81 to 0.92 as the power factor ranged from 0.97 to 1.04 mW·m−1K−2 and the thermal conductivity ranged from 0.80 to 0.85 W·m−1K−1. However, the thermoelectric performance was slightly degraded when the specimen was aged at 723 K for 100 h because of a decreased power factor and increased thermal conductivity.
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preparation of Tetrahedrite cu 12 sb 4 s 13 by mechanical alloying and hot pressing
Journal of Electronic Materials, 2019Co-Authors: Sungyoon Kim, Sunggyu Kwak, Goeun Lee, Ilho KimAbstract:Tetrahedrite Cu12Sb4S13 was synthesized via mechanical alloying (MA) and consolidated using hot pressing (HP) as a solid-state route. Powders with a single phase of Cu12Sb4S13 could be successfully synthesized without post-annealing by controlling the process conditions of MA: 350 rpm for 24 h in an Ar atmosphere. A sintered Tetrahedrite with density close to the theoretical density was obtained via HP at 723 K for 2 h under a pressure of 70 MPa. Thermogravimetric and calorimetric analyses confirmed weight loss and endothermic reactions at temperatures above 853 K, possibly due to the decomposition/melting of the Tetrahedrite and the volatilization/melting of the constituent elements. The synthesized Tetrahedrite is a nondegenerate semiconductor; its electrical conductivity increased with the increase in temperature. Its Seebeck coefficient also increased with the increase in temperature without showing intrinsic conduction up to 773 K. As the HP temperature increased, the power factor decreased because the decrease in the electrical conductivity prevailed over the increase in the Seebeck coefficient. The thermal conductivity had similar low values regardless of the HP temperature. The maximum dimensionless figure-of-merit, ZTmax = 0.87, was obtained at 723 K for the Cu12Sb4S13 hot-pressed at 723 K.
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thermal stability and mechanical properties of thermoelectric Tetrahedrite cu12sb4s13
Journal of Electronic Materials, 2019Co-Authors: Sunggyu Kwak, Goeun Lee, Sungyoon Kim, Ilho KimAbstract:Tetrahedrite Cu12Sb4S13 was prepared by mechanical alloying and hot pressing, and its thermal stability and mechanical properties were examined. The phase transformation (decomposition), chemical composition, elemental redistribution, microstructure, hardness, and three-point bending strength were studied under various aging conditions (atmospheric, temperature, and time). Endothermic peaks were observed at temperatures from 845 K to 892 K and were found to be related to Tetrahedrite decompositions. The Vickers hardness of the pristine specimen was 2.2 GPa on average, and did not significantly change with the aging conditions. The bending strength of the pristine specimen was 26.7 MPa on average, and it remarkably decreased to 6.2 MPa after aging at 723 K for 100 h in air. However, it was 21.4 MPa after aging at 723 K for 100 h in vacuum.
B Lenoir - One of the best experts on this subject based on the ideXlab platform.
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thermoelectric properties of magnesium doped Tetrahedrite cu12 xmgxsb4s13
Journal of Electronic Materials, 2019Co-Authors: B Lenoir, Christophe Candolfi, A Dauscher, Petr Levinsky, J HejtmanekAbstract:Tetrahedrites, naturally occurring sulfosalt minerals, have been shown to exhibit peak ZT values close to unity near 700 K due to the combination of semiconducting-like properties and extremely low lattice thermal conductivity. A wide range of elements can be substituted into Tetrahedrites, each of them affecting the thermoelectric properties. Interestingly, all Tetrahedrites reported to date contain exclusively d- and p-block elements of the periodic table. Here, we demonstrate that magnesium, an s-block element, can be introduced in Cu12Sb4S13. We successfully prepared a series of polycrystalline samples Cu12−xMgxSb4S13 with nominal compositions of x = 0.5, 1.0, 1.5. Powder x-ray diffraction and chemical mapping confirmed that approximately half of the Mg atoms were incorporated into the Tetrahedrite unit cell, while the other half formed electrically insulating MgS precipitates. Thermoelectric properties, measured between 5 K and 673 K, show that the effect of Mg2+ is similar to that of other aliovalent elements substituting for either Cu or Sb. In particular, increasing the Mg content drives the system closer to a semiconducting behavior, leading to a concomitant increase in the thermopower and electrical resistivity and a decrease in the electronic part of the thermal conductivity. Because these two trends counterbalance each other, the overall effect of Mg on the ZT of Cu12Sb4S13 is found to be marginal with a peak ZT of 0.55 at 673 K.
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oxidation studies of cu 12 sb 3 9 bi 0 1 s 10 se 3 Tetrahedrite
Journal of Electronic Materials, 2018Co-Authors: A P Goncalves, E B Lopes, M F Montemor, Judith Monnier, B LenoirAbstract:Tetrahedrites are widespread minerals with general formula Cu10M2Sb4S13 (M = Cu, Mn, Fe, Co, Ni, Zn). Their thermoelectric properties can be tuned through proper doping and reach zT values as high as 1, being considered promising low-cost thermoelectric materials. However, for practical application in thermoelectric devices, it is necessary to establish their ability to operate for long periods under working temperatures and atmospheres. We present herein studies of oxidation in air of Cu12Sb3.9Bi0.1S10Se3 Tetrahedrite at four different temperatures between 230°C and 375°C, together with preliminary corrosion studies in aggressive NaCl electrolyte. Surface oxidation already occurs at the lower studied temperatures, but a strong decrease of the oxidation rate is observed for materials treated at intermediate temperature (275°C), where a continuous surface layer of Cu2−xS forms, pointing to a protective effect of this layer that could be applied in devices operating at such temperatures. For the material treated at higher temperatures (350°C and 375°C), no Tetrahedrite phases were seen after 1500 h, which can be related to the (Tetrahedrite + chalcostibite + antimony → skinnerite) reaction that occurs above 280°C. Corrosion studies indicated that increasing the oxidation temperature unfortunately leads to a decrease of the corrosion resistance of Tetrahedrite-based phases.
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effect of ni bi and se on the Tetrahedrite formation
RSC Advances, 2016Co-Authors: A P Goncalves, E B Lopes, Judith Monnier, Benjamin Villeroy, C Godart, B LenoirAbstract:Materials based on Cu12Sb4S13 Tetrahedrites have been seen in recent years as promising materials for thermoelectric applications. However, the effect of small amounts of additional elements (used to tune the electrical transport properties) on the formation of the phases was not investigated. In this work we present such study, by means of powder X-ray diffraction, scanning electron microscopy complemented with energy-dispersive spectroscopy, and differential scanning calorimetry, using the Taguchi method to design the experiments. The effect of Ni, Bi and Se (i) in the volume percentage of Tetrahedrite, (ii) in the temperature at which the Class III (Tetrahedrite + chalcostibite + antimony → skinnerite) reaction occurs and (iii) in the final melting temperature of Cu12−xNixSb4−yBiyS13−zSez materials rapidly cooled from 950 °C was investigated. Se was observed to have a strong positive influence on the formation of Tetrahedrite, while Ni and Bi were seen to promote the decrease of its volume percentage. A decrease of the Class III reaction and final melting temperatures was also observed after the introduction of Se, with Ni inducing the increase of the reaction and the decrease of the melting temperatures and Bi having only minor effects. The analysis of the microstructures indicate that high Ni concentrations lead to the first solidification of the NiS phase, while in the other compositions the (Tetrahedrite/skinnerite) phase or mixtures of phases is first formed.
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exsolution process as a route toward extremely low thermal conductivity in cu12sb4 xtexs13 Tetrahedrites
Chemistry of Materials, 2015Co-Authors: Y Bouyrie, Christophe Candolfi, A Dauscher, Bernard Malaman, B LenoirAbstract:Achieving extremely low lattice thermal conductivity is an essential requirement for improving the performance of thermoelectric materials. Engineered nanostructures in bulk materials and the search for complex crystal structures that inherently poorly conduct heat are the two main areas of research being currently pursued to achieve this objective. Tetrahedrites, a class of widely studied minerals, show intrinsically very low thermal conductivity values on the order of 0.5 W·m–1·K–1 at 300 K, leading to interesting thermoelectric properties around 700 K. Here, we report on the low-temperature transport properties of a series of synthetic Tetrahedrites Cu12Sb4–xTexS13 and demonstrate that, at low Te concentrations, an exsolution process sets in near 250 K, resulting in the coexistence of two Tetrahedrite phases, likely at the submicrometer length scale. Remarkably, this mechanism triggers a significant reduction of ∼40% in thermal conductivity, which drops to 0.25 W·m–1·K–1 below 200 K. This exceptionally...
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crystal structure electronic band structure and high temperature thermoelectric properties of te substituted Tetrahedrites cu12sb4 xtexs13 0 5 x 2 0
Journal of Materials Chemistry C, 2015Co-Authors: Y Bouyrie, Christophe Candolfi, A Dauscher, Bernard Malaman, V Ohorodniichuk, J Tobola, B LenoirAbstract:Polycrystalline samples of the Tetrahedrite phase Cu12Sb4−xTexS13 with nominal compositions 0.5 ≤ x ≤ 2.0 were synthesized by two different synthesis routes: from precursors and from direct melting of elements. The crystal structure was verified by single-crystal and powder X-ray diffraction (PXRD), both confirming the successful substitution of Te for Sb in both series. Our chemical analyses evidenced differences between the chemical compositions of the two series of samples likely tied to the synthesis method employed and suggesting off-stoichiometry on the Sb site. High-temperature PXRD and differential scanning calorimetry measurements indicate that these materials are stable up to 623 K. Above this temperature, the decomposition process starts and ends up near 748 K where a Cu2−yS-type phase is solely observed. In agreement with the simple electron counting rule and electronic band structure calculations, the electrical resistivity and thermopower increase with increasing x reflecting the gradual shift from a p-type metallic state (x = 0.0) to a p-type semiconducting behavior (x = 2.0). Combined with extremely low lattice thermal conductivity values (κ ≈ 0.5 W m−1 K−1 at 623 K), this substitution enables us to optimize the power factor leading to a maximum thermoelectric figure of merit ZT of about 0.8 at 623 K. These results parallel those obtained in prior studies dealing with partial substitutions on the Cu site and enlarge the possibilities to tune the electrical properties of Tetrahedrites by extrinsic dopants.
Peter Balaz - One of the best experts on this subject based on the ideXlab platform.
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mechano chemical leaching in hydrometallurgy of complex sulphides
Hydrometallurgy, 2006Co-Authors: Peter Balaz, Marcela AchimovicovaAbstract:Abstract This study evaluates the efficiency of chemical leaching of complex antimony and arsenic sulphides (Tetrahedrite, jamesonite, enargite) in alkaline Na 2 S solution following mechanical activation in a laboratory planetary mill and attritor, respectively. Antimony and arsenic are extracted into the leach liquor and the copper or lead-containing solid residues can be exploited in pyrometallurgy. The mechano-chemical leaching of Tetrahedrite concentrate was performed in an industrial attritor in a process called MELT and compared with the conventional chemical leaching of mechanically activated Tetrahedrite. The MELT process leaches antimony several times faster, under similar conditions, than the industry tested hydrometallurgical SUNSHINE process which does not apply milling.
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selective leaching of antimony and arsenic from mechanically activated Tetrahedrite jamesonite and enargite
International Journal of Mineral Processing, 2006Co-Authors: Peter Balaz, Marcela AchimovicovaAbstract:Abstract In this study, the changes in surface area, morphology and leachability of antimony and arsenic from Tetrahedrite, jamesonite and enargite mechanically activated by a high-energy planetary mill were investigated. It appears that the leaching of antimony from Tetrahedrite and jamesonite and arsenic from enargite in alkaline solution of sodium sulphide is temperature-sensitive reaction. The temperature dependencies of all reactions were investigated in the interval 313–363 K. Resulting experimental activation energies were Ea = 111–182 kJ mol− 1 for mechanically activated minerals. The values of Ea are characteristic for processes controlled by surface chemical reactions.
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Leaching of antimony and mercury from mechanically activated Tetrahedrite Cu12Sb4S13
Hydrometallurgy, 1998Co-Authors: Peter Balaz, Jana Ficeriová, Marcela Achimovicova, Robert Kammel, Vladimir ŠepelákAbstract:In this study the physico-chemical transformations and leachability of antimony and mercury from Tetrahedrite concentrate mechanically activated by intensive grinding in a planetary mill were investigated. It has appeared that the leaching of antimony and mercury from Tetrahedrite in alkaline solution of sulphide solution is a structure-sensitive reaction. The temperature dependence of both reactions investigated in the temperature interval 298–363 K has shown that these reactions do not involve any change in mechanism. The experimental activation energies found in this connection were E = 7 kJ mol−1 for the leaching of mercury and E = 33 kJ mol−1 for the leaching of antimony.
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thiourea leaching of silver from mechanically activated Tetrahedrite
Hydrometallurgy, 1996Co-Authors: Peter Balaz, Jana Ficeriová, Vladimir Šepelák, Robert KammelAbstract:Abstract The thiourea leaching of silver from a Tetrahedrite concentrate mechanically activated in a planetary mill or an attritor was studied. It was found that the two types of equipment gave rise to different rates of new surface formation and of crystal structure disordering. The rate of thiourea leaching of silver from Tetrahedrite (Cu,Ag)10(Zn,Fe)2(Sb,As)4S13 is a structure-sensitive quantity, while the dependence of the rate constant of leaching on the empirical coefficient S A (1 − R) (SA = specific surface, R = disordering of Tetrahedrite structure) exhibits a linear character with equal slope for both types of mills. The results are also of prognostic character because they enable us to propose suitable equipment for intensive grinding depending on the demand for fineness or reactivity of the solid substances.
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Application of attrition grinding in alkaline leaching of Tetrahedrite
Minerals Engineering, 1995Co-Authors: Peter Balaz, F. Sekula, Š Jakabský, Robert KammelAbstract:This paper is concerned with the leaching of calcined Tetrahedrite in a combined mechanochemical and chemical regime. The application of alkaline Na2S solution enables us, at temperatures of 84-96°C and atmospheric pressure, to achieve total extraction of Sb and As with leaching times of 15-20 min for Sb and 20-40 min for As. The applied liquid/solid ratio (4.8-2.5) and energy inputs (82-157 kWh/t) are acceptable from the view-point of plant operation. The process of mechanochemical leaching, including simultaneous intensive grinding and leaching, enhances the extraction of metals from refractory Tetrahedrite. © 1995.
