The Experts below are selected from a list of 32985 Experts worldwide ranked by ideXlab platform
Yongjun Tian - One of the best experts on this subject based on the ideXlab platform.
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High Pressure Synthesis and thermoelectric properties of Ba-filled CoSb3 skutterudites
Journal of Materials Science: Materials in Electronics, 2017Co-Authors: Yulong Kang, Long Zhang, Chen Chen, Qian Zhang, Hao Sun, Yongjun TianAbstract:The filling behavior of barium into voids of CoSb3 under High Pressure was investigated with the first principles calculations, revealing that the filling fraction limit can be further increased under High Pressure. Inspired by the theoretical investigation result, we synthesized Ba-filled CoSb3 with a High Pressure Synthesis method. The products show the skutterudite structure of \(\operatorname{Im}\bar{3}\) symmetry. The maximal filling fraction of Ba in CoSb3 is increased to 0.51. The power factor is significantly enhanced meanwhile the lattice thermal conductivity is dramatically suppressed after Ba filling, and ZT of Ba0.51Co4Sb12 reaches a value of ca. 1.0 at 883 K. Compared with the traditional solid state reaction method for fabricating elemental-filled skutterudites, the High Pressure Synthesis method shows the advantages of fast process, broadening fillable elements, and increasing the filling fraction.
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High Pressure Synthesis and thermoelectric properties of polycrystalline Bi2Se3
Journal of Alloys and Compounds, 2017Co-Authors: Yulong Kang, Long Zhang, Chen Chen, Qian Zhang, Changzeng Fan, Yongjun TianAbstract:Abstract Polycrystalline Bi 2 Se 3 samples were produced with High Pressure Synthesis. X-ray diffraction measurements indicated that the crystal structure of Bi 2 Se 3 is closely related to the synthetic Pressure. While the trigonal phase with R 3 ¯ m symmetry was achieved at 1 GPa, the orthorhombic phase with Pnma symmetry was dominant at Pressure Higher than 3 GPa. This result is consistent with the first-principles calculations. XRD and SEM measurements revealed an anisotropic texture in the R 3 ¯ m Bi 2 Se 3 sample densified with spark plasma sintering, which was further demonstrated in the thermoelectric properties. The Highest ZT of 0.37 was achieved at 560 K along the compressing direction of spark plasma sintering, a relatively High value for undoped Bi 2 Se 3 .
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Sodium doped polycrystalline SnSe: High Pressure Synthesis and thermoelectric properties
Journal of Alloys and Compounds, 2017Co-Authors: Bowen Cai, Long Zhang, Hao Sun, Peng Zhao, Yongjun TianAbstract:Abstract p -type Na x Sn 1- x Se bulks were prepared by combining High Pressure Synthesis and spark plasma sintering. The final samples were characterized with XRD and SEM, and demonstrated strong structural anisotropy with the b-c planes in the grains preferentially orientated perpendicular to the SPS compressing direction. High Pressure prompted Na doping process and increased the hole concentration up to 3.08 × 10 19 cm −3 in Na 0.02 Sn 0.98 Se, leading to significant increased electrical conductivity and power factor. Meanwhile, the thermal conductivity was substantially suppressed after Na doping. The Highest ZT of 0.87 was achieved in the optimal Na 0.02 Sn 0.98 Se at 798 K measured along the direction perpendicular to the SPS compressing.
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High Pressure Synthesis of p-Type CeyFe4−xCoxSb12 Skutterudites
Materials (Basel Switzerland), 2016Co-Authors: Yadi Liu, Long Zhang, Qian Zhang, Yongjun TianAbstract:Co-substituted p-Type CeFe4−xCoxSb12 skutterudites were successfully synthesized with a High Pressure Synthesis method. The structure, composition, and thermoelectric properties were investigated. The obtained CeyFe4−xCoxSb12 samples show the skutterudite structure of I m 3 ¯ symmetry. The hole concentration decreases with elevating Co substitution level, leading to increased Seebeck coefficient and electrical resistivity. Meanwhile, the filling fraction of Ce decreases, which is unfavorable for reducing the lattice thermal conductivity. As a result, the thermoelectric performance of CeyFe4−xCoxSb12 deteriorates with Higher Co content. The maximal ZT of 0.91 was achieved at 763 K for the optimal Ce0.92Fe4Sb12 sample.
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High Pressure Synthesis of p-type Fe-substituted CoSb3 skutterudites
Journal of Materials Science: Materials in Electronics, 2016Co-Authors: Yadi Liu, Long Zhang, Chen Chen, Qian Zhang, Yongjun TianAbstract:Fe-substituted CoSb3 skutterudites were successfully synthesized with High Pressure Synthesis method. The composition, structure, and thermoelectric properties were investigated. Co4−xFexSb12 samples have the skutterudite structure of \(\text{Im} \bar{3}\) symmetry. The hole concentration increases with elevating Fe substitution level. Compared with those ambient-Pressure synthesized Fe-substituted CoSb3 samples, our samples exhibit enhanced power factor and suppressed thermal conductivity which benefitted from High Pressure. The optimal Co3.2Fe0.8Sb12 shows a peak ZT of 0.53 at 823 K, the Highest value for Co-rich p-type skutterudites with single-element substitution. Current study on Co4−xFexSb12 provides a basis for further thermoelectric performance enhancement of Co-rich p-type skutterudites.
Tadashi Sekiya - One of the best experts on this subject based on the ideXlab platform.
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High-Pressure Synthesis and ferroelectric properties in perovskite-type BiScO3–PbTiO3 solid solution
Journal of Applied Physics, 2004Co-Authors: Yoshiyuki Inaguma, Atsushi Miyaguchi, Masashi Yoshida, Tetsuhiro Katsumata, Yoshiro Shimojo, Ruiping Wang, Tadashi SekiyaAbstract:Stabilization of a perovskite-type solid solution (1−x) PbTiO3–x BiScO3 with x⩾0.45 was demonstrated by High-Pressure Synthesis, and the phase diagram and the ferroelectric properties of the solid solution were investigated. The crystal symmetry of the perovskite subcell change in turn from tetragonal, to rhombohedral, to pseudocubic, to monoclinic, and then to triclinic as x increases. It was found that the tetragonal, rhombohedral, and pseudocubic phases are ferroelectric, while the monoclinic phase is not. In the morphotropic phase boundary in the vicinity of x=0.37 between tetragonal and rhombohedral phases, the maximum electromechanical coupling factor and the minimum coercive electric field were just like those observed in other Pb-based ferroelectric perovskites. In addition, relaxor behavior in the dielectric constant was observed in the vicinity of x=0.5.
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High Pressure Synthesis and ferroelectric properties in perovskite type bisco3 pbtio3 solid solution
Journal of Applied Physics, 2004Co-Authors: Yoshiyuki Inaguma, Atsushi Miyaguchi, Masashi Yoshida, Tetsuhiro Katsumata, Yoshiro Shimojo, Ruiping Wang, Tadashi SekiyaAbstract:Stabilization of a perovskite-type solid solution (1−x) PbTiO3–x BiScO3 with x⩾0.45 was demonstrated by High-Pressure Synthesis, and the phase diagram and the ferroelectric properties of the solid solution were investigated. The crystal symmetry of the perovskite subcell change in turn from tetragonal, to rhombohedral, to pseudocubic, to monoclinic, and then to triclinic as x increases. It was found that the tetragonal, rhombohedral, and pseudocubic phases are ferroelectric, while the monoclinic phase is not. In the morphotropic phase boundary in the vicinity of x=0.37 between tetragonal and rhombohedral phases, the maximum electromechanical coupling factor and the minimum coercive electric field were just like those observed in other Pb-based ferroelectric perovskites. In addition, relaxor behavior in the dielectric constant was observed in the vicinity of x=0.5.
Oleksandr O. Kurakevych - One of the best experts on this subject based on the ideXlab platform.
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Nature of Hexagonal Silicon Forming via High-Pressure Synthesis: Nanostructured Hexagonal 4H Polytype.
Nano letters, 2018Co-Authors: Silvia Pandolfi, Yann Le Godec, Carlos Renero-lecuna, Benoit Baptiste, Nicolas Menguy, Michele Lazzeri, Christel Gervais, Kristina Spektor, Wilson A. Crichton, Oleksandr O. KurakevychAbstract:Hexagonal Si allotropes are expected to enhance light absorption in the visible range as compared to common cubic Si with diamond structure. Therefore, Synthesis of these materials is crucial for the development of Si-based optoelectronics. In this work, we combine in situ High-Pressure High-temperature Synthesis and vacuum heating to obtain hexagonal Si. High Pressure is one of the most promising routes to stabilize these allotropes. It allows one to obtain large-volume nanostructured ingots by a sequence of direct solid–solid transformations, ensuring High-purity samples for detailed characterization. Thanks to our Synthesis approach, we provide the first evidence of a polycrystalline bulk sample of hexagonal Si. Exhaustive structural analysis, combining fine-powder X-ray and electron diffraction, afforded resolution of the crystal structure. We demonstrate that hexagonal Si obtained by High-Pressure Synthesis correspond to Si-4H polytype (ABCB stacking) in contrast with Si-2H (AB stacking) proposed pre...
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Nature of Hexagonal Silicon Forming via High-Pressure Synthesis: Nanostructured Hexagonal 4H Polytype
Nano Letters, 2018Co-Authors: Silvia Pandolfi, Yann Le Godec, Carlos Renero-lecuna, Benoit Baptiste, Nicolas Menguy, Michele Lazzeri, Christel Gervais, Kristina Spektor, Wilson Crichton, Oleksandr O. KurakevychAbstract:Hexagonal Si allotropes are expected to enhance light absorption in the visible range as compared to common cubic Si with diamond structure. Therefore, Synthesis of these materials is crucial for the development of Si-based optoelectronics. In this work, we combine in situ High-Pressure High-temperature Synthesis and vacuum heating to obtain hexagonal Si. High Pressure is one of the most promising routes to stabilize these allotropes. It allows one to obtain large-volume nanostructured ingots by a sequence of direct solid–solid transformations, ensuring High-purity samples for detailed characterization. Thanks to our Synthesis approach, we provide the first evidence of a polycrystalline bulk sample of hexagonal Si. Exhaustive structural analysis, combining fine-powder X-ray and electron diffraction, afforded resolution of the crystal structure. We demonstrate that hexagonal Si obtained by High-Pressure Synthesis correspond to Si-4H polytype (ABCB stacking) in contrast with Si-2H (AB stacking) proposed previously. This result agrees with prior calculations that predicted a Higher stability of the 4H form over 2H form. Further physical characterization, combining experimental data and ab initio calculations, have shown a good agreement with the established structure. Strong photoluminescence emission was observed in the visible region for which we foresee optimistic perspectives for the use of this material in Si-based photovoltaics.
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Nature of Hexagonal Silicon Forming via High-Pressure Synthesis: Nanostructured Hexagonal 4H Polytype
Nano Letters, 2018Co-Authors: Silvia Pandolfi, Yann Le Godec, Carlos Renero-lecuna, Benoit Baptiste, Nicolas Menguy, Michele Lazzeri, Christel Gervais, Kristina Spektor, Wilson Crichton, Oleksandr O. KurakevychAbstract:Hexagonal Si allotropes are expected to enhance light absorption in the visible range as compared to common cubic Si with diamond structure. Therefore, Synthesis of these materials is crucial for the development of Si-based optoelectronics. In this work, we combine in situ High-Pressure High-temperature Synthesis and vacuum heating to obtain hexagonal Si. High Pressure is one of the most promising routes to stabilize these allotropes. It allows one to obtain large-volume nanostructured ingots by a sequence of direct solid–solid transformations, ensuring High-purity samples for detailed characterization. Thanks to our Synthesis approach, we provide the first evidence of a polycrystalline bulk sample of hexagonal Si. Exhaustive structural analysis, combining fine-powder X-ray and electron diffraction, afforded resolution of the crystal structure. We demonstrate that hexagonal Si obtained by High-Pressure Synthesis correspond to Si-4H polytype (ABCB stacking) in contrast with Si-2H (AB stacking) proposed previously. This result agrees with prior calculations that predicted a Higher stability of the 4H form over 2H form. Further physical characterization, combining experimental data and ab initio calculations, have shown a good agreement with the established structure. Strong photoluminescence emission was observed in the visible region for which we foresee optimistic perspectives for the use of this material in Si-based photovoltaics.
Yann Le Godec - One of the best experts on this subject based on the ideXlab platform.
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High-Pressure Synthesis of superhard and ultrahard materials
Journal of Applied Physics, 2019Co-Authors: Yann Le Godec, Alexandre Courac, Vladimir L. SolozhenkoAbstract:A brief overview of the High-Pressure Synthesis of superhard and ultrahard materials is presented in this tutorial paper. Modern High-Pressure chemistry represents a vast exciting area of research which can lead to new industrially important materials with exceptional mechanical properties. This field is only just beginning to realize its huge potential, and the image of “terra incognita” is not misused. We focus on three facets of this expanding research field by detailing the following: (i) the most promising chemical systems to explore (i.e., “where to search”); (ii) the various methodological strategies for exploring these systems (i.e., “how to explore”); and (iii) the technological and conceptual tools to study the latter (i.e., “the research tools”). These three aspects that are crucial in this research are illustrated by examples of the recent results on High-Pressure–High-temperature Synthesis of novel super- and ultrahard phases (orthorhombic γ-B28, diamondlike BC5, rhombohedral B13N2, and cubic ternary B–C–N phases). Finally, some perspectives of this research area are briefly reviewed.A brief overview of the High-Pressure Synthesis of superhard and ultrahard materials is presented in this tutorial paper. Modern High-Pressure chemistry represents a vast exciting area of research which can lead to new industrially important materials with exceptional mechanical properties. This field is only just beginning to realize its huge potential, and the image of “terra incognita” is not misused. We focus on three facets of this expanding research field by detailing the following: (i) the most promising chemical systems to explore (i.e., “where to search”); (ii) the various methodological strategies for exploring these systems (i.e., “how to explore”); and (iii) the technological and conceptual tools to study the latter (i.e., “the research tools”). These three aspects that are crucial in this research are illustrated by examples of the recent results on High-Pressure–High-temperature Synthesis of novel super- and ultrahard phases (orthorhombic γ-B28, diamondlike BC5, rhombohedral B13N2, and cubic ...
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High-Pressure Synthesis of ultrahard materials
arXiv: Materials Science, 2019Co-Authors: Yann Le Godec, Alexandre Courac, Vladimir L. SolozhenkoAbstract:A brief overview on High-Pressure Synthesis of ultrahard materials is presented. Modern High-Pressure chemistry represents a vast exciting area of research which can lead to new industrially important materials with exceptional mechanical properties. This field is only just beginning to realize its huge potential, and the image of "terra incognita" is not misused. We focus on three facets of this expanding research field by detailing: (i) the most promising chemical systems to explore (i.e. "where to search"); (ii) the various methodological strategies for exploring these systems (i.e. "how to explore"); (iii) the technological and conceptual tools to study the latter (i.e. "the research tools"). These three aspects that are crucial in this research are illustrated by examples of the recent results on High Pressure - High temperature Synthesis of novel ultrahard phases (orthorhombic gamma-B28, diamond-like BC5, rhombohedral B13N2 and cubic ternary B-C-N phases). Finally, some perspectives of this research area are briefly reviewed.
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High-Pressure Synthesis of superhard and ultrahard materials
Journal of Applied Physics, 2019Co-Authors: Yann Le Godec, Alexandre Courac, Vladimir L. SolozhenkoAbstract:A brief overview on High-Pressure Synthesis of superhard and ultrahard materials is presented in this tutorial paper. Modern High-Pressure chemistry represents a vast exciting area of research which can lead to new industrially important materials with exceptional mechanical properties. This field is only just beginning to realize its huge potential, and the image of "terra incognita" is not misused. We focus on three facets of this expanding research field by detailing: (i) the most promising chemical systems to explore (i.e. "where to search"); (ii) the various methodological strategies for exploring these systems (i.e. "how to explore"); (iii) the technological and conceptual tools to study the latter (i.e. "the research tools"). These three aspects that are crucial in this research are illustrated by examples of the recent results on High Pressure-High temperature Synthesis of novel super-and ultrahard phases (orthorhombic γ-B 28 , diamond-like BC 5 , rhombohedral B13N2 and cubic ternary B-C-N phases). Finally, some perspectives of this research area are briefly reviewed.
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Nature of Hexagonal Silicon Forming via High-Pressure Synthesis: Nanostructured Hexagonal 4H Polytype.
Nano letters, 2018Co-Authors: Silvia Pandolfi, Yann Le Godec, Carlos Renero-lecuna, Benoit Baptiste, Nicolas Menguy, Michele Lazzeri, Christel Gervais, Kristina Spektor, Wilson A. Crichton, Oleksandr O. KurakevychAbstract:Hexagonal Si allotropes are expected to enhance light absorption in the visible range as compared to common cubic Si with diamond structure. Therefore, Synthesis of these materials is crucial for the development of Si-based optoelectronics. In this work, we combine in situ High-Pressure High-temperature Synthesis and vacuum heating to obtain hexagonal Si. High Pressure is one of the most promising routes to stabilize these allotropes. It allows one to obtain large-volume nanostructured ingots by a sequence of direct solid–solid transformations, ensuring High-purity samples for detailed characterization. Thanks to our Synthesis approach, we provide the first evidence of a polycrystalline bulk sample of hexagonal Si. Exhaustive structural analysis, combining fine-powder X-ray and electron diffraction, afforded resolution of the crystal structure. We demonstrate that hexagonal Si obtained by High-Pressure Synthesis correspond to Si-4H polytype (ABCB stacking) in contrast with Si-2H (AB stacking) proposed pre...
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Nature of Hexagonal Silicon Forming via High-Pressure Synthesis: Nanostructured Hexagonal 4H Polytype
Nano Letters, 2018Co-Authors: Silvia Pandolfi, Yann Le Godec, Carlos Renero-lecuna, Benoit Baptiste, Nicolas Menguy, Michele Lazzeri, Christel Gervais, Kristina Spektor, Wilson Crichton, Oleksandr O. KurakevychAbstract:Hexagonal Si allotropes are expected to enhance light absorption in the visible range as compared to common cubic Si with diamond structure. Therefore, Synthesis of these materials is crucial for the development of Si-based optoelectronics. In this work, we combine in situ High-Pressure High-temperature Synthesis and vacuum heating to obtain hexagonal Si. High Pressure is one of the most promising routes to stabilize these allotropes. It allows one to obtain large-volume nanostructured ingots by a sequence of direct solid–solid transformations, ensuring High-purity samples for detailed characterization. Thanks to our Synthesis approach, we provide the first evidence of a polycrystalline bulk sample of hexagonal Si. Exhaustive structural analysis, combining fine-powder X-ray and electron diffraction, afforded resolution of the crystal structure. We demonstrate that hexagonal Si obtained by High-Pressure Synthesis correspond to Si-4H polytype (ABCB stacking) in contrast with Si-2H (AB stacking) proposed previously. This result agrees with prior calculations that predicted a Higher stability of the 4H form over 2H form. Further physical characterization, combining experimental data and ab initio calculations, have shown a good agreement with the established structure. Strong photoluminescence emission was observed in the visible region for which we foresee optimistic perspectives for the use of this material in Si-based photovoltaics.
Yoshiyuki Inaguma - One of the best experts on this subject based on the ideXlab platform.
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High-Pressure Synthesis of CuBa2Ca3Cu4O10+δSuperconductor from Precursors Prepared by a Polymerized Complex Method
Japanese Journal of Applied Physics, 2011Co-Authors: Tomoya Aoba, Hisayuki Suematsu, Yoshiyuki Inaguma, Tetsuhiro Katsumata, Takeshi Bizen, Tsuneo Suzuki, Tadachika Nakayama, Koichi NiiharaAbstract:Samples of a CuBa2Ca3Cu4O10+δ superconductor were synthesized under a High Pressure of 5 GPa at 1100–1200 °C for 30 min using precursors produced by solid-state reaction and polymerized complex methods. Compared with the precursors prepared by the solid-state reaction method, the precursors produced by the polymerized complex method have low grain sizes. The superconductive transition temperature of the samples prepared using precursors made by the polymerized complex method was found to be 113 K. The volume fractions of the superconducting phase in the samples prepared using precursors made by the solid-state reaction and polymerized complex methods were 49 and 36%, respectively. From these results, precursors made by the polymerized complex method can be used in the High-Pressure Synthesis of superconductors similarly to those made by the solid-state reaction method.
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High-Pressure Synthesis and ferroelectric properties in perovskite-type BiScO3–PbTiO3 solid solution
Journal of Applied Physics, 2004Co-Authors: Yoshiyuki Inaguma, Atsushi Miyaguchi, Masashi Yoshida, Tetsuhiro Katsumata, Yoshiro Shimojo, Ruiping Wang, Tadashi SekiyaAbstract:Stabilization of a perovskite-type solid solution (1−x) PbTiO3–x BiScO3 with x⩾0.45 was demonstrated by High-Pressure Synthesis, and the phase diagram and the ferroelectric properties of the solid solution were investigated. The crystal symmetry of the perovskite subcell change in turn from tetragonal, to rhombohedral, to pseudocubic, to monoclinic, and then to triclinic as x increases. It was found that the tetragonal, rhombohedral, and pseudocubic phases are ferroelectric, while the monoclinic phase is not. In the morphotropic phase boundary in the vicinity of x=0.37 between tetragonal and rhombohedral phases, the maximum electromechanical coupling factor and the minimum coercive electric field were just like those observed in other Pb-based ferroelectric perovskites. In addition, relaxor behavior in the dielectric constant was observed in the vicinity of x=0.5.
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High Pressure Synthesis and ferroelectric properties in perovskite type bisco3 pbtio3 solid solution
Journal of Applied Physics, 2004Co-Authors: Yoshiyuki Inaguma, Atsushi Miyaguchi, Masashi Yoshida, Tetsuhiro Katsumata, Yoshiro Shimojo, Ruiping Wang, Tadashi SekiyaAbstract:Stabilization of a perovskite-type solid solution (1−x) PbTiO3–x BiScO3 with x⩾0.45 was demonstrated by High-Pressure Synthesis, and the phase diagram and the ferroelectric properties of the solid solution were investigated. The crystal symmetry of the perovskite subcell change in turn from tetragonal, to rhombohedral, to pseudocubic, to monoclinic, and then to triclinic as x increases. It was found that the tetragonal, rhombohedral, and pseudocubic phases are ferroelectric, while the monoclinic phase is not. In the morphotropic phase boundary in the vicinity of x=0.37 between tetragonal and rhombohedral phases, the maximum electromechanical coupling factor and the minimum coercive electric field were just like those observed in other Pb-based ferroelectric perovskites. In addition, relaxor behavior in the dielectric constant was observed in the vicinity of x=0.5.