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Takashi Goto

Bio: Takashi Goto is an academic researcher from Wuhan University of Technology. The author has contributed to research in topics: Chemical vapor deposition & Spark plasma sintering. The author has an hindex of 38, co-authored 691 publications receiving 8532 citations. Previous affiliations of Takashi Goto include Hohai University & Nagaoka University of Technology.


Papers
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Journal ArticleDOI
TL;DR: In this article, the lattice parameters increase linearly with Ba content, and the electrical conductivity increases with increasing the Ba filling fraction, reaching a maximum value of 1.1 for Ba0.24Co4Sb12 at 850 K.
Abstract: Barium-filled skutterudites BayCo4Sb12 with an anomalously large filling fraction of up to y=0.44 have been synthesized. The lattice parameters increase linearly with Ba content. Magnetic susceptibility data show that Ba0.44Co4Sb12 is paramagnetic, which implies that some of the Co atoms in BayCo4Sb12 have acquired a magnetic moment. The presence of the two different valence states of Co (Co3+ and Co2+) leads to the anomalously large barium filling fraction even without extra charge compensation. All samples show n-type conduction. The electrical conductivity increases with increasing the Ba filling fraction. The lattice thermal conductivity of BayCo4Sb12 is significantly depressed as compared to unfilled Co4Sb12. The dimensionless thermoelectric figure of merit, ZT, increases with increasing temperature reaching a maximum value of 1.1 for Ba0.24Co4Sb12 at 850 K.

393 citations

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TL;DR: In this paper, the effects of partial substitution of nickel by palladium on the thermoelectric properties of ZrNiSn-based half-Heusler compounds were investigated and it was shown that substitution of palladium for nickel results in a significant, beneficial reduction of the thermal conductivity.
Abstract: We report on the effects of partial substitution of nickel by palladium on the thermoelectric properties of ZrNiSn-based half-Heusler compounds. It is shown that the substitution of palladium for nickel results in a significant, beneficial reduction of the thermal conductivity. The Seebeck coefficient also decreases, but only by a small amount. In the Hf0.5Zr0.5Ni0.8Pd0.2Sn0.99Sb0.01 compound, a power factor of 22.1 μW K−2 cm−1 and a thermal conductivity as low as 4.5 W/m K are measured at room temperature. The dimensionless figure of merit ZT increases with increasing temperature and reaches a maximum value of 0.7 at about 800 K.

375 citations

Journal ArticleDOI
01 Nov 2015-Fuel
TL;DR: In this article, the authors investigated the characteristics of ammonia/air premixed flames at various pressures up to 0.5 MPa and found that the maximum value of unstretched laminar burning velocities is less than 7 cm/s within the examined conditions and is lower than those of hydrocarbon flames.

346 citations

Journal ArticleDOI
TL;DR: In this article, the structural, chemical, and transport properties of Yb2O3 composites are studied, and the maximum figures of merit reach 1.3 for the Yb 0.25Co4Sb12∕Yb 2O3 and 1.2 for Yb0.21Co 4Sb 12∕ Yb 2 O3 at 850K.
Abstract: Composites containing Yb-filled CoSb3 and well-distributed Yb2O3 particles are synthesized by in situ reaction method. The structural, chemical, and transport properties of the composites are studied. Some Yb2O3 particles with microsize locate at the grain boundaries of matrix and others distribute within YbyCo4Sb12 grains as nanoscale inclusions. The combination of the “rattling” of Yb ions inside the voids of CoSb3 and the phonon scattering of the oxide defects results in a remarkable reduction in the lattice thermal conductivity. The thermoelectric performance of the composites is significantly improved, and the maximum figures of merit reach 1.3 for the Yb0.25Co4Sb12∕Yb2O3 and 1.2 for the Yb0.21Co4Sb12∕Yb2O3 composites at 850K.

187 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the thermoelectric properties of single-phase RyMxCo4−xSb12 (x=0-3.0,y=0−0.7) compounds filled by Ce, Ba, and Y, and substituted by Fe and Ni.
Abstract: Single-phase RyMxCo4−xSb12(x=0–3.0,y=0–0.7) compounds filled by Ce, Ba, and Y, and substituted by Fe and Ni are synthesized by using the solid-state reaction method and melting reaction method. The structure and the thermoelectric properties of RyMxCo4−xSb12 are investigated systematically. The thermal parameter (B) of Ba and Ce filled in Sb-icosahedron voids in the skutterudite structure is larger than that of Sb and Co (Fe). The maximum filling fraction of Ce and Ba (ymax) for RyFexCo4−xSb12 increases with the increasing Fe content, and it is found that the maximum filling fraction of Ba (ymax) is greater than that of CeyFexCo4−xSb12. The filling atoms Ba, Ce, and Y in Sb-icosahedron voids can reduce the lattice thermal conductivity of RyMxCo4−xSb12 compounds remarkably, and the lattice thermal conductivity decreases in the order of ionic radii decreasing of Ba2+, Ce3+, and Y3+. When Ce and Ba filing fraction is 0.3–0.4, the lattice thermal conductivity of RyFexCo4−xSb12 compounds reaches a minimum valu...

138 citations


Cited by
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TL;DR: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties are equally important.
Abstract: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

6,852 citations

Journal ArticleDOI
TL;DR: In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented, ranging from atom to phase diagram, and the current development stage in lead free piezoceramics is then critically assessed.
Abstract: A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

2,510 citations

Journal ArticleDOI
TL;DR: The most promising bulk materials with emphasis on results from the last decade are described and the new opportunities for enhanced performance bulk nanostructured composite materials are examined and a look into the not so distant future is attempted.
Abstract: Herein we cover the key concepts in the field of thermoelectric materials research, present the current understanding, and show the latest developments. Current research is aimed at increasing the thermoelectric figure of merit (ZT) by maximizing the power factor and/or minimizing the thermal conductivity. Attempts at maximizing the power factor include the development of new materials, optimization of existing materials by doping, and the exploration of nanoscale materials. The minimization of the thermal conductivity can come through solid-solution alloying, use of materials with intrinsically low thermal conductivity, and nanostructuring. Herein we describe the most promising bulk materials with emphasis on results from the last decade. Single-phase bulk materials are discussed in terms of chemistry, crystal structure, physical properties, and optimization of thermoelectric performance. The new opportunities for enhanced performance bulk nanostructured composite materials are examined and a look into the not so distant future is attempted.

1,951 citations

Journal ArticleDOI
TL;DR: Heusler compounds as discussed by the authors are a remarkable class of intermetallic materials with 1:1:1 or 2:1-1 composition comprising more than 1500 members, and their properties can easily be predicted by the valence electron count.

1,675 citations