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11.
Robert D. Schmidt Eldon D. Case Zayra Lobo Travis R. Thompson Jeffrey S. Sakamoto Xiao-Yuan Zhou Ctirad Uher 《Journal of Materials Science》2014,49(20):7192-7212
The thermoelectric skutterudite Ba0.3Co4Sb12 is a promising candidate for waste heat recovery applications. Recently, it was demonstrated that the addition of silver nanoparticles (AgNP) to Ba0.3Co4Sb12 increases both the thermoelectric figure of merit and electrical conductivity. This study is the first to examine the effect of AgNP addition on the material’s mechanical properties. This study also found that the Young’s modulus, E, shear modulus, G, and bulk modulus, B, decreased linearly with increasing volume fraction porosity, P. Resonant ultrasound spectroscopy was employed to measure the elastic moduli, and Vickers indentation was used to determine the hardness, H, and fracture toughness, K C. Trends in the mechanical properties as a function of grain size, porosity, and the AgNP are discussed in terms of the pertinent literature. While K C was independent of AgNP addition, porosity, and grain size, both E and H decreased linearly with increasing porosity. In addition, this study is the first to identify (i) the Ag3Sb phase formed and (ii) the enhanced densification that occurs when the AgNP is sintered with Ba0.3Co4Sb12 powders, where both effects are consistent with the eutectic and peritectic reactions observed in the binary phase diagram Ag–Sb. These eutectic/peritectic reactions may also be linked to the enhancement of electrical conductivity previously observed when Ag is added to Ba0.3Co4Sb12. Also, similar beneficial eutectic/peritectic reactions may be available for other systems where conductive particles are added to other antimonides or other thermoelectric systems. 相似文献
12.
XianLi Su Han Li QuanSheng Guo Xinfeng Tang Qingjie Zhang Ctirad Uher 《Journal of Electronic Materials》2011,40(5):1286-1291
n-Type CoSb2.875−x
Ge0.125Te
x
(x = 0.125 to 0.275) compounds with different Te contents have been synthesized by a melt–quench–anneal–spark plasma sintering
method, and the effects of Te content on the structure and thermoelectric properties have been investigated. The results show
that all specimens exhibited n-type conduction characteristics. The solubility limit of Te in CoSb2.875−x
Ge0.125Te
x
is found to be x = 0.25. The solubility of Te in CoSb3 is increased through charge compensation of the element Ge. The room-temperature carrier concentration N
p of CoSb2.875−x
Ge0.125Te
x
skutterudites increases with increasing Te content, and the compounds possess high power factors. The maximum power factor
of 3.89 × 10−3 W m−1 K−2 was obtained at 720 K for the CoSb2.625Ge0.125Te0.25 compound. The thermal conductivity decreases dramatically with increasing Te content due to strong point defect scattering.
The maximum value of the thermoelectric figure of merit ZT = 1.03 was obtained at 800 K for CoSb2.625Ge0.125Te0.25, benefiting from a lower thermal conductivity and a higher power factor. The figure of merit is competitive with values reported
for single-filled skutterudites. 相似文献
13.
We have investigated heat conduction of single crystal Ba1–xKxBiO3 in the temperature range of 2–300 K and in a magnetic field of up to 6 Tesla. Temperature dependence of thermal conductivity(T) reveals the participation of both electrons and phonons with their relative contributions that depend critically on the potassium doping concentration. Crystals underdoped with potassium (samples with higherT
c) exhibit a strong suppression of and a glass-like temperature dependence. In contrast, those with a higher potassium content (lowerT
c) show an increase as temperature decreases with a peak near 23 K. Field dependence of(H) is also very sensitive to the level of potassium doping. Crystals exhibiting a large phonon contribution show an initial drop in(H) at low fields followed by a minimum and then a slow rise to saturation as the field increases. The initial drop is due to the additional phonon scattering by magnetic vortices as the sample enters a mixed state. The high field behavior of(H), arising from a continuous break-up of Cooper pairs, exhibits scaling which suggests the presence of an unconventional superconducting gap structure in this material. 相似文献
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17.
The authors present an overview of tunable microwave and millimeter-wave bandpass filters realized in different technologies. Some general design principles are described. Recent progress in the performance of various tunable filters is reported. The authors survey magnetically tunable filters (ferrimagnetic resonance filters, magnetostatic-wave filters, evanescent waveguide filters, E -plane printed circuit filters), electronically tunable filters, and mechanically tunable filters. The typical performance parameters are summarized. This comparison shown that none of these devices can simultaneously satisfy all requirements for perfect tunable filters. For microwave systems where multioctave tuning is essential, a YIG filter is an obvious choice. In systems where the requirement of high power handling capability combined with low insertion loss, predominates, mechanically tunable filters and magnetically tunable E -plane filters are recommended. If the tuning speed is a crucial requirement, varactor-tuned filters or E -plane filters with ferrite toroids are devices of choice. For millimeter-wave design, the most promising structures are ferrimagnetic resonance filters utilizing hexagonal ferrite resonators or, up to 60 GHz, magnetically tunable E -plane printed circuit filters 相似文献
18.
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20.
Dongwang Yang Xianli Su Jun Li Hui Bai Shanyu Wang Zhi Li Hao Tang Kechen Tang Tingting Luo Yonggao Yan Jinsong Wu Jihui Yang Qingjie Zhang Ctirad Uher Mercouri G. Kanatzidis Xinfeng Tang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(40):2003730
The applications of mixed ionic–electronic conductors are limited due to phase instability under a high direct current and large temperature difference. Here, it is shown that Cu2Se is stabilized through regulating the behaviors of Cu+ ions and electrons in a Schottky heterojunction between the Cu2Se host matrix and in-situ-formed BiCuSeO nanoparticles. The accumulation of Cu+ ions via an ionic capacitive effect at the Schottky junction under the direct current modifies the space-charge distribution in the electric double layer, which blocks the long-range migration of Cu+ and produces a drastic reduction of Cu+ ion migration by nearly two orders of magnitude. Moreover, this heterojunction impedes electrons transferring from BiCuSeO to Cu2Se, obstructing the reduction reaction of Cu+ into Cu metal at the interface and hence stabilizes the β-Cu2Se phase. Furthermore, incorporation of BiCuSeO in Cu2Se optimizes the carrier concentration and intensifies phonon scattering, contributing to the peak figure of merit ZT value of ≈ 2.7 at 973 K and high average ZT value of ≈ 1.5 between 400 and 973 K for the Cu2Se/BiCuSeO composites. This discovery provides a new avenue for stabilizing mixed ionic–electronic conduction thermoelectrics, and gives fresh insights into controlling ion migration in these ionic-transport-dominated materials. 相似文献