scholarly journals Observation of enhanced thermopower due to spin fluctuation in weak itinerant ferromagnet

2019 ◽  
Vol 5 (2) ◽  
pp. eaat5935 ◽  
Author(s):  
Naohito Tsujii ◽  
Akinori Nishide ◽  
Jun Hayakawa ◽  
Takao Mori
Keyword(s):  
Power Factor ◽  
Waste Heat ◽  
Spin Fluctuation ◽  
Heusler Alloys ◽  
Magnetic Interaction ◽  
Weak Ferromagnetism ◽  
Thermoelectric Power Factor ◽  
Ferromagnetic Metals ◽  
Itinerant Ferromagnet ◽  
Increasing Demand

Increasing demand for higher energy efficiency calls for waste heat recovery technology. Thus, facilitating practical thermoelectric generation systems is strongly desired. One option is enhancing the thermoelectric power factor, S2/r, where S is the Seebeck coefficient and r is the electrical resistivity, although it is still challenging because of the trade-off between S and r. We demonstrate that enhanced S2/r can be achieved by incorporating magnetic interaction in ferromagnetic metals via the spin fluctuation arising from itinerant electrons. We show that electron-doped Heusler alloys exhibit weak ferromagnetism at TC near room temperature with a small magnetic moment. A pronounced enhancement around TC was observed, with a 20% improvement in the power factor from the case where spin fluctuation is suppressed by applying magnetic field. This result supports the merit of using spin fluctuation to further enhance thermoelectric properties and the potential to further probe correlations and synergy between magnetic and thermoelectric fields.

scholarly journals Synthesis and Characterization of Thermoelectric Co2XSn (X = Zr, Hf) Heusler Alloys

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 624
Author(s):  
Alessandro Difalco ◽  
Francesco Aversano ◽  
Stefano Boldrini ◽  
Alberto Ferrario ◽  
Marcello Baricco ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Curie Temperature ◽  
Seebeck Coefficient ◽  
Transport Properties ◽  
Power Factor ◽  
Electronic Transport ◽  
Waste Heat ◽  
Heusler Alloys ◽  
Secondary Phases ◽  
Electronic Transport Properties

In this work, we report the results of an experimental investigation on the synthesis, structure, microstructure, mechanical, electrical conductivity, and Seebeck coefficient of Co2XSn (X = Zr, Hf) alloys. In both the alloys, the main constituent is a full Heusler-type compound that coexists with small amounts of secondary phases. Both alloys show a rather high Vickers hardness (around 900 HV) and an indentation fracture toughness typical of ceramics (around 2 MPa·m1/2). The electronic transport properties of the two alloys were measured for the first time. The temperature dependence of both the Seebeck coefficient and the electrical conductivity of the two alloys shows a change in correspondence of the Curie temperature. The Seebeck coefficient reaches a constant plateau, while the electrical conductivities show a transition from metallic to semiconductor behavior. As a consequence, almost constant values of the power factor have been obtained for the power factor above the Curie temperature, which is promising for an efficient exploitation of thermal gradients of several hundreds of degree in waste heat harvesting applications. Finally, on the basis of results from this work and from the literature, the effect of the substitution of the X element on the electronic transport properties in the series Co2XSn (X = Ti, Zr, Hf) is discussed.

High Thermoelectric Power Factor Near Room Temperature in Full-Heusler Alloys

2009 ◽  
Vol 38 (7) ◽  
pp. 1221-1223 ◽  
Author(s):  
Eric J. Skoug ◽  
Chen Zhou ◽  
Yanzhong Pei ◽  
Donald T. Morelli
Keyword(s):  
Thermoelectric Power ◽  
Power Factor ◽  
Room Temperature ◽  
Heusler Alloys ◽  
Thermoelectric Power Factor ◽  
Full Heusler ◽  
Full Heusler Alloys

scholarly journals High thermoelectric power factor of pure and vanadium-alloyed chromium nitride thin films

2021 ◽  
pp. 102493
Author(s):  
M.A. Gharavi ◽  
D. Gambino ◽  
A. le Febvrier ◽  
F. Eriksson ◽  
R. Armiento ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermoelectric Power ◽  
Power Factor ◽  
Chromium Nitride ◽  
Thermoelectric Power Factor

scholarly journals Macroscopic weavable fibers of carbon nanotubes with giant thermoelectric power factor

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Natsumi Komatsu ◽  
Yota Ichinose ◽  
Oliver S. Dewey ◽  
Lauren W. Taylor ◽  
Mitchell A. Trafford ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Thermoelectric Power ◽  
Power Factor ◽  
Fermi Energy ◽  
Performance Enhancement ◽  
Thermoelectric Performance ◽  
Thermoelectric Power Factor ◽  
Large Power ◽  
Energy Tuning

AbstractLow-dimensional materials have recently attracted much interest as thermoelectric materials because of their charge carrier confinement leading to thermoelectric performance enhancement. Carbon nanotubes are promising candidates because of their one-dimensionality in addition to their unique advantages such as flexibility and light weight. However, preserving the large power factor of individual carbon nanotubes in macroscopic assemblies has been challenging, primarily due to poor sample morphology and a lack of proper Fermi energy tuning. Here, we report an ultrahigh value of power factor (14 ± 5 mW m−1 K−2) for macroscopic weavable fibers of aligned carbon nanotubes with ultrahigh electrical and thermal conductivity. The observed giant power factor originates from the ultrahigh electrical conductivity achieved through excellent sample morphology, combined with an enhanced Seebeck coefficient through Fermi energy tuning. We fabricate a textile thermoelectric generator based on these carbon nanotube fibers, which demonstrates high thermoelectric performance, weavability, and scalability. The giant power factor we observe make these fibers strong candidates for the emerging field of thermoelectric active cooling, which requires a large thermoelectric power factor and a large thermal conductivity at the same time.

Improved thermoelectric power factor achieved by energy filtering in ZnO:Mg/ZnO hetero-structures

2021 ◽  
Vol 721 ◽  
pp. 138537
Author(s):  
Anh Tuan Thanh Pham ◽  
Phuong Thanh Ngoc Vo ◽  
Hanh Kieu Thi Ta ◽  
Hoa Thi Lai ◽  
Vinh Cao Tran ◽  
...  
Keyword(s):  
Thermoelectric Power ◽  
Power Factor ◽  
Thermoelectric Power Factor ◽  
Energy Filtering

Enhanced thermoelectric power factor of Re-substituted higher manganese silicides with small islands of MnSi secondary phase

2015 ◽  
Vol 3 (40) ◽  
pp. 10500-10508 ◽  
Author(s):  
Xi Chen ◽  
Jianshi Zhou ◽  
John B. Goodenough ◽  
Li Shi
Keyword(s):  
Thermoelectric Power ◽  
Power Factor ◽  
Secondary Phase ◽  
Small Islands ◽  
Thermoelectric Power Factor ◽  
Higher Manganese Silicides ◽  
Quenching Method

A rhenium-substituted HMS sample with small islands of MnSi secondary phase has been prepared by the quenching method. Such unique microstructure leads to an enhanced thermoelectric power factor (PF) as compared to the samples prepared by other methods.

Rapid Synthesis of Bi Substituted Ca3Co4O9 by a Polyacrylamide Gel Method and its High-Temperature Thermoelectric Power Factor

2010 ◽  
Vol 434-435 ◽  
pp. 393-396 ◽  
Author(s):  
Ying Song ◽  
Qiu Sun ◽  
Li Rong Zhao ◽  
Fu Ping Wang
Keyword(s):  
High Temperature ◽  
Thermoelectric Power ◽  
Power Factor ◽  
Solid State Reaction Method ◽  
Polyacrylamide Gel ◽  
Measured Temperature ◽  
Thermoelectric Power Factor ◽  
Gel Method ◽  
Plasma Sintering ◽  
Polyacrylamide Gel Method

A series of polycrystalline (Ca1-xBix)3Co4O9 ( x = 0.0 ~ 0.075 ) powders were synthesized rapidly by a polyacrylamide gel method. The dense ceramics were fabricated using the spark plasma sintering ( SPS ) technique. Effects of Bi substitution on high temperature thermoelectric properties of Ca3Co4O9 were evaluated. Both the electrical conductivity and Seebeck coefficient increased with increasing Bi content up to x = 0.05, thus leading to an enhanced thermoelectric power factor. The Bi substituted sample with x = 0.05 obtained in this study has the highest thermoelectric power factor in the measured temperature range. It reaches 4.810-4 Wm-1K-2 at 700 °C, which is 26 % higher than that of Ca3Co4O9 without Bi substitution, and is by up to 15 % larger as compared to the Bi substituted sample synthesized by the solid state reaction method and the SPS technique due to the high chemical homogeneous powder prepared by the polyacrylamide gel method.

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