Enhanced thermoelectric properties of N-type polycrystalline In4Se3-x compounds via thermally induced Se deficiency

2014 ◽  
Vol 07 (03) ◽  
pp. 1450025 ◽  
Author(s):  
Ran Zhao ◽  
Yu-Tian Shu ◽  
Fu Guo
Keyword(s):  
Thermoelectric Properties ◽  
Thermal History ◽  
Thermal Processing ◽  
Carrier Mobility ◽  
Figure Of Merit ◽  
Thermally Induced ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Se Deficiency ◽  
Surface Morphologies

In 4 Se 3-x compound is considered as a potential thermoelectric material due to its comparably low thermal conductivity among all existing ones. While most studies investigated In 4 Se 3-x thermoelectric properties by controlling selennium or other dopants concentrations, in the current study, it was found that even for a fixed initial In / Se ratio, the resulting In / Se ratio varied significantly with different thermal processing histories (i.e., melting and annealing), which also resulted in varied thermoelectric properties as well as fracture surface morphologies of In 4 Se 3-x polycrystalline specimens. Single phase polycrystalline In 4 Se 3-x compounds were synthesized by combining a sequence of melting, annealing, pulverizing, and spark plasma sintering. The extension of previous thermal history was observed to significantly improve the electrical conductivity (about 121%) and figure of merit (about 53%) of In 4 Se 3-x polycrystalline compounds. The extended thermal history resulted in the increase of Se deficiency (x) from 0.39 to 0.53. This thermally induced Se deficiency was observed to associate with increasing carrier mobility but decreasing concentration, which differs from the general trend observed for the initially adjusted Se deficiency at room temperature. Unusually large dispersed grains with nanosize layers were observed in specimens with the longest thermal history. The mechanism(s) by which previous thermal processing enhances carrier mobility and affect microstructural evolution are briefly discussed.

Fabrication of Bi-Te Based Thermoelectric Semiconductors by Using Hybrid Powders

2005 ◽  
Vol 297-300 ◽  
pp. 875-880
Author(s):  
Cheol Ho Lim ◽  
Ki Tae Kim ◽  
Yong Hwan Kim ◽  
Dong Choul Cho ◽  
Young Sup Lee ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Single Crystals ◽  
Thermoelectric Properties ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
Bending Strength ◽  
Mixing Ratio ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
P Type

P-type Bi0.5Sb1.5Te3 compounds doped with 3wt% Te were fabricated by spark plasma sintering and their mechanical and thermoelectric properties were investigated. The sintered compounds with the bending strength of more than 50MPa and the figure-of-merit 2.9×10-3/K were obtained by controlling the mixing ratio of large powders (PL) and small powders (PS). Compared with the conventionally prepared single crystal thermoelectric materials, the bending strength was increased up to more than three times and the figure-of-merit Z was similar those of single crystals. It is expected that the mechanical properties could be improved by using hybrid powders without degradation of thermoelectric properties.

scholarly journals Hf-Doping Effect on the Thermoelectric Transport Properties of n-Type Cu0.01Bi2Te2.7Se0.3

2020 ◽  
Vol 10 (14) ◽  
pp. 4875
Author(s):  
Jeong Yun Hwang ◽  
Sura Choi ◽  
Sang-il Kim ◽  
Jae-Hong Lim ◽  
Soon-Mok Choi ◽  
...  
Keyword(s):  
Carrier Mobility ◽  
Figure Of Merit ◽  
Phonon Scattering ◽  
Mass Difference ◽  
Solidification Process ◽  
Transport Parameters ◽  
Plasma Sintering ◽  
Thermoelectric Transport Properties ◽  
Spark Plasma ◽  
Melt Solidification

Polycrystalline bulks of Hf-doped Cu0.01Bi2Te2.7Se0.3 are prepared via a conventional melt-solidification process and subsequent spark plasma sintering technology, and their thermoelectric performances are evaluated. To elucidate the effect of Hf-doping on the thermoelectric properties of n-type Cu0.01Bi2Te2.7Se0.3, electronic and thermal transport parameters are estimated from the measured data. An enlarged density-of-states effective mass (from ~0.92 m0 to ~1.24 m0) is obtained due to the band modification, and the power factor is improved by Hf-doping benefitting from the increase in carrier concentration while retaining carrier mobility. Additionally, lattice thermal conductivity is reduced due to the intensified point defect phonon scattering that originated from the mass difference between Bi and Hf. Resultantly, a peak thermoelectric figure of merit zT of 0.83 is obtained at 320 K for Cu0.01Bi1.925Hf0.075Te2.7Se0.3, which is a ~12% enhancement compared to that of the pristine Cu0.01Bi2Te2.7Se0.3.

Enhanced Thermoelectric Properties of Mg2Si0.3Sn0.7 Compounds by Bi Doping

2014 ◽  
Vol 616 ◽  
pp. 174-177
Author(s):  
Mei Jun Yang ◽  
Qiang Shen ◽  
Lian Meng Zhang
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Doping Concentration ◽  
Single Phase ◽  
Doping Content ◽  
Maximum Value ◽  
Plasma Sintering ◽  
Bi Doping ◽  
Spark Plasma

The single phase of Bi-doped Mg2Si0.3Sn0.7compounds have been successfully fabricated by solid state reaction and spark plasma sintering (SPS). The effect of Bi doping concentration on the thermoelectric properties of Mg2Si0.3Sn0.7is investigated. The doping of Bi atom results in the increase of carrier concentrations and ensures the increase of electrical conductivity. Although the thermal conductivity and Seebeck coefficient shows a slight increase, the figure of merit of Mg2Si0.3Sn0.7compounds still increases with the increasing contents of Bi-doping. When Bi-doping content is 1.5at%, the Mg2Si0.3Sn0.7compound obtained the maximum value,ZT, is 1.03 at 640 K.

Study on Mechanisms of Rare Earth Elements on Improving Thermoelectric Properties of RExCo4Sb12

2011 ◽  
Vol 71-78 ◽  
pp. 3737-3740
Author(s):  
Ke Gao Liu ◽  
Jing Li
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Mechanical Alloy ◽  
Spark Plasma Sintering ◽  
Thermoelectric Properties ◽  
Rare Earth Element ◽  
Figure Of Merit ◽  
Earth Element ◽  
Plasma Sintering ◽  
Spark Plasma

It is the important way to improve thermoelectric properties of skutterudite materials by doping with rare earth elements. The mechanisms of improving properties of bulk RExCo4Sb12materials prepared by mechanical alloy and spark plasma sintering (MA-SPS) at 650°C were investigated by analyzing the composition, microstructure and atomic occupying locations. According the results it can be considered that the mechanism to improve the thermoelectric properties of rare earth elements is that rare earth element Ce in the samples mainly plays the doping role in reducing the resistivity of the sample and improving the conductivity, so that it makes the figure of merit ZT of samples increase significantly.

Effect of Oxygen Content on Thermoelectric Properties of Sintered Bi-Te Based Compounds

2004 ◽  
Vol 449-452 ◽  
pp. 905-908 ◽  
Author(s):  
Dong Choul Cho ◽  
Cheol Ho Lim ◽  
D.M. Lee ◽  
Seung Y. Shin ◽  
Chung Hyo Lee
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Oxygen Content ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Air Atmosphere ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Effect Of Oxygen

The n-type thermoelectric materials of Bi2Te2.7Se0.3 doped with SbI3 were prepared by spark plasma sintering technique. The powders were ball-milled in an argon and air atmosphere. Then, powders were reduced in H2 atmosphere. Effects of oxygen content on the thermoelectric properties of Bi2Te2.7Se0.3 compounds have been investigated. Seebeck coefficient, electrical resistivity and thermal conductivity of the sintered compound were measured at room temperature. It was found that the effect of atmosphere during the powder production was remarkable and thermoelectric properties of sintered compound were remarkably improved by H2 reduction of starting powder. The obtained maximum figure of merit was 2.4 x 10-3/K.

scholarly journals Development of Spark Plasma Syntering (SPS) technology for preparation of nanocrystalline p-type thermoelctrics based on (BiSb)2Te3

2020 ◽  
Vol 21 (4) ◽  
pp. 628-634
Author(s):  
O. Kostyuk ◽  
B. Dzundza ◽  
M. Maksymuk ◽  
V. Bublik ◽  
L. Chernyak ◽  
...  
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Antimony Telluride ◽  
Bismuth Antimony Telluride ◽  
Thermoelectric Figure ◽  
Temperature Range ◽  
Plasma Sintering ◽  
Different Temperatures ◽  
Spark Plasma ◽  
P Type

Bismuth antimony telluride is the most commonly used commercial thermoelectric material for power generation and refrigeration over the temperature range of 200–400 K. Improving the performance of these materials is a complected balance of optimizing thermoelectric properties. Decreasing the grain size of Bi0.5Sb1.5Te3 significantly reduces the thermal conductivity due to the scattering phonons on the grain boundaries. In this work, it is shown the advances of spark plasma sintering (SPS) for the preparation of nanocrystalline p-type thermoelectrics based on Bi0.5Sb1.5Te3 at different temperatures (240, 350, 400oC). The complex study of structural and thermoelectric properties of Bi0.5Sb1.5Te3 were presented. The high dimensionless thermoelectric figure of merit ZT ~ 1 or some more over 300–400 K temperature range for nanocrystalline p-type Bi0.5Sb1.5Te3 was obtained.

Preparation and Thermoelectric Properties of Bi Doped Ca3Co4O9 Based Thermoelectric Materials

2018 ◽  
Vol 783 ◽  
pp. 144-147
Author(s):  
Jing Wang ◽  
Qin Chen ◽  
Xia Chun Zhu ◽  
Seok Je Lee ◽  
Kyoung Woo Park ◽  
...  
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Phonon Scattering ◽  
Solid Phase ◽  
Solid Phase Reaction ◽  
Phase Reaction ◽  
Sintering Process ◽  
Spin Entropy ◽  
Plasma Sintering ◽  
Spark Plasma

Polycrystalline Ca3-xBixCo4O9 samples have been prepared by solid-phase reaction followed by spark plasma sintering process. The thermoelectric properties have been systematically investigated from room temperature to near 1000K. It is found that the change of the carrier concentration leads to the change of resistivity, which is mainly associated with doping induced point defect phonon scattering. The change of the thermal potential mainly comes from the spin entropy. In addition, polycrystalline Ca3-xBixCo4O9 had a maximum figure of merit of 0.30 at 973 K, which was about 50% higher than Ca3Co4O9. It indicated that doping approach can effectively improve the thermoelectric performance of Ca3Co4O9+δ-based material.

Preparation and Thermoelectric Properties of Bi-Doped Mg2Si Nanocomposites

2009 ◽  
Vol 66 ◽  
pp. 17-20 ◽  
Author(s):  
Mei Jun Yang ◽  
Wei Jun Luo ◽  
Qiang Shen ◽  
Hong Yi Jiang ◽  
Lian Meng Zhang
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Dimensionless Figure Of Merit ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Heavy Doping ◽  
Nanocomposite Structures

Nanocomposites and heavy doping both are regarded as effective way to improve materials’ thermoelectric properties. 0.7at% Bi-doped Mg2Si nanocomposites were prepared by spark plasma sintering. Results of thermoelectric properties tests show that the doping of Bi atom effectively improves the electrical conductivity of Mg2Si，and the nanocomposite structures are helpful to reduce thermal conductivity and increase Seebeck coefficient, hence improving the thermoelectric performance. A maximum dimensionless figure of merit of 0.8 is obtained for the Bi-doped Mg2Si nanocomposite with 50 wt % nanopowder inclusions at 823K, about 63% higher than that of Bi-doped Mg2Si sample without nanopowder inclusions and 119% higher than that of microsized Mg2Si sample without Bi-doped, respectively.

scholarly journals Is LiI a Potential Dopant Candidate to Enhance the Thermoelectric Performance in Sb-Free GeTe Systems? A Prelusive Study

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 643 ◽  
Author(s):  
Bhuvanesh Srinivasan ◽  
David Berthebaud ◽  
Takao Mori
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Power Factor ◽  
Figure Of Merit ◽  
Lattice Thermal Conductivity ◽  
Short Communication ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Plasma Sintering ◽  
Spark Plasma

As a workable substitute for toxic PbTe-based thermoelectrics, GeTe-based materials are emanating as reliable alternatives. To assess the suitability of LiI as a dopant in thermoelectric GeTe, a prelusive study of thermoelectric properties of GeTe1−xLiIx (x = 0–0.02) alloys processed by Spark Plasma Sintering (SPS) are presented in this short communication. A maximum thermoelectric figure of merit, zT ~ 1.2, was attained at 773 K for 2 mol% LiI-doped GeTe composition, thanks to the combined benefits of a noted reduction in the thermal conductivity and a marginally improved power factor. The scattering of heat carrying phonons due to the presumable formation of Li-induced “pseudo-vacancies” and nano-precipitates contributed to the conspicuous suppression of lattice thermal conductivity, and consequently boosted the zT of the Sb-free (GeTe)0.98(LiI)0.02 sample when compared to that of pristine GeTe and Sb-rich (GeTe)x(LiSbTe2)2 compounds that were reported earlier.

Thermoelectric Properties of La-doped BaSi2 and (Ba,Sr)Si2 Solid Solutions

2007 ◽  
Vol 1044 ◽  
Author(s):  
Kohsuke Hashimoto ◽  
Ken Kurosaki ◽  
Hiroaki Muta ◽  
Shinsuke Yamanaka
Keyword(s):  
Thermal Conductivity ◽  
Solid Solution ◽  
Electrical Resistivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Dimensionless Figure Of Merit ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
La Doped

AbstractWe studied the thermoelectric properties of BaSi2 and SrSi2. The polycrystalline samples were prepared by spark plasma sintering (SPS). The electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) were measured above room temperature. The maximum values of the dimensionless figure of merit (ZT) were 0.01 at 954 K for BaSi2 and 0.09 at 417 K for SrSi2. We tried to enhance the ZT values of BaSi2 and SrSi2 by prepareing and characterizing La-doped BaSi2 and (Ba,Sr)Si2 solid solution.

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