scholarly journals Thermoelectric Characteristics of A Single-Crystalline Topological Insulator Bi2Se3 Nanowire

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 819
Author(s):  
Dedi ◽  
Ping-Chung Lee ◽  
Pai-Chun Wei ◽  
Yang-Yuan Chen
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Surface States ◽  
Volume Ratio ◽  
Single Crystalline ◽  
Transmission Electron ◽  
Growth Method ◽  
Spin Orbit Interactions ◽  
Good Agreement ◽  
Strong Spin

The discovery of topological insulators (TIs) has motivated detailed studies on their physical properties, especially on their novel surface states via strong spin–orbit interactions. However, surface-state-related thermoelectric properties are rarely reported, likely because of the involvement of their bulk-dominating contribution. In this work, we report thermoelectric studies on a TI bismuth selenide (Bi2Se3) nanowire (NW) that exhibit a larger surface/volume ratio. Uniform single-crystalline TI Bi2Se3 NWs were successfully synthesized using a stress-induced growth method. To achieve the study of the thermoelectric properties of a nanowire (NW), including electrical conductivity (σ), Seebeck coefficient (S), and thermal conductivity (κ), a special platform for simultaneously performing all measurements on a single wire was designed. The properties of σ, S, and κ of a 200 nm NW that was well precharacterized using transmission electron microscope (TEM) measurements were determined using the four-probe method, the two-probe EMF across ∇T measurement, and the 3ω technique, respectively. The integrated TE properties represented by the figure of merit ZT (S2σT/κ) were found to be in good agreement with a theoretical study of Bi2Se3 NW.

Magnetic Quantum Oscillations from Surface States of Bi Nanowires

2011 ◽  
Vol 1350 ◽  
Author(s):  
L. A. Konopko ◽  
T. E. Huber ◽  
A. A. Nikolaeva
Keyword(s):  
Single Crystal ◽  
Low Temperatures ◽  
Surface States ◽  
Charge Carriers ◽  
Quantum Oscillations ◽  
Wide Range ◽  
Spin Orbit Interactions ◽  
Conducting Tube ◽  
Magnetic Quantum Oscillations ◽  
Strong Spin

ABSTRACTIn this work, we report the results of studies of the transverse magnetoresistance (MR) of single-crystal Bi nanowires with diameter d<80 nm. The single-crystal nanowire samples were prepared by the Taylor-Ulitovsky technique. Due to the semimetal-to-semiconductor transformation and high density of surface states with strong spin-orbit interactions, the charge carriers are confined to the conducting tube made of surface states. The non monotonic changes of transverse MR that are equidistant in a direct magnetic field were observed at low temperatures in a wide range of magnetic fields up to 14 T. The period of oscillations depends on the wire diameter d as for the case of longitudinal MR. An interpretation of transverse MR oscillations is presented.

Enhanced thermoelectric properties in nanowires of InAs modulated with multiple-stub structures

2019 ◽  
Vol 9 (5) ◽  
pp. 498-502
Author(s):  
Changning Pan ◽  
Jun He ◽  
Zhiming Liu ◽  
Kaixing Shi
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermal Conductance ◽  
Volume Ratio ◽  
Electronic Density ◽  
Energy Filtering ◽  
Carrier Energy ◽  
Inas Nanowires ◽  
Scattering Matrix Method ◽  
Phonon Thermal Conductance

The thermoelectric properties of InAs nanowires modulated with the multiple-stub structures are studied using the scattering-matrix method. Owing to the very large surface-to-volume ratio, both the phonon and electron transport sensitively depend on the geometric structure. Carrier energy filtering which locally distorts electronic density of states strongly enhances the thermopower. Thus optimized thermopower, together with the significant reduction of the phonon thermal conductance, yields the high thermoelectric figure of merit ZT to 0.3∼1.9.

scholarly journals Enhancement in thermoelectric properties due to Ag nanoparticles incorporated in Bi2Te3 matrix

2019 ◽  
Vol 10 ◽  
pp. 634-643 ◽  
Author(s):  
Srashti Gupta ◽  
Dinesh Chandra Agarwal ◽  
Bathula Sivaiah ◽  
Sankarakumar Amrithpandian ◽  
Kandasami Asokan ◽  
...  
Keyword(s):  
Thermoelectric Properties ◽  
Power Factor ◽  
Figure Of Merit ◽  
Transmission Electron ◽  
High Power Factor ◽  
Different Temperatures ◽  
High Figure ◽  
Filtering Effect ◽  
P Type ◽  
20 Nm

The present study aims to see the enhancement in thermoelectric properties of bismuth telluride (Bi2Te3) annealed at different temperatures (573 and 773 K) through silver (Ag) nano-inclusions (0, 2, 5, 10, 15 and 20 wt %). Transmission electron microscopy (TEM) images of Ag incorporated in Bi2Te3 annealed at 573 K shows tubular, pentagonal, trigonal, circular and hexagonal nanoparticles with sizes of 6–25 nm (for 5 wt % Ag ) and 7–30 nm (for 20 wt % Ag). Ag incorporated in Bi2Te3 annealed at 773 K shows mainly hexagonally shaped structures with particle sizes of 2–20 nm and 40–80 nm (for 5 wt % Ag) and 10–60 nm (for 20 wt % Ag). Interestingly, the samples annealed at 573 K show the highest Seebeck coefficient (S, also called thermopower) at room temperature (p-type behavior) for 5% Ag which is increased ca. five-fold in comparison to Ag-free Bi2Te3, whereas for samples with the same content (5% Ag) annealed at 773 K the increment in thermopower is only about three-fold with a 6.9-fold enhancement of the power factor (S 2σ). The effect of size and shape of the nanoparticles on thermoelectric properties can be understood on the basis of a carrier-filtering effect that results in an increase in thermopower along with a control over the reduction in electrical conductivity to maintain a high power factor yielding a high figure of merit.

scholarly journals Optical and Thermoelectric Properties of Surface-Oxidation Sensitive Layered Zirconium Dichalcogenides ZrS2−xSex (x = 0, 1, 2) Crystals Grown by Chemical Vapor Transport

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 327
Author(s):  
Thalita Maysha Herninda ◽  
Ching-Hwa Ho
Keyword(s):  
Single Crystals ◽  
Thermoelectric Properties ◽  
Surface States ◽  
Chemical Vapor ◽  
Surface Oxidation ◽  
Vapor Transport ◽  
Chemical Vapor Transport ◽  
X Ray ◽  
Transmission Electron ◽  
Work Structure

In this work, structure, optical, and thermoelectric properties of layered ZrS2−xSex single crystals with selenium composition of x = 0, 1, and 2 were examined. Single crystals of zirconium dichalcogenides layer compounds were grown by chemical vapor transport method using I2 as the transport agent. X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) results indicated that ZrS2−xSex (x = 0, 1, and 2) were crystalized in hexagonal CdI2 structure with one-layer trigonal (1T) stacking type. X-ray photoelectron and energy dispersive X-ray measurements revealed oxidation sensitive behavior of the chalcogenides series. Transmittance and optical absorption showed an indirect optical gap of about 1.78 eV, 1.32 eV, and 1.12 eV for the ZrS2−xSex with x = 0, 1, and 2, respectively. From the result of thermoelectric experiment, ZrSe2 owns the highest figure-of merit (ZT) of ~0.085 among the surface-oxidized ZrS2−xSex series layer crystals at 300 K. The ZT values of the ZrS2−xSex (x = 0, 1, and 2) series also reveal increase with the increase of Se content owing to the increase of carrier concentration and mobility in the highly Se-incorporated zirconium dichalcogenides with surface states.

Crystal structure and thermoelectric properties of ReSi1.75 silicide

2002 ◽  
Vol 753 ◽  
Author(s):  
J-J Gu ◽  
K. Kuwabara ◽  
K. Tanaka ◽  
H. Inui ◽  
M. Yamaguchi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Thermoelectric Properties ◽  
First Principles ◽  
Figure Of Merit ◽  
First Principles Calculation ◽  
Dimensionless Figure Of Merit ◽  
Transmission Electron ◽  
P Type ◽  
Very High

ABSTRACTThe crystal structure of the defect disilicide formed with Re (ReSi1.75) has been refined by transmission electron microscopy combined with first-principles calculation. The crystal structure is monoclinic with the space group Cm (mc44) due to an ordered arrangement of vacancies on Si sites in the underlying (parent) C11b lattice. The thermoelectric properties of ReSi1.75 are highly anisotropic. Its electrical conduction is of n-type when measure along [001] while it is of p-type when measured along [100]. Although the value of Seebeck coefficient along [100] is moderately high (150–200 μV/K), it is very high along [001] (250–300 μV/K). As a result, a very high value of dimensionless figure of merit (ZT) of 0.7 is achieved at 1073 K when measured along [001].

Thermoelectric properties of Ag-doped CuS nanocomposites synthesized by a facile polyol method

2018 ◽  
Vol 20 (8) ◽  
pp. 5926-5935 ◽  
Author(s):  
Tarachand Tarachand ◽  
S. Hussain ◽  
N. P. Lalla ◽  
Y.-K. Kuo ◽  
A. Lakhani ◽  
...  
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Polyol Method ◽  
Thermoelectric Figure Of Merit ◽  
Temperature Dependent ◽  
Thermoelectric Figure ◽  
Single Crystalline

Single crystalline hexagonal nanodisks (NDs) of covellite CuS and temperature dependent thermoelectric figure of merit of Ag-doped CuS nanocomposites.

Effects of Antimony on the Thermoelectric Properties of the Cubic Pb9.6SbyTe10−xSexMaterials

2005 ◽  
Vol 886 ◽  
Author(s):  
Pierre Ferdinand Poudeu Poudeu ◽  
Jonathan D'Angelo ◽  
Adam Downey ◽  
Robert Pcionek ◽  
Joseph Sootsman ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Low Thermal Conductivity ◽  
Intermediate Temperature Range ◽  
Transmission Electron

ABSTRACTThe thermoelectric properties of Pb9.6SbyTe10−xSexwere investigated in the intermediate temperature range of 300 – 700 K. The effect of the variation of Sb content (y) on the electronic properties of the materials is remarkable. Samples with compositions Pb9.6Sb0.2Te10−xSex(y = 0.2) show the best combination of low thermal conductivity with moderate electrical conductivity and thermopower. For Pb9.6Sb0.2Te8Se2(x = 2) a maximum figure of merit of ZT ∼ 1.1 was obtained around 700 K. This value is nearly 1.4 times higher than that of PbTe at 700 K. This enhancement of the figure of merit of Pb9.6Sb0.2Te8Se2derives from its extremely low thermal conductivity (∼0.7 at W/m.K at 700 K). High resolution transmission electron microscopy of Pb9.6Sb0.2Te10−xSexsamples shows broadly distributed Sb-rich nanocrystals, which may be the key feature responsible for the suppression of the thermal conductivity.

Thermoelectric Properties of Zr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01 half-Heusler Alloy with WO3 Inclusions

2010 ◽  
Vol 1267 ◽  
Author(s):  
Julien Pierre Amelie Makongo Mangan ◽  
Pravin Paudel ◽  
Dinesh Misra ◽  
Pierre F. P. Poudeu
Keyword(s):  
Electrical Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Lattice Thermal Conductivity ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Lower Figure ◽  
Synthesized Materials

AbstractZr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01 composites with various concentrations of WO3 inclusions were synthesized by mechanical alloying using high energy shaker mill. High density hot pressed pellets of the synthesized materials were characterized using powder X-ray diffraction and transmission electron microscopy and their thermoelectric properties were investigated in the temperature range from 300 to 750 K. The electrical conductivity of the composites at 300 K decreases from 2500 S/cm for 0 wt.% WO3 alloy to 2200 S/cm for the composite with 2 wt.% WO3 inclusion. The electrical conductivity of composites containing 5 wt.% and 10 wt.% WO3 inclusions showed sharp increases with increasing WO3 content. The electrical conductivity of the composites monotonically decreases with rising temperature. All samples showed n-type semiconducting behavior and the thermopower values decrease with increasing WO3 content. The lattice thermal conductivity of the composites increases with increasing WO3 content. However, these values are about 30% lower than that of Zr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01 alloy prepared by high temperature solid-state techniques. The synthesized composites showed lower figure of merit than the half-Heusler matrix due to large reduction in the thermopower values with increasing WO3 content.

Improvements of Thermoelectric Performances in AgSbTe2 System With in-situ Ag2Te Nano-Precipitations

2010 ◽  
Vol 1267 ◽  
Author(s):  
Shengnan Zhang ◽  
Shenghui Yang ◽  
Guangyu Jiang ◽  
Junjie Shen ◽  
Tiejun Zhu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
State Of The Art ◽  
Critical Component ◽  
Energy Filtering ◽  
Transmission Electron ◽  
Filtering Effect ◽  
The Relationship

AbstractAgSbTe2 is the critical component in both LAST-m and TAGS-x system, which are two state-of-the-art mid-temperature thermoelectric bulk nanocomposites. By adjusting the Ag2Te/Sb2Te3 ratio, Sb2Te3 and Ag2Te precipitated samples were obtained with x = 0.68 to 0.74 and x = 0.84 to 0.90 (x as in (Ag2Te)x/2(Sb2Te3)1-x/2), respectively. The single phased AgSbTe2 was obtained with the x value of 0.78 and 0.81, which is consistent of the previous results on the phase diagram of (Ag2Te)x(Sb2Te3)1-x system. Comparing the effect of the two different precipitates, Ag2Te are much effective for the improvements of thermoelectric properties in AgSbTe2 nanocomposites. Utilizing the high-resolution transmission electron microscopy, Ag2Te was observed as nanodots and nano-lamellae embedded in the AgSbTe2 matrix, which can be related to the energy filtering effect for the increase of Seebeck coefficient. The relationship among the composition, microstructure and thermoelectric properties was systematically studied. It can be noticed that the thermoelectric properties of AgSbTe2 system are very sensitive to the composition, especially at low temperature. The maximum figure of merit ZT value of 1.53 was obtained at 500 K for Ag0.84Sb1.16Te2.16 with 40% increase comparing with the single phased sample.

TEM observation of iron oxide pillars in montmorillonite

1990 ◽  
Vol 48 (4) ◽  
pp. 882-883
Author(s):  
H. Mori ◽  
Y. Murata ◽  
H. Yoneyama ◽  
H. Fujita
Keyword(s):  
Aqueous Solution ◽  
Iron Oxide ◽  
Fine Particles ◽  
Aqueous Suspension ◽  
Volume Ratio ◽  
Exchange Capacity ◽  
Nano Composites ◽  
Pillared Montmorillonite ◽  
Topographic Features ◽  
Transmission Electron

Recently, a new sort of nano-composites has been prepared by incorporating such fine particles as metal oxide microcrystallites and organic polymers into the interlayer space of montmorillonite. Owing to their extremely large specific surface area, the nano-composites are finding wide application[1∼3]. However, the topographic features of the microstructures have not been elucidated as yet In the present work, the microstructures of iron oxide-pillared montmorillonite have been investigated by high-resolution transmission electron microscopy.Iron oxide-pillared montmorillonite was prepared through the procedure essentially the same as that reported by Yamanaka et al. Firstly, 0.125 M aqueous solution of trinuclear acetato-hydroxo iron(III) nitrate, [Fe3(OCOCH3)7 OH.2H2O]NO3, was prepared and then the solution was mixed with an aqueous suspension of 1 wt% clay by continuously stirring at 308 K. The final volume ratio of the latter aqueous solution to the former was 0.4. The clay used was sodium montmorillonite (Kunimine Industrial Co.), having a cation exchange capacity of 100 mequiv/100g. The montmorillonite in the mixed suspension was then centrifuged, followed by washing with deionized water. The washed samples were spread on glass plates, air dried, and then annealed at 673 K for 72 ks in air. The resultant film products were approximately 20 μm in thickness and brown in color.

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