Detailed Theoretical Investigation and Comparison of the Thermal Conductivities of n- and p-type Bi2Te3 Based Alloys

2013 ◽  
Vol 1543 ◽  
Author(s):  
Ö. Ceyda Yelgel ◽  
Gyaneshwar P. Srivastava
Keyword(s):  
Thermal Conductivity ◽  
Theoretical Investigation ◽  
Total Thermal Conductivity ◽  
Type Alloy ◽  
Electron Hole ◽  
Temperature Range ◽  
Image Position ◽  
P Type ◽  
Type 3 ◽  
Thermal Conductivities

ABSTRACTIn this work we present a detailed theoretical investigation of the thermal conductivities of n-type 0.1 wt.% CuBr doped 85% Bi2Te3 - 15% Bi2Se3 and p-type 3 wt% Te doped 20% Bi2Te3 - %80 Sb2Te3 single crystals. The thermal conductivity contributions arising from carriers, electron-hole pairs and phonons are computed rigorously in the temperature range $300\,{\rm{K}}\, \le \,T\, \le \,500\,{\rm{K}}$. In agreement with available experimental measurements we theoretically find that the lowest total thermal conductivity is 3.15 W K−1 m−1 at 380 K for the n-type alloy and 1.145 W K−1 m−1 at 400 K for the p-type alloy. Stronger mass-defect scattering is found to be responsible for the lower thermal conductivity of the p-type alloy throughout the temperature range of the study.

Thermoelectric behaviour of p- and n- type Ti-Ni-Sn half Heusler alloy variants and their amorphous equivalents

2013 ◽  
Vol 1490 ◽  
pp. 33-40
Author(s):  
Song Zhu ◽  
Satish Vitta ◽  
Terry M. Tritt
Keyword(s):  
Thermal Conductivity ◽  
Seebeck Coefficient ◽  
Heusler Alloys ◽  
Strong Temperature Dependence ◽  
Total Thermal Conductivity ◽  
Temperature Range ◽  
Transport Behaviour ◽  
Increasing Temperature ◽  
P Type ◽  
Amorphous Phase Formation

ABSTRACTTi-Ni-Sn type half-Heusler alloys which have the versatility to be either p- or n-type depending on the type of substitution, have been synthesized and investigated in the present work. The added advantage of doping them with multiple elements is that they will be amenable to bulk amorphous phase formation. The hole doped alloys were predominantly single phase with a cubic structure, while the electron doped alloys were found to have minor additional phases. All the alloys exhibit extremely weak metallic-like or degenerate semiconductor transport behaviour in the temperature range 20 K to 1000 K. The resistivity of p-type alloys exhibits semi-metallic-to-semiconducting transition at ∼ 500 K while the n-type alloys exhibit a weak metallic-like behaviour in the complete temperature range. The Seebeck coefficient has strong temperature dependence with a maximum of 45 μV K−1 in the temperature range 600-700 K in the p-type alloys. The n-type alloys however exhibit a linear variation of the Seebeck coefficient with temperature. The total thermal conductivity of the alloys increases with increasing temperature without any peak at low temperatures indicating significant disorder induced scattering. The p-type alloys have the lowest thermal conductivity compared to the n-type alloys. These alloys become amorphous after pulsed laser deposition except one alloy which exhibits compensated transport behaviour.

Effects of Nb doping on thermoelectric properties of Zn4Sb3 at high temperatures

2009 ◽  
Vol 24 (2) ◽  
pp. 430-435 ◽  
Author(s):  
D. Li ◽  
H.H. Hng ◽  
J. Ma ◽  
X.Y. Qin
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
High Temperatures ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermoelectric Performance ◽  
Temperature Range ◽  
A Value ◽  
Nb Doping ◽  
Thermal Conductivities

The thermoelectric properties of Nb-doped Zn4Sb3 compounds, (Zn1–xNbx)4Sb3 (x = 0, 0.005, and 0.01), were investigated at temperatures ranging from 300 to 685 K. The results showed that by substituting Zn with Nb, the thermal conductivities of all the Nb-doped compounds were lower than that of the pristine β-Zn4Sb3. Among the compounds studied, the lightly substituted (Zn0.995Nb0.005)4Sb3 compound exhibited the best thermoelectric performance due to the improvement in both its electrical resistivity and thermal conductivity. Its figure of merit, ZT, was greater than the undoped Zn4Sb3 compound for the temperature range investigated. In particular, the ZT of (Zn0.995Nb0.005)4Sb3 reached a value of 1.1 at 680 K, which was 69% greater than that of the undoped Zn4Sb3 obtained in this study.

Thermoelectric Properties of Bi2Te3-ySey Bulk Materials Synthesized by Melting-Grinding Process

2018 ◽  
Vol 773 ◽  
pp. 145-151
Author(s):  
Min Soo Park ◽  
Gook Hyun Ha ◽  
Hye Young Koo ◽  
Yong Ho Park
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Thermal Characteristics ◽  
Grinding Process ◽  
Alloy Scattering ◽  
Temperature Range ◽  
P Type ◽  
Optimal Effect

The Bi–Te thermoelectric system shows an excellent figure of merit (ZT) near room temperature. Research on increasing the ZT value for n‑type Bi–Te is imperative because the thermoelectric properties of this compound are inferior to those of the p-type material. For this purpose, n-type Bi2Te3-ySey powders with various amounts of Se dopant (0.3 ≤ y ≤ 0.6) were synthesized by a vacuum melting-grinding process to improve the physical properties. The ZT value of the sintered bodies was investigated in the temperature range of 298–423 K with regard to the electrical and thermal characteristics. As the Se content increased, the electrical conductivity decreased owing to a reduction in the carrier concentration, which improved the overall value of ZT. The thermal conductivity clearly decreased as the Se content increased in the temperature range of 298–373 K due to increased alloy scattering, as well as a reduction in the lattice thermal conductivity caused by crystal grain boundary scattering. At room temperature, Bi2Te2.7Se0.3 (y = 0.3) exhibited the highest ZT of 0.85. At increased temperatures, the ZT value was highest for Bi2Te2.55Se0.45 (y = 0.45), indicating that the optimal effect of the Se dopants varies depending on the temperature range.

Thermal Expansion and Isotopic Composition Effects on Lattice Thermal Conductivities of Crystalline Silicon

2006 ◽  
Author(s):  
Yunfei Chen ◽  
Guodong Wang ◽  
Deyu Li ◽  
Jennifer R. Lukes
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Md Simulation ◽  
Lattice Thermal Conductivity ◽  
Mass Difference ◽  
Dynamics Simulation ◽  
Temperature Range ◽  
Simulation Results ◽  
Callaway Model ◽  
Thermal Conductivities

Equilibrium molecular dynamics simulation is used to calculate lattice thermal conductivities of crystal silicon in the temperature range from 400K to 1600K. Simulation results confirmed that thermal expansion, which resulted in the increase of the lattice parameter, caused the decrease of the lattice thermal conductivity. The simulated results proved that thermal expansion imposed another type resistance on phonon transport in crystal materials. Isotopic and vacancy effects on lattice thermal conductivity are also investigated and compared with the prediction from the modified Debye Callaway model. It is demonstrated in the MD simulation results that the isotopic effect on lattice thermal conductivity is little in the temperature range from 400K to 1600K for isotopic concentration below 1%, which implies the isotopic scattering on phonon due to mass difference can be neglected over the room temperature. The remove of atoms from the crystal matrix caused mass difference and elastic strain between the void and the neighbor atoms, which resulted in vacancy scattering on phonons. Simulation results demonstrated this mechanism is stronger than that caused by isotopic scattering on phonons due to mass difference. A good agreement is obtained between the MD simulation results of silicon crystal with vacancy defects and the data predicted from the modified Debye Callaway model. This conclusion is helpful to demonstrate the validity of Klemens' Rayleigh model for impurity scattering on phonons.

THERMAL CONDUCTIVITY OF METALS AT HIGH TEMPERATURES: I. DESCRIPTION OF THE APPARATUS AND MEASUREMENTS ON IRON

1947 ◽  
Vol 25a (6) ◽  
pp. 357-374 ◽  
Author(s):  
L. D. Armstrong ◽  
T. M. Dauphinee
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
High Temperatures ◽  
Armco Iron ◽  
Absolute Error ◽  
Cylindrical Sample ◽  
Comprehensive Analysis ◽  
Temperature Curve ◽  
Temperature Range ◽  
Thermal Conductivities

An apparatus for measuring the thermal conductivity of metals in the temperature range 0° to 800 °C. is described. The method utilizes unidirectional heat flow in a cylindrical sample in a vacuum. The advantages of the method are outlined and a comprehensive analysis of possible errors in the measurements is included. Measurements on Armco iron indicate that results with an absolute error of less than 2% may be obtained. The results of measurements on a sample of Armco iron gave thermal conductivities of 0.1819 c.g.s units at 0 °C. and 0.0698 c.g.s. units at 800 °C. A change in slope of the thermal conductivity–temperature curve was found at a temperature of approximately 375 °C., and is tentatively attributed to the presence of 0.03% nickel impurity.

scholarly journals Measurements of Thermal Parameters in Antarctic Snow and Firn

1985 ◽  
Vol 6 ◽  
pp. 100-104 ◽  
Author(s):  
Manfred A. Lance
Keyword(s):  
Thermal Conductivity ◽  
Strong Dependence ◽  
Grain Structure ◽  
Ice Shelf ◽  
Governing Parameter ◽  
Needle Probe ◽  
Antarctic Snow ◽  
Data Yield ◽  
Image Position ◽  
Thermal Conductivities

Values Of Effective thermal conductivities of snow and firn were obtained at Filchner Ice Shelf (Antarctica). We employed a transient line source method (a needle probe with a diameter of 1.6 mm) for conductivity determination, which allows quick measurements with high spatial resolution. Our data yield a linear relationship between effective thermal conductivity (lg keff) and density (p) of snowwhich implies a strong dependence of thermal conductivity on density for 0.24≤p≤0.42, Comparison of thermal conductivities and other snow pit data suggests that density alone is a poor measure of effective thermal conductivities of snow and firn. We propose that grain structure is probably the governing parameter in determining heat transport in the upper firn layers.

A Detailed Theoretical Study of the Thermal Conductivity of Bi2(Te0.85Se0.15)3 Single Crystals

2012 ◽  
Vol 1404 ◽  
Author(s):  
Ö. Ceyda Yelgel ◽  
Gyaneshwar P. Srivastava
Keyword(s):  
Thermal Conductivity ◽  
Single Crystals ◽  
Theoretical Investigation ◽  
Theoretical Study ◽  
Single Mode ◽  
Debye Model ◽  
Electron Hole ◽  
Electron Hole Pair ◽  
N Doping ◽  
Different Levels

ABSTRACTWe present a theoretical investigation of the thermal conductivity for n-type doped Bi2(Te0.85Se0.15)3 single crystals by using the Debye model within the single-mode relaxationtime approximation. A detailed account of alloy, electron-phonon, phonon-phonon and electron-hole pair (bipolar) interactions are included. Different levels (0.1 and 0.05 wt.%) of n-doping from CuBr and SbI3 dopants were considered. The calculated conductivity, by combining lattice (κ ph) and electronic bipolar (κ bp) contributions, successfully explains the experimental results obtained by Hyun et al. [J. Mat. Sci. 33 5595 (1998)]. The κ ph contribution was calculated using Srivastava’s scheme and the κ bp contribution was obtained by employing Price’s theory.

scholarly journals Thermal and Electronic Transport Properties of the Half-Heusler Phase ScNiSb

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1723 ◽  
Author(s):  
Karol Synoradzki ◽  
Kamil Ciesielski ◽  
Igor Veremchuk ◽  
Horst Borrmann ◽  
Przemysław Skokowski ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Small Magnitude ◽  
Single Phase Sample ◽  
Heusler Phase ◽  
Temperature Range ◽  
Arc Melting ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
P Type

Thermoelectric properties of the half-Heusler phase ScNiSb (space group F 4 ¯ 3m) were studied on a polycrystalline single-phase sample obtained by arc-melting and spark-plasma-sintering techniques. Measurements of the thermopower, electrical resistivity, and thermal conductivity were performed in the wide temperature range 2–950 K. The material appeared as a p-type conductor, with a fairly large, positive Seebeck coefficient of about 240 μV K−1 near 450 K. Nevertheless, the measured electrical resistivity values were relatively high (83 μΩm at 350 K), resulting in a rather small magnitude of the power factor (less than 1 × 10−3 W m−1 K−2) in the temperature range examined. Furthermore, the thermal conductivity was high, with a local minimum of about 6 W m−1 K−1 occurring near 600 K. As a result, the dimensionless thermoelectric figure of merit showed a maximum of 0.1 at 810 K. This work suggests that ScNiSb could be a promising base compound for obtaining thermoelectric materials for energy conversion at high temperatures.

Anisotropy of thermal conductance in near-ideal graphite

1965 ◽  
Vol 284 (1396) ◽  
pp. 17-31 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Basal Plane ◽  
Thermal Conduction ◽  
Theoretical Estimate ◽  
Thermal Conductance ◽  
Temperature Range ◽  
Neutron Damage ◽  
Plane Direction ◽  
Umklapp Scattering ◽  
Thermal Conductivities

Measurements of thermal conductivities of a number of pyrolytic graphites are reported in­cluding values for annealed, hot pressed graphite (IFPA 57). Thermal conductivities of IFPA 57 in both basal plane and c -axis directions approach the values for ideal graphite at higher tem­peratures. A theoretical estimate of the anisotropy of thermal conduction in ideal graphite in the temperature range where umklapp scattering predominates shows fair agreement with the present experimental value. Such defects as are normally present in well-oriented graphite produce comparatively little effect on the c -axis thermal conductivity and exposure to neutron damage has a much smaller effect in the direction of the c axis, than in the basal plane direction.

The Thermal Conductivity of Several Fluoride Glasses

1985 ◽  
Vol 61 ◽  
Author(s):  
K. A. McCarthy ◽  
H. H. Sample ◽  
M. B. Koss
Keyword(s):  
Thermal Conductivity ◽  
Strong Correlation ◽  
Preliminary Analysis ◽  
Fluoride Glass ◽  
Plateau Region ◽  
Fluoride Glasses ◽  
Fluorozirconate Glasses ◽  
Temperature Range ◽  
Beryllium Fluoride ◽  
Thermal Conductivities

ABSTRACTThe thermal conductivities of beryllium fluoride glass and a fluoroberyllate glass have been measured in the 2–100K temperature range. These results are compared with earlier results on fluorozirconate glasses. The “plateau” region is well-defined for both materials. The plateau-center conductivity for BeF2 glass is the lowest yet recorded for any glass; it is some three times lower than the fluoroberyllate glass and four times lower than the fluorozirconates. A preliminary analysis of the data show a strong correlation between plateau-center conductivity and average cation mass of the material.

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