scholarly journals Physical Insights on the Lattice Softening Driven Mid‐Temperature Range Thermoelectrics of Ti/Zr‐Inserted SnTe—An Outlook Beyond the Horizons of Conventional Phonon Scattering and Excavation of Heikes’ Equation for Estimating Carrier Properties

2021 ◽  
pp. 2101122
Author(s):  
Ahmad Rifqi Muchtar ◽  
Bhuvanesh Srinivasan ◽  
Sylvain Le Tonquesse ◽  
Saurabh Singh ◽  
Nugroho Soelami ◽  
...  
Keyword(s):  
Phonon Scattering ◽  
Temperature Range ◽  
Lattice Softening

The lattice thermal conductivity of silver alloys between 0.3 and 4°K

1965 ◽  
Vol 257 (1083) ◽  
pp. 385-407 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Copper Alloys ◽  
Mean Free Path ◽  
Copper Sample ◽  
Phonon Interaction ◽  
Temperature Range ◽  
Electron Phonon Interaction ◽  
Electrical Resistivities

The thermal and electrical conductivities of silver and copper alloys with high electrical resistivities were studied in the temperature range from 0.3 to 4 °K. The lattice thermal conductivity results were interpreted in terms of Pippard’s semi-classical theory of the electron-phonon interaction and good qualitative agreement between this theory and the measurements was obtained for the temperature range from 1 to 4 °K. Below 1 °K the thermal conductivity of most samples decreased much more rapidly than one would have expected if the phonon mean free path were limited by the electron-phonon interaction only. Other phonon scattering mechanisms were therefore postulated and the effects of phonon scattering from dislocations was studied both theoretically and experimentally. The increase in thermal resistance below 1 °K of most alloys was more rapid than the increase obtained theoretically for phonon-dislocation and phonon-boundary scattering. The thermal conductivity of a copper sample with a resistance ratio of about 85 was found to be anomalous below 1 °K as well, suggesting that both the phonons and the conduction electrons could contribute to the effect in the alloys.

scholarly journals Computationally Modelling the Use of Nanotechnology to Enhance the Performance of Thermoelectric Materials

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5096
Author(s):  
Peter Spriggs ◽  
Qing Wang
Keyword(s):  
High Temperature ◽  
Thermoelectric Materials ◽  
Phonon Scattering ◽  
Waste Heat ◽  
Global Climate ◽  
Computational Simulation ◽  
Electrical Energy ◽  
Maximum Efficiency ◽  
Temperature Range ◽  
Band Engineering

The increased focus on global climate change has meant that the thermoelectric market has received considerably more attention. There are many processes producing large amounts of waste heat that can be utilised to generate electrical energy. Thermoelectric devices have long suffered with low efficiencies, but this can be addressed in principle by improving the performance of the thermoelectric materials these devices are manufactured with. This paper investigates the thermoelectric performance of market standard thermoelectric materials before analysing how this performance can be improved through the adoption of various nanotechnology techniques. This analysis is carried out through the computational simulation of the materials over low-, mid- and high-temperature ranges. In the low-temperature range, through the use of nanopores and full frequency phonon scattering, Mg0.97Zn0.03Ag0.9Sb0.95 performed best with a ZT value of 1.45 at 433 K. Across the mid-temperature range a potentially industry leading ZT value of 2.08 was reached by AgSbTe1.85Se0.15. This was carried out by simulating the effect of band engineering and the introduction of dense stacking faults due to the addition of Se into AgSbTe2. AgSbTe1.85Se0.15 cannot be implemented in devices operating above 673 K because it degrades too quickly. Therefore, for the top 200 K of the mid-temperature range a PbBi0.002Te–15% Ag2Te nanocomposite performed best with a maximum ZT of 2.04 at 753 K and maximum efficiency of 23.27 at 813 K. In the high-temperature range, through the doping of hafnium (Hf) the nanostructured FeNb0.88Hf0.12Sb recorded the highest ZT value of 1.49 at 1273 K. This was closely followed by Fe1.05Nb0.75Ti0.25Sb, which recorded a ZT value of 1.31 at 1133 K. This makes Fe1.05Nb0.75Ti0.25Sb an attractive substitute for FeNb0.88Hf0.12Sb due to the much lower cost and far greater abundance of titanium (Ti) compared with hafnium.

scholarly journals Charge transport variation from Bloch–Grüneisen to Mott variable range hopping and transport change due to hydrogenation in Palladium thin films

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Adithya Jayakumar ◽  
Viney Dixit ◽  
Sarath Jose ◽  
Vinayak B. Kamble ◽  
D. Jaiswal-Nagar
Keyword(s):  
Thin Films ◽  
Charge Transport ◽  
Phonon Scattering ◽  
Systematic Investigation ◽  
Large Temperature ◽  
Variable Range Hopping ◽  
Hydrogen Atoms ◽  
Variable Range ◽  
Temperature Range ◽  
Different Response

AbstractWe report a systematic investigation of the differences in charge transport mechanism in ultra-thin nano-island like films of palladium with thickness varying between 5 nm and 3 nm. The thicker films were found to be metallic in a large temperature range with a dominant Bloch–Grüneisen mechanism of charge transport arising due to electron-acoustic phonon scattering. These films were also found to exhibit an additional electron–magnon scattering. At temperatures below 20 K, the two films displayed a metal-insulator transition which was explained using Al’tshuler’s model of increased scattering in disordered conductors. The thinner films were insulating and were found to exhibit Mott’s variable range hopping mechanism of charge transport. The thinnest film showed a linear decrease of resistance with an increase in temperature in the entire temperature range. The island-like thin films were found to display very different response to hydrogenation at room temperature where the metallic films were found to display a decrease of resistance while the insulating films were found to have an increase of resistance. The decrease of resistance was ascribed to a hydrogen induced lattice expansion in the thin films that were at the percolation threshold while the resistance increase to an increase in work function of the films due to an increased adsorption of the hydrogen atoms at the surface sites of palladium.

Thermal Conductance of Individual Single-Wall Carbon Nanotubes

2008 ◽  
Author(s):  
Michael T. Pettes ◽  
Li Shi
Keyword(s):  
Carbon Nanotubes ◽  
Thermal Resistance ◽  
Phonon Scattering ◽  
Thermal Conductance ◽  
Phonon Transport ◽  
Single Wall Carbon Nanotubes ◽  
Platinum Resistance ◽  
Contact Thermal Resistance ◽  
Single Wall Carbon ◽  
Temperature Range

This work presents an experimental study of phonon transport in individual suspended single-wall carbon nanotubes (SWCNTs). Through the use of a micro fabricated device consisting of two adjacent suspended membranes, each with a platinum resistance heater and thermometer, the thermal conductance of several individual SWCNTs has been directly measured over the temperature range of 100 to 490 K. The effects of Umklapp phonon-phonon scattering remain weak and the thermal conductance remains roughly proportional to the calculated ballistic conductance throughout the temperature range. The macroscopic thermal conductance increases with temperature throughout the temperature range indicating static scattering processes or contact thermal resistance dominate transport in this regime. These results are an order of magnitude lower than the predicted ballistic thermal conductance calculated for a defect-free (18,0) nanotube. The results contrast with thermal conductance measurements reported using a high-bias DC self heating method. The discrepancy is discussed in terms of the differences in the contact thermal resistance, defects, and measurement methods.

ELASTIC ANOMALIES IN Y-123/Ag COMPOSITE MATERIALS

1995 ◽  
Vol 09 (23) ◽  
pp. 3053-3068 ◽  
Author(s):  
P. VENUGOPAL REDDY ◽  
S. SEKHER ◽  
V.N. MULAY
Keyword(s):  
Composite Materials ◽  
Ultrasonic Velocity ◽  
Sol Gel ◽  
Elastic Behavior ◽  
Qualitative Explanation ◽  
Temperature Range ◽  
Pulse Transmission ◽  
Transmission Technique ◽  
Elastic Anomalies ◽  
Lattice Softening

With a view to understand the influence of Ag on the microstructure of Y-123 samples, and hence its microstructural impact on the low temperature elastic behavior, a series of Y-123/Ag superconducting composite materials have been prepared by the Sol-Gel method. After characterization, ultrasonic velocity and attenuation measurements were undertaken over a temperature range of 80–300 K, using the pulse transmission technique. In contrast to the normal solids, the ultrasonic velocity of all the samples of the present investigation, in the temperature range of 80–300 K, are found to exhibit elastic anomalies signaling the presence of lattice instabilities. It has also been observed that most of the samples are found to exhibit longitudinal attenuation peaks at temperatures 250 K, 170 K and 100 K. A qualitative explanation for the observed phenomena of both lattice softening and attenuation is given on the basis of microstructure and relaxation.

Defects in ion implanted silicon

1978 ◽  
Vol 36 (1) ◽  
pp. 386-387
Author(s):  
J.A. Lambert ◽  
P.S. Dobson
Keyword(s):  
Defect Structure ◽  
Dislocation Loops ◽  
Frank Loop ◽  
Burgers Vector ◽  
Temperature Range ◽  
Perfect Dislocation ◽  
Contrast Analysis ◽  
Image Position ◽  
Ion Implanted

The defect structure of ion-implanted silicon, which has been annealed in the temperature range 800°C-1100°C, consists of extrinsic Frank faulted loops and perfect dislocation loops, together with‘rod like’ defects elongated along <110> directions. Various structures have been suggested for the elongated defects and it was argued that an extrinsically faulted Frank loop could undergo partial shear to yield an intrinsically faulted defect having a Burgers vector of 1/6 <411>.This defect has been observed in boron implanted silicon (1015 B+ cm-2 40KeV) and a detailed contrast analysis has confirmed the proposed structure.

Towards quantitative simulations of inelastic electron diffraction patterns and images

1992 ◽  
Vol 50 (2) ◽  
pp. 1170-1171
Author(s):  
Z. L. Wang
Keyword(s):  
Phonon Scattering ◽  
Incident Beam ◽  
Dynamical Theory ◽  
Inelastic Electron ◽  
Additional Advantage ◽  
Coupled Equations ◽  
Atomic Vibrations ◽  
Diffraction Patterns ◽  
Primary Advantage ◽  
The One

A new dynamical theory has been developed based on Yoshioka's coupled equations for describing inelastic electron scattering in thin crystals. Compared to existing theories, the primary advantage of this theory is that the incoherent summation of the diffracted intensities contributed by electrons after exciting vast numbers of different excited states has been evaluated before any numerical calculation. An additional advantage is that the phase correlations of atomic vibrations are considered, so that full lattice dynamics can be combined in the phonon scattering calculation. The new theory has been proven to be equivalent to the inelastic multislice theory, and has been applied to calculate energy-filtered diffraction patterns and images formed by phonon, single electron and valence scattered electrons.A calculated diffraction pattern of elastic and phonon scattered electrons for a parallel incident beam case is in agreement with the one observed (Fig. 1), showing thermal diffuse scattering (TDS) streaks and Kikuchi pattern.

Domain coarsening by grain boundary migration in ordered Ni4Mo

1986 ◽  
Vol 44 ◽  
pp. 560-561
Author(s):  
K. Vasudevan ◽  
H. P. Kao ◽  
C. R. Brooks ◽  
E. E. Stansbury
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Short Range ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Rapid Cooling ◽  
Temperature Range ◽  
Fee Structure ◽  
Domain Coarsening ◽  
Boundary Reaction

The Ni4Mo alloy has a short-range ordered fee structure (α) above 868°C, but transforms below this temperature to an ordered bet structure (β) by rearrangement of atoms on the fee lattice. The disordered α, retained by rapid cooling, can be ordered by appropriate aging below 868°C. Initially, very fine β domains in six different but crystallographically related variants form and grow in size on further aging. However, in the temperature range 600-775°C, a coarsening reaction begins at the former α grain boundaries and the alloy also coarsens by this mechanism. The purpose of this paper is to report on TEM observations showing the characteristics of this grain boundary reaction.

The reaction of amorphous Ni-Nb films with Si in the presence of a native SiO2 layer

1990 ◽  
Vol 48 (4) ◽  
pp. 664-665
Author(s):  
N. Rozhanski ◽  
A. Barg
Keyword(s):  
High Temperature ◽  
Crystallization Temperature ◽  
Diffusion Barriers ◽  
Sio2 Layer ◽  
Si Substrate ◽  
Cross Sectional ◽  
Plan View ◽  
Temperature Range ◽  
Sputter Deposited

Amorphous Ni-Nb alloys are of potential interest as diffusion barriers for high temperature metallization for VLSI. In the present work amorphous Ni-Nb films were sputter deposited on Si(100) and their interaction with a substrate was studied in the temperature range (200-700)°C. The crystallization of films was observed on the plan-view specimens heated in-situ in Philips-400ST microscope. Cross-sectional objects were prepared to study the structure of interfaces.The crystallization temperature of Ni5 0 Ni5 0 and Ni8 0 Nb2 0 films was found to be equal to 675°C and 525°C correspondingly. The crystallization of Ni5 0 Ni5 0 films is followed by the formation of Ni6Nb7 and Ni3Nb nucleus. Ni8 0Nb2 0 films crystallise with the formation of Ni and Ni3Nb crystals. No interaction of both films with Si substrate was observed on plan-view specimens up to 700°C, that is due to the barrier action of the native SiO2 layer.

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