Analytical expression of phonon-phonon scattering strength and its application to Ge and KCl in the low- and high-temperature regions

1977 ◽  
Vol 15 (2) ◽  
pp. 1219-1222 ◽  
Author(s):  
T. J. Singh ◽  
G. S. Verma
Keyword(s):  
High Temperature ◽  
Phonon Scattering ◽  
Analytical Expression ◽  
Scattering Strength

scholarly journals An optimization of inner structures of the drying chamber of high temperature pneumatic drum drier

2010 ◽  
pp. 101-116
Author(s):  
Radivoje Topic ◽  
Nenad Cupric ◽  
Aleksandar Dedic ◽  
Aleksandar Petrovic
Keyword(s):  
High Temperature ◽  
Cross Section ◽  
Current Position ◽  
Working Process ◽  
Analytical Expression ◽  
Drying Chamber ◽  
Chamber Diameter

In this paper an analysis of the influence of parameters of flights from inner drying chamber structure and drying chamber is given. The influence of the following parameters on dryer working process is analyzed: number, shape and width of flights, level of coverage of cross-section drying chamber by material, rpm and drying chamber diameter. In the analytical expression for determining the amount of material seized by a curved flight, depending on the current position of the flight during drum rotation, a new parameter is introduced, compared to expression for a rectilinear flight. The expanded analytical expression could be used for optimization.

A Model for the High Temperature Transport Properties of Heavily Doped P-Type Silicon-Germanium Alloys

1991 ◽  
Vol 234 ◽  
Author(s):  
Cronin B. Vining
Keyword(s):  
High Temperature ◽  
Transport Properties ◽  
Silicon Germanium ◽  
Phonon Scattering ◽  
Impurity Scattering ◽  
Long Wavelength ◽  
Type Silicon ◽  
Heavily Doped ◽  
P Type ◽  
Silicon Germanium Alloys

ABSTRACTA model is presented for the high temperature transport properties of large grain size, heavily doped p-type silicon-germanium alloys. Good agreement with experiment (±10%) is found by considering acoustic phonon and ionized impurity scattering for holes and phonon-phonon, point defect and hole-phonon scattering for phonons. Phonon scattering by holes is found to be substantially weaker than phonon scattering by electrons, which accounts for the larger thermal conductivity values of ptype silicon-germanium alloys compared to similarly doped n-type silicongermanium alloys. The relatively weak scattering of long-wavelength phonons by holes raises the possibility that p-type silicon-germanium alloys may be improved for thermoelectric applications by the addition of an additional phonon scattering mechanism which is effective on intermediate and long-wavelength phonons. Calculations indicate improvements in the thermoelectric figure of merit up to 40% may be possible by incorporating several volume percent of 20 Å radius inclusions into p-type silicon-germanium alloys.

THERMAL CONDUCTIVITY OF HIGH TEMPERATURE SUPERCONDUCTORS

1991 ◽  
Vol 05 (12) ◽  
pp. 2003-2035 ◽  
Author(s):  
MANUEL D. NUÑEZ REGUEIRO ◽  
DARÍO CASTELLO
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Transition Temperature ◽  
Phonon Scattering ◽  
High Temperature Superconductors ◽  
Low Energy ◽  
Disordered Materials ◽  
Superconducting Transition ◽  
Universal Pattern ◽  
Heat Carriers

We review and analyze the data on the thermal conductivity of both ceramic and single crystal samples of high temperature superconductors. A universal pattern can be extracted and interpreted in the following way: phonons are the main heat carriers in these materials, and in the high temperature range the thermal conductivity κ is almost constant due to phonon scattering against disorder; below the superconducting transition temperature κ increases as phonon scattering against carriers condensing into the superconducting state decreases and at still lower temperatures there is a region in which a T2 law is obeyed that most probably is due to resonant phonon scattering against low energy excitations, i.e. tunneling systems similar to those found in disordered materials. The origin of the relevant disorder is discussed.

THEORY OF THERMAL CONDUCTIVITY OF HIGH TEMPERATURE SUPERCONDUCTORS: A NEW APPROACH

2011 ◽  
Vol 25 (09) ◽  
pp. 663-678 ◽  
Author(s):  
VINOD ASHOKAN ◽  
B. D. INDU
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Phonon Scattering ◽  
High Temperature Superconductors ◽  
Relaxation Times ◽  
Impurity Scattering ◽  
Resonance Scattering ◽  
Perturbative Approach ◽  
Conductivity Curve ◽  
Line Widths

An ab initio formulation of relaxation times of various contributing processes have been observed with newer understanding in terms of electron and phonon line widths. This is dealt with the help of double time temperature-dependent Green's function via a non-perturbative approach using a crystal Hamiltonian which comprises of the effects of electrons, phonons, impurities, anharmonicities and interactions thereof. The frequency line widths is observed as an extremely sensitive quantity in the transport phenomena of high temperature superconductors (HTS) as a collection of a large number of scattering processes, namely: boundary scattering, impurity scattering, multi-phonon scattering, interference scattering, electron–phonon processes and resonance scattering. The behavior of electrons and phonons is then investigated to describe the thermal conductivity of a variety of HTS samples specially in the vicinity of transition temperature to successfully explain the spectacular dip region of thermal conductivity curve which was lacking in explanation earlier with a sound physical justification.

Electron Concentration and Mobility in Semimetallic CdO

1971 ◽  
Vol 49 (4) ◽  
pp. 435-440 ◽  
Author(s):  
F. P. Koffyberg
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Low Temperatures ◽  
Phonon Scattering ◽  
Hall Constant ◽  
Apparent Increase ◽  
Optical Phonon Scattering ◽  
Complete Ionization ◽  
Dominant Process ◽  
Donor States

Measurements of the Hall constant and mobility in the temperature range 81–1100 °K were carried out on n-type CdO single crystals with defect concentrations of 1.9–31.7 × 1018/cm3. Carrier concentrations were found to be independent of temperature, indicating complete ionization of the defect donors and semimetallic conduction. At high temperature the mobility appears to be limited by optical phonon scattering, while at low temperature ionized defect scattering is the dominant process. The apparent increase of the effective mass at low temperatures from 0.15 m0 to 0.45 m0 with increasing defect concentrations is ascribed to increasing nonparabolicity of the conduction band resulting from the addition of donor states to the band.

High-temperature thermoelectric transport behavior of the Al/γ-Al2O3interface: impact of electron and phonon scattering at nanoscale metal–ceramic contacts

2018 ◽  
Vol 20 (21) ◽  
pp. 14513-14524 ◽  
Author(s):  
Pabitra Narayan Samanta ◽  
Jerzy Leszczynski
Keyword(s):  
High Temperature ◽  
Transport Properties ◽  
Phonon Scattering ◽  
Thermoelectric Transport ◽  
Transport Behavior ◽  
Ballistic Electron ◽  
Metal Ceramic ◽  
Thermoelectric Transport Properties

Thermoelectric transport properties of the Al/γ-Al2O3interface have been assessed from the ballistic electron and phonon transmission at the nanoscale contacts.

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.

Disordered quasicrystals: diffuse scattering in decagonal Al–Ni–Fe

2004 ◽  
Vol 37 (5) ◽  
pp. 802-807 ◽  
Author(s):  
E. Weidner ◽  
F. Frey ◽  
J.-L. Lei ◽  
B. Pedersen ◽  
C. Paulmann ◽  
...  
Keyword(s):  
High Temperature ◽  
Diffuse Scattering ◽  
Phonon Scattering ◽  
Calculated Data ◽  
Good Match ◽  
Thermal Diffuse Scattering ◽  
Local Defects ◽  
Thermal Diffuse ◽  
General Appearance

High-resolution synchrotron data of near-Bragg diffuse scattering from decagonal Al71.5Ni23.5Fe5quasicrystals were recorded. A dominant phasonic origin is ruled out because of the absence of a significantG⊥dependence. An analysis solely in the frame of thermal diffuse scattering (TDS) theory (phonon scattering) showed a good match between experimental and calculated data in the quasiperiodic layers, but with an improbable ratio of elastic constants,c66/c11 = 4.0.In situhigh-temperature measurements up to 1000 K revealed an increase of the intensity distribution perpendicular to the scattering vectorG. Huang diffuse scattering (HDS) arising from quenched local defects has a general appearance that qualitatively reproduces the observed symmetry and anisotropy. An interpretation based on both TDS and HDS contributions is given.

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