scholarly journals Thermoelectric Elements with Negative Temperature Factor of Resistance

2021 ◽  
Author(s):  
Yuri Bokhan
Keyword(s):  
Nonequilibrium Thermodynamics ◽  
Relaxation Times ◽  
Negative Temperature ◽  
Ceramic Materials ◽  
Temperature Factor ◽  
Carbonic Gas ◽  
A Charge

The method of manufacturing of ceramic materials on the basis of ferrites of nickel and cobalt by synthesis and sintering in controllable regenerative atmosphere is presented. As the generator of regenerative atmosphere the method of conversion of carbonic gas is offered. Calculation of regenerative atmosphere for simultaneous sintering of ceramic ferrites of nickel and cobalt is carried out. It is offered, methods of the dilated nonequilibrium thermodynamics to view process of distribution of a charge and heat along a thermoelement branch. The model of a thermoelement taking into account various relaxation times of a charge and warmth is constructed.

scholarly journals Influence of AlN and GaN Pulse Ratios in Thermal Atomic Layer Deposited AlGaN on the Electrical Properties of AlGaN/GaN Schottky Diodes

Coatings ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 489 ◽  
Author(s):  
Hogyoung Kim ◽  
Seok Choi ◽  
Byung Joon Choi
Keyword(s):  
Photoelectron Spectroscopy ◽  
Schottky Diodes ◽  
Charge Trapping ◽  
Negative Temperature ◽  
Atomic Layer ◽  
Algan Layer ◽  
Pulse Ratio ◽  
Current Voltage ◽  
Frenkel Emission ◽  
A Charge

Atomic layer deposited AlGaN with different AlN and GaN pulse ratios (2:1, 1:1, and 1:2) was used to prepare AlGaN/GaN Schottky diodes, and their current transport mechanisms were investigated using current–voltage (I–V) and capacitance–voltage (C–V) measurements. Under low reverse bias condition, the sample with the pulse ratio of 2:1 was explained by Poole–Frenkel emission and the negative temperature dependence for the sample with the pulse ratio of 1:2 was associated with the acceptor levels in the AlGaN layer. Fast interface traps at 0.24–0.29 eV were observed for the samples with the pulse ratios of 1:1 and 1:2, whereas bulk traps at ~0.34 eV were observed for the sample with the pulse ratio of 2:1. Higher trap densities were obtained from the C–V hysteresis measurements when the pulse ratios were 1:1 and 1:2, indicating the presence of a charge trapping interfacial layer. According to the X-ray photoelectron spectroscopy spectra, the pulse ratio of 2:1 was found to have less oxygen-related defects in the AlGaN layer.

scholarly journals Compositions and Chemical Bonding in Ceramics by Quantitative Electron Energy-Loss Spectrometry

1994 ◽  
Vol 332 ◽  
Author(s):  
J. Bentley ◽  
L.L Horton ◽  
C.J. Mchargue ◽  
S. Mckernan ◽  
C.B. Carter ◽  
...  
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Molecular Beam ◽  
Ceramic Materials ◽  
Diffusion Couples ◽  
Directionally Solidified ◽  
Electron Energy Loss Spectrometry ◽  
A Charge ◽  
Electron Energy Loss ◽  
Sic Film

ABSTRACTQuantitative electron energy-loss spectrometry was applied to a range of ceramic materials at a spatial resolution of <5 nm. Analysis of Fe L23 white lines indicated a low-spin state with a charge transfer of ∼1.5 electrons/atom onto the Fe atoms implanted into (amorphized) silicon carbide. Gradients of 2 to 5% in the Co:O stoichiometry were measured across 100-nm-thick Co3O4 layers in an oxidized directionally solidified CoO-ZrO2 eutectic, with the highest O levels near the ZrO2. The energy-loss near-edge structures were dramatically different for the two cobalt oxides: those for Co3O4 have been incorrectly ascribed to CoO in the published literature. Kinetically stabilized solid solubility occurred in an AIN-SiC film grown by low-temperature molecular beam epitaxy (MBE) on α(6H)-SiC, and no detectable interdiffusion occurred in couples of MBE-grown AIN on SiC following annealing at up to 1750°C. In diffusion couples of polycrystalline AIN on SiC, interfacial 8H sialon (aluminum oxy-nitride) and pockets of Si3N4-rich β'sialon in the SiC were detected.

scholarly journals Nonequilibrium Thermodynamics and Distributions Time to Achieve a Given Level of a Stochastic Process for Energy of System

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
V. V. Ryazanov
Keyword(s):  
Stochastic Process ◽  
Entropy Production ◽  
Exponential Distribution ◽  
Nonequilibrium Thermodynamics ◽  
Relaxation Times ◽  
Irreversible Thermodynamics ◽  
Statistical Distribution ◽  
Extended Irreversible Thermodynamics ◽  
Thermodynamic Relationships ◽  
Nonequilibrium Entropy

In a previous paper (Ryazanov (2011)) with the joint statistical distribution for the energy and lifetime (time to achieve a given level of a stochastic process for energy of system) to derive thermodynamic relationships, clarifying similar expressions of extended irreversible thermodynamics we used an exponential distribution of lifetime. In this paper, we explore a more realistic expression for the distribution of time to achieve a given level of a stochastic process for energy of system (or relaxation times or lifetimes), and we analyse how such distribution affects the corresponding expressions of nonequilibrium entropy, temperature, and entropy production.

scholarly journals Frequency and temperature dependence behaviour of impedance, modulus and conductivity of BaBi4Ti4O15 aurivillius ceramic

2014 ◽  
Vol 8 (3) ◽  
pp. 145-153 ◽  
Author(s):  
Tanmaya Badapanda ◽  
Ranjan Harichandan ◽  
Sudhasu Nayak ◽  
Avinna Mishra ◽  
Sahid Anwar
Keyword(s):  
Relaxation Times ◽  
Complex Impedance ◽  
Negative Temperature ◽  
Impedance Spectrum ◽  
Nyquist Plot ◽  
Dielectric Study ◽  
Complex Impedance Spectrum ◽  
Debye Relaxation ◽  
Positive Side ◽  
Different Temperatures

In this work, we report the dielectric, impedance, modulus and conductivity study of BaBi4Ti4O15 ceramic synthesized by solid state reaction. X-ray diffraction (XRD) pattern showed orthorhombic structure with space group A21am confirming it to be an m=4 member of the Aurivillius oxide. The frequency dependence dielectric study shows that the value of dielectric constant is high at lower frequencies and decreases with increase in frequency. Impedance spectroscopy analyses reveal a non-Debye relaxation phenomenon since relaxation frequency moves towards the positive side with increase in temperature. The shift in impedance peaks towards higher frequency side indicates conduction in material and favouring of the long rangemotion of mobile charge carriers. The Nyquist plot from complex impedance spectrum shows only one semicircular arc representing the grain effect in the electrical conduction. The modulus mechanism indicates the non-Debye type of conductivity relaxation in the material, which is supported by impedance data. Relaxation times extracted using imaginary part of complex impedance (Z??) and modulus (M??) were also found to follow Arrhenius law. The frequency dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated. The variation of DC conductivity exhibits a negative temperature coefficient of resistance behaviour.

Electrotransport on Surfaces and Interfaces

1971 ◽  
Vol 26 (1) ◽  
pp. 40-44 ◽  
Author(s):  
P Adam
Keyword(s):  
Experimental Data ◽  
Charge Carrier ◽  
Negative Temperature ◽  
Surface And Interface ◽  
Drift Term ◽  
Surfaces And Interfaces ◽  
Carrier Scattering ◽  
A Charge ◽  
Charge Carrier Scattering ◽  
The Relationship

AbstractA summary of possible mechanisms of surface and interface mass transport in the presence of an electric field and current, and a brief review of experimental data are presented. Emphasis has been given to the relationship between faceting on metal surfaces and a charge carrier flow. A theory for this is presented based on the theory of pure thermal faceting by Mullins 8. The cal­culated values of the effective charge show a negative temperature gradient and are close to one for reasonably high temperatures, proving that the “drift term” caused by charge carrier scattering is negligible

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

Stress-Induced Ordering in Y203-Stabilized Tetragonal Zr02

1985 ◽  
Vol 43 ◽  
pp. 222-223
Author(s):  
J. Y. Koo ◽  
M. P. Anderson
Keyword(s):  
Electron Diffraction ◽  
Ionic Conduction ◽  
Electron Diffraction Study ◽  
Ceramic Materials ◽  
Bright Field Image ◽  
Transformation Toughening ◽  
Ion Milling ◽  
Thin Foils ◽  
Carbon Coated ◽  
Convergent Beam

Tetragonal Zr02 has been used as a toughening phase in a large number of ceramic materials. In this system, complex diffraction phenomena have been observed and an understanding of the origin of the diffraction effects provides important information on the nature of transformation toughening, ionic conduction, and phase destabilization. This paper describes the results of an electron diffraction study of Y203-stabilized, tetragonal Zr02 polycrystals (Y-TZP).Thin foils from the bulk Y-TZP sample were prepared by careful grinding and cryo ion-milling. They were carbon coated and examined in a Philips 400T/FEG microscope. Fig. 1 shows a typical bright field image of the 100% tetragonal(t) Zr02. The tetragonal structure was identified by both bulk x-ray diffraction and convergent beam electron diffraction (Fig. 2. A local region within a t-Zr02 grain was subjected to an intense electron beam irradiation which caused partial martensitic transformation of the t-Zr02 to monoclinic(m) symmetry, Fig. 3 A.

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