This paper derives, for thermo-electro-magnetic field, new, unifying partial differential equations that describe electric currents, thermal currents, the temperature distribution in semiconductors. The performance analysis on Peltier super cooling system in the presence of magnetic field are executed using the equations. As a result, it was shown that the cooling performance at liquid nitrogen temperature was well improved by the magnetic field.
The current lead is a key component in a superconducting magnet system. Yet heat conduction and ohmic heating of the current lead should be kept to a minimum for economic reasons and for the cryogenic stability of the system. High temperature superconducting materials (HTS) has recently been used to solve the contradiction in the current lead. A third generation current lead, called the Peltier current lead, is described. The Peltier current elementis a heat pump made of N-type and P-type semiconductors. The technology of the Peltier element can be applied with HTS current lead. Experiments with the Peltier current lead demonstrate the reduction of heat leak of 15 to 25%. Since the HTS and the semiconductor are made from Bi-based materials, for exapmle, Bi-2223 for HTS and BiTe (Sb) for the semiconductor, we might made a whole current lead from Bi-based material, and this is one of the functionally gradient material (FGM).
For generation of electric power based on plasma confinement devices or nuclear fusion reactors, it was proposed to apply the Nernst effect to semiconductors, which are called Nernst elements. The efficiency of this energy conversion depends on transport properties of the Nernst element. It is expected that high mobility semiconductors, for example InSb, are suitable for the Nernst elements. In order to measure transport coefficients of the Nernst elements, we developed the diagnostic system. On our experiment of n-InSb doped with Te, we have detected the Nernst Voltage of about 3mV in the magnetic field of 4 Tesla at 323K with the temperature gradient of 100K per 17mm. This measuring system will make a lot of contributions to finding and studying the Nernst elements.
Generation of electric power by the Nernst effect is a new application of a semiconductor. A key point of this new proposal is to find materials with a good figure of merit of the Nernst effect, which is called a Nernst element. We propose InSb as a candidate for the Nernst element, because an electron mobility of InSb is very high at room temperature. Transport coefficients of InSb between 100K and 400K are given by the Boltzmann equation with a parabolic two-band model for an acoustic-phonon scattering process. Maxwell-Boltzmann distribution function is used as a non-perturbed distribution function. Our formulations with these approximation give the same temperature dependence as experiments for conductivity, Hall coefficient, and thermoelectric power. It is concluded that the acoustic-phonon scattering process is dominant in this region. However the Nernst coefficient given by the Boltzmann equation with the above conditions is not coincident with the result of experiments. This is a future problem.
Potential barriers in solids are act as carrier energy filter. It has been shown the elimination of lower energetic carriers by potential barriers brings the improvement of thermoelectric figure of merit. The improvement of figure of merit depends on the scattering processes and it is also shown this method works most effectively for the materials, in which the acoustic phonon scattering is dominant. The distance between potential barriers is also estimated by calculating the energy relaxation length.
Bismuth tellurides have been studied for investigating their electronic structures by using the discrete variational X α method. The systems not only Bi2Te3 but also the Se or Sb substituted-Bi2Te3 were calculated with setting threekinds of cluster corresponding to the base structure of Bi2Te3; cluster C-1: Bi7Te6, cluster C-2: Bi6Te7 and cluster C-3: Bi3Te10. The conditions for the calculation are non-relative and relative theories, non-spin and the crystal group of C3V. The cleavage and bond strength of the Bi2Te3 structurewere cleared through the calculations. The Se substituted-Bi2Te3 led to the ionic structure of Bi2Te3 of the base material and to the n-type thermoelectricity. Furthermore, the substitution with Sb atom caused the positive charge with rather covalent bonding nature than that in Bi2Te3, leading to the p-type. The relativistic calculation significantly indicated the weaker bond of Te-Te which places related to the cleavage and the contribution of 5d electrons of Bi appeared in the higher energy level.
PbTe sintered materials and metal electrode-semiconductor joints were prepared by plasma-activated sintering (PAS). The undoped PbTe powder (particle size of -1mm) was used for p-type as the source material, while a mixture of 4000 molppm PbI2 (dopant) with the undoped powder for n-type. The large carrier concentration and low mobility resulted for the p-type sintered material, compared with data for the melt-grown undoped PbTe. As for the n-type, the carrier concentration was not fully controlled and the Hall mobility was less than those of melt grown crystals, which indicates that sintering period might be too short to assure a uniformity of doping. The sintering of the semiconductor powder and the joining of metal electrode-semiconductor were simultaneously made in the single PAS process. The Fe/SnTe/p-PbTe and Fe/n-PbTe joints were successful made from the inspections by optical microscope and electric potential measurements, which will lead us to conform a π-shaped thermoelectric device.
IrSb3 is a compound with skutterudite crystal structure (prototype CoAs3). It has been reported that the structure have a good potential for thermoelectric materials. We prepared samples of IrSb3 by solidification or sintering. Thermoelectric properties of the samples were discussed concerning with preparing process. High figure of merit is expected by using sintering process.
A brick having a function to convert directly waste heat to electric energy was made on an experimental basis. U-shaped β-FeSi2 thermocouples were manufactured by ordinary sintering technique and inserted into a firebrick using as furnace wall. To avoid damage of the thermocouples caused by thermalstress between the firebrick and the thermocouple at high temperature, the firebrick and the thermocouple having different thermal expansion coefficients were joined with a compound of (Al2O3, SiO2)-fiber and Al2O3-castable ceramics. Optimal thickness of the thermocouple to obtain maximum electric power from one brick was examined, and it was found to be 5mm. The maximum power of the thermocouple was 55mW when the brick was heated up to 1000°C by an electric furnace.
An AC method of simultaneous measurment for the Seebeck coefficient and the thermal conductivity is proposed. This method shortens measurement time compared with conventional methods. In this work, the thermoelectric properties of the SiC/Cu are measured by this method at room temperature. The Seebeck coefficient obtained by the AC method (1.4-4.9×10-4V/K) is comparable to the data obtained by the DC method (1.8-3.8×10-4V/K). The thermal conductivity obtained by the AC method (78-86W/mK) is in good agreement with the data obtained by the photo pyro electric (PPE) method using the poly vinyliden difloride (PVF2) as the transducer (53-80W/mK).
The single-electron device is a quantum effect device which operates by using the single electron tunneling created by a Coulomb blockade. In this analogy, we propose the single quantum flux device which operates by using the single quantum flux tunneling. The single quantum flux transistor consists of the ferromagnet-supercnductor-ferromagnet junction of the sandwich structure. In this paper, we consider the physical mechanisms that lie behind the single quantum flux tunneling, and advanced a theoretical analysis to control this device.
If residual stress states induced by shot peering are sufficiently stable, they lead to enhancements of fatigue life. On the other hand, relaxation of shot peening induced residual stresses occurs as a consequence of high temperatures, high tensile or compressive loading or high cyclic loading. Therefore, stability and relaxation of residual stresses are a topic of considerable interest in theory and practice. New results are presented and discussed concerning all three causes of residual stress relaxation mentioned above. Especially, the conventional models describing the relaxation behaviour are compared with improved models which have been developed in the last few years.
With the method of Acoustic Emission Measurement, it is shown that in the process of formation of intermetallic compounds during soldering Acoustic Emission Events (AEE) are generated. These acoustic emission events may be used to describe more exactly the formation of the interface between solid wire and liquid solder bath in the soldering process for the copper-tin system.
Methods of making electrodes with different type of electrode structures and different kinds of conducting powder were examined for Zr-based Laves-phase alloys. Quicker initial activation and higher discharge capacity were observed for non-spot-welded electrode where an alloy pellet was sandwiched by nickel nets and then by nickel plates having a hole (diameter: 15mm). Electrode using nickel conducting powder showed a little better electrode performance than that using copper powder.
The purpose of this study is to clarify the inter-visual-field transfer of leaning and the effects of auditory distraction on visual task performance with short display duration using a computer controlled tachistoscope. Linearly arranged slash characters with two different directions were used as the visual stimuli. The stimuli were displayed on the tachistscope screen for 8ms duration. After the screen was cleared, computer-generated random textures were displayed as a masking pattern. Subjects were instructed to discriminate the direction of stimuli, during task performance, radio news programs were presented through a headphone. Results showed no inter-visual-field skill transfer. With auditory distraction, task performance was lower than in the control condition. Visual perception mechanisms in visual learning process and related problems of cross modal interference were also discussed.
The experiment to deposit refractive thin films on semiconductor laser facets had been performed, in which adjustment of refractive index matching between semiconductor material and thin film material is very important and very difficult, since the former index is very high (3.5) and the latter must be √3.5, which should be synthesized by ECRsputtering.
The application of a semiconductor laser or an optical fiber to holographic interferometory has been tryed. We used a grating-external-cavity visible laser diode as a light source and an optical fiber as an optical path in optical system to make a hologram.. The obtained hologram show that this optical system fit sufficiently to make hologram.
The polarization state of the light beam is conveniently described by Stokes parameters. We constructed a four-detector photopolarimeter that can simultaneously determine all of the stokes parameters. The time required for the determination of polarization state of the light is 0.6msec.
The definition of the joint laxity is ambiguous. Practically, the joint laxity is evaluated by the Range of Motion (R.O.M.) and the feeling of stiffness during passive joint motion. But it is not clearly objective but rather complicated. For this reason, we attempted to objectively evaluate the joint laxity of wrist joints by originally developed apparatus. In this study, the wrist joints of five volunteers were examined both clinically by manual and objective by apparatus, and reported the validity and reproducibility by this measurement system.