Magnitude Of Electrical Resistivity Research Articles

ДИЭЛЕКТРИКТЕРДІҢ ЭЛЕКТРЛІК БЕРІКТІГІ

Abstract. In human life, even in practice, solids play an important role. Metals, dielectrics, electrical engineering, semiconductors, electrons, magnets, conductors lying close to each other are all solids. It can be argued that the basis for the foundation of scientific and technological progress is a solid body. But in their study, not only practical activity mattered. For its subsystems of development, solid state physics has opened a scientific path to understanding the properties of importance. all materials used in engineering are divided into three groups: conductors, semiconductors and dielectrics. These materials differ in the magnitude of electrical resistance, the nature of its changes during heating and the type of conductivity.The electrical resistivity of the conductors is in the range of 10-6 + 10-3 oms • cm and is used as a material with a small intermediate electrical resistance for resistance elements, heating elements, contacts, etc. for conducting constant and rotational currents. Electrical resistivity of semiconductors 10-3+10+10 Om* is within cm and decreases when heated. They are used for rectification, amplification, conversion of various types of energy into electricity. Electrical resistivity of dielectrics 10+10+10+18 Oms* are within cm, they are used as insulators. The conductivity of solids is determined primarily by the electronic structure. In solids, as a result of the interaction of the electromagnetic field of atoms, energy electronic sublevels are classified with the formation of an energy zone [1]. With the transition to a higher energy, the width of the zone of permissible sublevels increases, and the zones intersect. When approaching the distance between atoms Forbidden energy zones even disappear. The density of the zones filled with electrons and their crosslinking determine the electrical conductivity of solids. Keywords: dielectric, composition, automation, electronics, radio engineering, aerospace, rocket, electrical, conductor.

Magnetic properties of [formula omitted]-based diluted magnetic semiconductors

Polycrystalline Sn 1− x Ni x O 2 samples were prepared in single-phase form for x = 0.02 and 0.07 and were characterized using several experimental techniques. Room-temperature ferromagnetism with transition temperature, T c , as high as 770 K was observed from the temperature variation of magnetization measurements. Nanoparticles of uniform crystalline phase and composition were identified from the transmission electron microscope images. The initial magnetization curves recorded at 80 and 300 K for both samples could be analyzed based on the bound magnetic polaron (BMP) model, where the size of the BMP is found to increase with temperature. The magnitude of electrical resistivity is found to decrease with doping, and its temperature dependence could be explained based on the variable range hopping mechanism.

Role of oxide barrier in intergranular tunnel junctions: An enhanced magnetoresistance in SiO2 and ZnO coated Fe3O4 nanoparticle compacts

A systematic study of oxide coated magnetic nanoparticles is carried out to understand and evaluate the effect of oxide tunnel barrier on the magnetoresistance (MR) of magnetite core-shell nanocompacts. SiO2 and ZnO coated Fe3O4 nanoparticles with a shell thickness of ∼2nm have been synthesized and characterized. Magnetic measurements on oxide coated Fe3O4 nanoparticles reveal blocking behavior and superparamagnetism below ∼200K. The magnitude of electrical resistivity at room temperature of SiO2 and ZnO coated Fe3O4 compacts is found to be two to five orders higher than that of pure nanocrystalline Fe3O4 compacts due to resulting insulating oxide layer between magnetite domains. For these nanocompacts, large low field magnetoresistances of −11.5% and −5.8% are achieved in an applied magnetic field of 1T at 100K that could have origins of spin-dependent tunnel MR across the nanometric granules of Fe3O4 safely embedded in insulating oxide matrix.

The effect of Al/Si ratio on the transport properties of the layered intermetallic compoundCaAl2Si2

We report the results of the electrical resistivity and Seebeck coefficientas well as thermal conductivity measurements on the stoichiometricCaAl2Si2 andnon-stoichiometric CaAl1.75Si2.25, CaAl1.9Si2.1,CaAl2.1Si1.9,and CaAl2.25Si1.75 compounds in the temperature range 10–300 K. It has been found that the magnitude ofelectrical resistivity decreases for the non-stoichiometric samples, attributed to the shift ofFermi energy from the dip of the density of states as a consequence of the changedSi/Al content. In addition, a systematic change in the magnitude of Seebeck coefficient as a function ofAl/Si concentration has been observed. The results have been associated with the effect ofhole/electron doping on the Fermi level density of states. A detailed analysisof the electrical resistivity and Seebeck coefficient suggests the presence of twotypes of charge carrier and the temperature dependent changes in their mobility.From the thermal conductivity results, we correlated the extent of disorder andAl/Si ratio with various thermal scattering mechanisms in the investigated temperature range.

Electronic properties of superconducting (YBa 2Cu 3O 6.9) 1−xAg x compounds

We have studied electronic properties of (YBa 2Cu 3O 6.9) 1−xAg x compounds with 5, 10, 15, 25 and 50 wt % Ag. In our samples, the silver fills the intergranular space and the superconducitivity is preserved even at 50 wt % Ag (Tc = 87 K). These samples can be safely droped in water without loss of superconductivity. The magnitude of electrical resistivity at 300 K rapidly decreases from 10 3 μΩcm for 5 wt % Ag down to ∽30 gmΩcm for 50 wt % Ag. The superconducting transition is always around 92 K. Preliminary measurements on the samples with 5 wt % Ag indicate at least factor of 2 improvement in the critical current.

Electronic properties and resonant states in AlMn(−Si) alloys

Detailed experimental studies of quasi-crystalline Al 100−xMn x(Si) alloys have shown that the magnitude of electrical resistivity as well as the excess specific heat term δγ are proportional to the percentage of manganese in the samples, as is the case in well-known very dilute AlMn alloys. We argue that the excess specific heat term and the high resistivity (about 150–200 μω cm for the quasi-crystalline phase) can be accounted for within the extended Friedel-Anderson s-d model, in which the dominant scattering is due to the hybridization of d electrons with the sp conduction band. Therefore, in our physical picture, the high resistivity in AlMn quasi-crystals is mainly due to the contributions from two effects: the existence of narrow resonant states of manganese at the Fermi level and the existence of correlation lengths of the order of 100–300 Å which cause the incoherence of transport electrons.

Correlations between Nondestructive and Destructive Tests on High-Voltage Coil Insulations for Rotating Miachines

The correlations between results of nondestructive and destructive tests on high-voltage coil insulations for rotating machines were investigated and the following findings were obtained. Breakdown voltage on application of a commercial line voltage (50 Hz) is correlated to the voltage at which a partial discharge bridges the insulation layer. Breakdown voltage on application of a direct voltage is correlated with the discharge magnitude, dielectric constant and dielectric loss tangent corresponding to void discharge in the insulation layer. Breakdown under an impulse waveform voltage is in some respects similar to that under commercial frequency but, because of the short duration of voltage application, it is correlated with the magnitude of electrical resistance, and this correlation is related to the ease with which the bridge phenomenon of discharge in the insulation layer propagates. Thus, the correlation between breakdown voltage and electrical characteristics in nondestructive tests varies with the voltage waveform involved. In tapewound laminated structures, as in micaceous insulatopms, breakdown occurs along the lap of tape, so that characteristic phenomena of the breakdown process for various voltage waveforms combining mutually correlated characteristics, are observed.