The role of high-frequency phonons in the resistivity of simple monovalent metals at liquid helium temperatures

We derive an expression for the low-temperature electrical resistivity in simple monovalent metals caused by electron-impurity and electron-phonon scattering. Since the recent measurements of the electrical resistivity of van Kempen et al. give direct evidence for the existence of phonon drag we take phonon drag into account. Our expression is exact in the limit of strong electron-impurity scattering. For the model of an acoustically isotropic metal we obtain a simple analytical formula which reproduces the experimental data on potassium fairly well, with both fitparameters, the sound velocity and the pseudopotential, being close to the values expected from other data.     

On the electrical resistivity in intermediate valence compounds arising from electron-phonon scattering

The static and frequency dependent electrical resistivity in intermediate valence compounds arising from electron-phonon scattering is calculated by applying the memory function method to the periodic Anderson model. It is shown that in the static limit the resistivity may be considerably enhanced due to a finite fraction of 4f electrons being present at the Fermi level. This partial filling of the 4f shell is also responsible for the fact that the real part of the conductivity, which by Drude's formula is a Lorentzian of width 1/τ₀, is drastically reduced to an effective width 1/τ.     

良导体热导率不同测量法的比较

维德曼-弗兰兹定律指出金属的热导率和电导率的比值是常数,本文先测量了一定温度下的材料的电阻率,再由电阻率计算出材料的热导率,并与利用热波法得到的热导率进行比较,其结果相近.     

射频溅射Pd薄膜的电阻率研究

本文研究了溅射Pd薄膜的电阻率与膜厚关系和不同溅射功率下Pd薄膜电阻率,结果表明,电阻率与膜厚的关系与现有的薄膜电阻率尺寸效应的理论基本相符,存在的差异主要是由溅射对衬底温度影响而引起的,并显示玻璃衬底上生长膜也有择优取向,溅射功率的变化对电阻率有一定的影响,进一步讨论溅射过程中衬底温度变化的问题,得出膜电阻率随衬底温度变化的定量关系式。 关键词：     

The electrical resistivity of mixed valence materials due to nonmagnetic impurities

We have studied the influence of nonmagnetic impurities on the electrical resistivity of a mixed valent host. The model we consider is the periodic Anderson model where we change the energy parameters at the sites occupied by the randomly distributed impurities. The propagator of the pure system has been obtained by a decoupling scheme [1]. We use the CPA to perform the impurity average for the one-particle Green's function and Kubo's formula to calculate the electrical conductivity. Numerical analysis shows that the resistivity decreases monotonously with increasing temperature. This is in contrast to experimental results [2, 3] and possible reasons for the incorrect low-temperature behaviour are discussed.Dedicated to B. Mühlschlegel on the occasion of his 60th birthdayAddress after October 1985: Imperial College, Department of Physics, Prince Consort Road, London SW7 2BZ, UK     

DC electrical resistivity for CoxNi5/3−xSb1/3Fe1O4 ferrites

The DC electrical resistivity (p) was studied for Co substituted SbNi ferrites as a function of temperature and composition. The experimental results showed that DC resistivity, Curie temperature and activation energies for electrical conduction increase as Co-ion substitution decreases. The DC electrical conductivity increases as temperature increases. The real part of dielectric constant (e') was found to be inversely proportional to the root mean square value of the electrical resistivity.     

纯金属电阻率的统计模型

本文提出了纯金属电阻率与声子浓度及声子平均动量的平方成正比的统计模型，由此简化模型，给出了纯金属电阻率的一个解析表达式，理论与实验规律相符，即在高温时，电阻率与温度Ｔ成正比，低温时与Ｔ＾５成正比。     

金属薄膜厚度小于电子自由程对其光反射率的影响

提出了金属薄膜厚度对薄膜中自由电子的平均自由程影响的物理模型,并给出了薄膜中自由电子的平均自由程的修正公式.理论研究表明:当膜厚小于自由电子的平均自由程时,薄膜中电子平均自由程随膜厚的减小而减小|当膜厚大于或等于自由电子的平均自由程时,薄膜中电子的平均自由程与块状材料一样.利用薄膜中电子平均自由程的计算公式,修正了薄膜导电率的基本理论表达式,再利用金属薄膜的反射率与薄膜导电率的关系,得出金属薄膜厚度对其光反射率的影响.计算机模拟表明:当薄膜厚度小于电子自由程时,金属薄膜反射率随薄膜厚度变化而呈非线性关系.     

Cr80-xFe20Mnx(x=10,15,20)合金的低温电阻率和热导率

报道了Cr80-xFe20Mnx(x=10,15,20)合金在10—300K的电阻率和热导率．结果表明样品的电输运性质和热输运性质均与样品的磁状态有关．在SDW反铁磁转变附近,电阻率出现极小．对Neel温度以下电阻率-温度曲线拟合结果表明：取温度相关的能隙函数2△∝√（TN-T）可以很好地描述SDW反铁磁能隙随温度降低而打开的过程．合金在反铁磁转变温度以下表现出与无序样品或者玻璃态样品类似的热导率温度关系,这可能是源于合金中磁性团簇的散射．     

Theory of the residual electrical resistivity of binary actinide alloys

A system of self-consistent equations has been proposed for the coherent potential approximation of the multiband conductivity model for the case of conduction electron scattering from chaotic electric fields of ions of disordered binary alloy components at zero temperature. It has been qualitatively demonstrated that the deviation of the concentration dependence of the residual electrical resistivity of actinide alloys with multiband conductivity from the Nordheim rule is caused by the explicit dependence of the electrical resistivity of the alloy on the magnitude and sign of the real part of the Green’s function at the Fermi level. The derived system of equations for the multiband coherent potential approximation has been used to calculate the concentration dependence of the density of states and the residual electrical resistivity of the alloys of neptunium and plutonium. The results of the calculations have been compared with the available experimental data.     

Thermal conductivity of indium at high pressures and temperatures under shock compression

The results of investigations of the electrical and thermal conductivity of indium in the pressure range up to 27 GPa and at temperatures up to 1000 K are presented. In this pressure range, the electrical resistance of indium samples is measured under multishock compression. The equation of state constructed for indium is used to calculate the evolution of the thermodynamic parameters of indium in shock wave experiments; then, the dependences of the electrical resistivity and thermal conductivity coefficient on the volume and temperature are determined. It is demonstrated that, in the pressure and temperature ranges under investigation, the thermal conductivity coefficient of indium does not depend on temperature and its threefold increase is caused only by the change in the volume under compression.     

Thermal conductivity of high-porosity heavily doped biomorphic silicon carbide prepared from sapele wood biocarbon

The electrical resistivity and thermal conductivity of high-porosity (～52 vol %, channel-type pores) bio-SiC samples prepared from sapele wood biocarbon templates have been measured in the temperature range 5–300 K. An analysis has been made of the obtained results in comparison with the data for bio-SiC samples based on beech and eucalyptus, as well as for polycrystalline β-SiC. The conclusion has been drawn that the electrical resistivity and thermal conductivity of bio-SiC samples based on natural wood are typical of heavily doped polycrystalline β-SiC.     

Influence of oxide scale thickness on electrical conductivity of coated AISI 430 steel for use as interconnect in solid oxide fuel cells

The use of conductive coating on interconnect ferritic stainless steel can reduce electrical resistivity. In this study, an AISI 430 ferritic stainless steel interconnect was coated with a manganese base pack mixture by pack cementation. The effect of oxide scale thickness on electrical conductivity was evaluated by applying isothermal oxidation at 750?°C. This effect was also investigated at different temperatures (400?C900?°C). The formation of manganese spinels during annealing improved the oxidation resistance and electrical conductivity. Results showed that the increase in isothermal oxidation time and temperature increased the oxide thickness, and this resulted in the relatively low values of electrical conductivity. Manganese spinels enhanced the electrical conductivity and oxidation resistance of coated substrates as compared to uncoated substrates.     

Effect of copper addition on some properties of rapidly solidified lead-free Sn–-10 wt% Zn alloys

This study aimed at investigating the effect of adding copper (Cu) on some properties of the lead-free alloys which rapidly solidified from melt. X-ray analysis, hardness, elastic modulus, electrical conductivity and resistivity were studied. The results indicated that the alloy hardness and elastic modulus improved by increasing the copper (Cu) content and decreasing the zinc (Zn) content. The electrical conductivity ranged from 0.250 to 0.847?×?10⁷ ohm^?1 m^?1 for the alloy under study. The electrical resistivity increases linearly with temperature until the melting point is reached. The residual resistivity results from disturbances in the lattice rather than caused by thermal vibration and the most drastic increases in the residual resistivity are caused by foreign atoms in solid solution with matrix metal. The electrical resistivity values ranged from 11.8 to 40?×?10^?8 ohm m, when the copper content changed from 0.0 to 2.0 wt% and zinc changed from 8.0 to 10.0 wt%.     

A theory of electrical conductivity in metallic glasses

In this paper is presented a phenomenological theory of electrical conductivity in metallic glasses based on the method of so-called modified relaxation time (till now applied to semi-conductive glasses only). The essential difference consists of a consistent use of Fermi-Dirac statistics because of the degeneracy of electron gas. The results that this theory yields obviously elucidate the existence of both positive and negative values of the resistivity coefficient in metallic glasses and lead to the conclusion that the minimum in the temperature dependence of electrical conductivity may not be necessarily related to the so-called Kondo effect. This is a simple consequence of the interaction between positive (metallic) and negative (semiconducting) contributions to the electrical conductivity which appears in the metallic glasses due to disorder.     

Thermal conductivity and electrical resistivity of bulk indium and indium embedded in 7-nm channels of porous borosilicate glass

A “porous glass + indium” nanocomposite has been prepared. The thermal conductivity κ(T) and electrical resistivity ρ(T) of the nanocomposite have been measured in the temperature range 5–300 K, and their fractions accounted for by nanoindium embedded in 7-nm channels of the porous glass have been determined. For comparison, κ and ρ of the bulk polycrystalline indium sample have been measured in the same temperature range. The electronic and phonon components of the thermal conductivity have been calculated for the nanoindium and bulk indium. It has been demonstrated that, as the result of the emergence of boundary electron and phonon scattering in the nanoindium, the electrical resistivity of this material becomes larger, and the phonon thermal conductivity, smaller than those of the bulk indium.     

C-axis thermoelectric transport in low stage SbCl5 graphite intercalation compounds

c-axis thermal conductivity, electrical resistivity and thermopower measurements performed on stages-2, 3 and 4 SbCl₅-graphite intercalation compounds in the temperature range 3 < T < 300 K are reported. Contrary to the electrical resistivity and thermopower data, the temperature variation of the thermal conductivity is qualitatively different from that previously observed on other intercalation compounds.     

General electrical transport properties of polycrystalline multi-layered metallic thin films

We have derived, following the recent theoretical calculation of the electrical conductivity of multi-layered metallic thin films, a general solution of the electrical conductivity for those films with grain structures, since those structures give important contributions to the electrical transport properties of polycrystalline thin film. The temperature coefficients of resistivity have also been obtained.     

Dc electrical conductivity of Ge2S3Agx glasses at high hydrostatic pressure

The paper deals with the influence of hydrostatic pressure on d.c. electrical conductivity in Ge₂S₃Ag _x glasses forx10%. The initial material exhibits high resistivity and the presence of Ag impurity yields strong increase in electrical conductivity. The experimental results suggest that there is a non-linear decrease of electrical resistivity at pressure ranging from 0·1 to 10³ MPa. The pressure coefficient of resistivity is a function ofx. All measurements were performed on bulk samples using graphite contacts. The experimental results are interpreted by means of ionic conductivity.     

Electrophysical properties of carbon nanocomposites based on nanodiamonds irradiated with fast neutrons

The electrophysical properties of nanoporous carbon composites consisting of a nanometer-sized pyrolytic carbon matrix and nanodiamonds have been analyzed. It has been shown that the power-law dependence of the electrical resistivity on the thickness of the pyrolytic carbon layer D on a log-log scale has an inflection for D = 1 Å. It has been found that the temperature dependence of the electrical resistivity of the nanocomposite is described by an exponential function with an exponent of 1/4 for both unirradiated samples and samples irradiated with fast neutrons. This is characteristic of variable-range hopping conductivity in the case of strong localization in systems with semiconductor conductivity in the presence of a local disorder. With an increase in the neutron fluence, the electrical resistivity of the studied material changes very significantly (by several hundred percent) and nonmonotonically. This result is associated with the transformation of the structure of the graphite-like matrix and with possible graphite-diamond phase transitions.