Precision Electrical Resistance Research Articles

Analysis of the Long-Term Corrosion Behavior of X80 Pipeline Steel in Acidic Red Soil Using Electrical Resistance Test Technique

The long-term corrosion rate of X80 steel in an acidic red soil was monitored in situ by using a precise electrical resistance (ER) test system. The corrosion characteristics of X80 steel were examined via SEM, EDS, and XRD. The results indicated that the corrosion rate determined from ER test was very similar to that obtained from the mass loss test. The ER test technique made it possible to predict the long-term corrosion rate of steel in soil in situ. The corrosion rate of X80 steel in acidic red soil was about 0.0902 mm/a at 38 weeks, but the corrosion rate was dropped to 0.0226 mm/a after 5 years. The final corrosion product layer was composed mainly of FeOOH,γ-Fe2O3, and FeCO3.

The Novel Phase Diagram of YbPd

Precise electrical resistivity and ac calorimetry measurements under pressures have revealed the (P, T) phase diagram of a mixed-valent compound YbPd. The diagram is rather complicated, reflecting the valence and magnetic instability. In addition to the reported phase transitions at TN = 1.9 K and TMH = 0.5 K, the lower temperature transition at TML = 0.3 K has been confirmed thermodynamically. TN decreases monotonically up to 1.7 GPa and disappears discontinuously at Pc ~1.9 GPa, accompanying the drastic enhancement of the effective mass and the residual resistivity, although the ordered phase below TML still remains. At Pc, the both of magnetic and valence fluctuations seems to develop.

Method for the formation of cylindrical current and its application to evaluate electrical resistivity

A cylindrical current method is developed to obtain a stable and precise electrical resistivity of a specimen with or without a coating film. The electrical resistivity of a standard silicon wafer doped with boron at a concentration can be measured using the proposed method if the experimental results of electrical voltage varying with the distance from the center line of the cylindrical current are available. A comparison of the electrical resistivity obtained using the present method and the theoretical reference value indicates that the proposed method produces reliable and precise measurements. Using four test samples, the experimental results of electrical resistivity measured by the present method are shown to be reproducible and more precise than those measured by the four-terminal sensing method and the van der Pauw method. The electrical voltage and current obtained at various distances from the center line of the cylindrical current are almost independent of the distance and the direction of measurements. The effect of specimen's crystallinity appears to be the governing factor of electrical resistivity. Electrical resistivity decreases with increasing crystallinity generally.

Crossover Phase Diagram in Heavy Fermion Compound YbCo2Zn20

We studied the electronic state and metamagnetic behavior in the heavy fermion compound YbCo 2 Zn 20 by measuring the specific heat, ac-susceptibility, and electrical resistivity under magnetic fields. The magnetic specific heat in the form of C mag / T increases steeply with decreasing temperature below 10 K and becomes constant with an extremely large value 8 J/(K 2 ·mol) below about 0.2 K, indicating a Fermi-liquid nature in this temperature range. The magnetic entropy increases rapidly below 10 K and reaches R ln 8 around 60 K, suggesting a small crystalline-electric-field (CEF) splitting energy. From the precise electrical resistivity measurements, together with the C ( H )/ T and χ ac ( T ) measurements, it was found that there are two crossover lines at low temperatures in the H – T phase diagram for H ∥<100>. The Fermi-liquid state evolves at lower temperatures than these crossover lines.

(P, T) Phase Diagram of Clathrate Superconductor Ba24Ge100

Precise electrical resistivity and ac calorimetry measurements under pressures have revealed (P, T) phase diagram of superconducting clathrate Ba24Ge100. Following conventional superconducting theory, the pressure dependence of the density of state at Fermi energy, N(EF), estimated by the electronic specific heat C/T has been discussed with the Tc(P). Up to P= 2.1 GPa, where Tc(P) starts to saturate, C/T increases with Tc in agreement with the theory. On further compression, C/T is strongly suppressed while Tc slightly decreases. Across Pc ~ 2.9 GPa, where structural deforming transitions at Ts1(s2) are suppressed, pressure variation of C/T becomes smaller. In addition to the enhancement of the N(EF), other changes in crystal and/or electrical structure may play important roles to pressure dependence of Tc in Ba24Ge100.

Critical Phenomena in Magnetic Nanowires

In this paper we report the first experimental study of critical phenomena in case of magnetic nanowires of nickel near the ferromagnetic-paramagnetic transition from the electrical transport properties. Nickel nanowire arrays, prepared by potentiostatic electrodeposition of nickel inside pores of nanoporous anodic alumina template were well characterized by X-ray Diffraction, Transmission electron microscopy and Energy dispersive Spectroscopy. Precise electrical resistance measurement of the nanowire arrays of wire diameter 20 nm have been done in the temperature range between 300 K to 700 K. We see a drop in the Curie temperature as observed from the resistivity anomaly. We analyzed the resistance data near the critical region and extracted the critical exponent alpha directly from the resistance. We observed a decrease in the critical part of the resistivity including a decrease in the magnitude of the critical exponent alpha and severe modification in the correction to scaling.

The kinetics of structural relaxation of bulk and ribbon glassy Pd 40Cu 30N 10P 20 monitored by resistance and density measurements

Density and in situ high precision electrical resistance measurements on bulk and ribbon glassy Pd 40Cu 30Ni 10P 20 in the initial state, after cold rolling and quenching from the supercooled liquid state are performed. Three relaxation stages resulting in different signs of the electrical resistance relaxation are determined. It is shown that the resistance change upon structural relaxation is predominantly controlled by the resistivity relaxation while the volume change has a minor effect on the resistance. Cold rolling has a complex impact on the electrical relaxation similar to the effect of plastic deformation on the dislocation anelasticity in crystals. Quenching of fully relaxed samples from the supercooled liquid state recovers structural relaxation and the amount of the resistance relaxation can be several times bigger than that in the initial state. It is concluded that relaxation of the electrical resistance as dependent on different conditions (bulk/ribbon samples, thermocycling, rolling and the parameters of quenching from the supercooled liquid state) is rather complex but it is unlikely that the degree of the relaxation is governed by the amount of the free volume. This conclusion agrees with the established fact of equal density of initial glassy and crystallized bulk samples and earlier findings of nearly equal shear viscosity of bulk and ribbon samples different by four orders of magnitude in the production quenching rate.

Influence of gd addition on the structure and properties of Au-Ni and Au−Ni−Cr alloys

The influence of Gd additions on the microstructure and properties of Au-Ni and Au-Ni-Cr alloys are reported. The alloys remain single phase solid solution at Gd contents of −0.1wt%, but at contents τ 0.1%, two phases structures are formed, consisting of (Au) and a low melting point intermetallic compound containing Gd. Trace additions of Gd refine the grain size, increase strength and the recrystallization temperature, but without detriment to the good electric conductivity of these alloys. The wear life of potentiometer windings made of gold alloys containing Gd are at least one order of magnitude higher than those made in the Gd-free gold alloys. The design of gold alloys for precise electrical contact and resistance materials by conventional and microalloying is discussed.

WEAK-LOCALIZATION EFFECT IN SINGLE CRYSTAL TaN(001) FILMS

We here report the manifestation of weak localization effects in the electrical resistivity of TaN (001) films grown on MgO (001) substrates by a pulsed laser deposition technique. These films were characterized by X-ray diffraction and Rutherford backscattering. High precision electrical resistivity measurements were performed on these films in the temperature range 12–300 K. A careful analysis of data showed these films to lie in the weakly localized regime with negative temperature coefficient of resistivity throughout the whole temperature range of study. A crossover from 2D localization at lower temperatures to 3D localization at higher temperatures was observed.

Low temperature electrical transport in La 1− xNd xNiO 3− δ

We have investigated low temperature electrical transport in La 1− x Nd x NiO 3− δ perovskite oxide samples. Samples were prepared by a sol–gel method and were characterized by X-ray diffraction and chemical methods. High precision electrical resistivity, magnetoresistance (MR) and electron tunneling conductance measurements were performed. Crystal structure investigations showed a phase transition from rhombohedral to orthorhombic phase at x=0.4. In the orthorhombic phase Ni–O–Ni bond angle was found to depend very sensitively on the value of x; as the value of x increases Ni–O–Ni bond angle decreases resulting in the tilting of NiO 6 octahedra. A Correlation between the Ni–O–Ni bond angle and electrical transport has been observed. The analysis of the electrical resistivity data showed the presence of disorder driven quantum correction effects, namely e–e interactions and weak localization, in the system. A dip in the tunneling density of states and negative MR also suggest the presence of e–e interaction and weak localization effects in the system.

Single Crystal TaN Thin Films on TiN/Si Heterostructure

AbstractWe have successfully grown epitaxial cubic (B1-NaCl structure) tantalum nitride films on Si (100) and (111) substrate using a pulsed laser deposition technique. A thin layer of titanium nitride was used as a buffer medium. We characterized these films using X-ray diffraction, high resolution transmission electron microscopy and scanning transmission electron microscopy (Zcontrast). X-ray diffraction and high-resolution transmission electron microscopy confirmed the single crystalline nature of these films with cubic-on-cubic epitaxy. The epitaxial relations follow TaN(100)//TiN(100)//Si(100) on Si(100) and TaN(111)//TiN(111)//Si(111) on Si(111). We observed sharp interfaces of TaN/TiN and TiN/Si without any indication of interfacial reaction. Rutherford backscattering experiments showed these films to be slightly nitrogen deficient (TaN0.95). High precision electrical resistivity measurements showed excellent metallic nature of these films. We also tried to deposit TaN directly on silicon, the films were found to be polycrystalline. In our method, TiN plays a key role in facilitating the epitaxial growth of TaN. This method exploits the concept of lattice matching epitaxy between TaN and TiN and domain matching epitaxy between TiN and Si. We studied the diffusion barrier properties of these films by growing a thin layer of copper on the top and subsequently annealing the films at 500°C and 600°C in vacuum. Cu diffusion layer was about 2nm after 600°C annealing for 30min. This work explores a promising way to grow high quality TaN diffusion barrier on silicon for copper interconnection.

Unusual electrical resistivity anomalies of thulium thin films at low temperatures

High precision electrical resistance measurements were performed in the temperature range from 4.2 K up to room temperature on a pure thulium bulk sample with a high residual resistivity ratio, RRR=146, and on thulium thin films in the thickness interval from 25 to 115 nm. The observed size-effect of the electrical resistivity is in accordance with theory and it is without resistivity vs. thickness anomalies. The typical “hump-backed” anomaly in the resistivity vs. temperature dependence was observed for the Tm bulk sample near the Néel temperature. In contrast, unexpected resistivity vs. temperature anomalies were observed for thulium thin films in the low temperature region below ∼60 K and near ∼170 K. A crystal structure study using X-ray diffraction revealed that these thin films were single phase with the Tm hcp crystal structure and with preferential orientation of crystallites.

Structural and transport properties of high energy ion irradiated YBCO

The effects of 100 MeV Oxygen and 200MeV Silver ions on the structural and transport properties of YBCO thin films are reported. Both normal state and superconducting properties were studied on Laser ablated and high pressure oxygen sputtered films. Precise electrical resistance and critical current measurements near T c were made and the data obtained were analysed in the light of existing models of para-coherence near T c and the other aspects of radiation damage arising from microstructural studies such as atomic force microscopy (AFM). There was evidence of sputtering by high energy ions from AFM measurement.

Crystallization characterisics in the Fe [sbnd]Si [sbnd]B glassy ribbon system

The kinetics of crystallization of Fe 80Si xB 20 − x (with x = 2, 4, 6, 8, 10) and Fe 75Si 15B 10 glassy ribbons was examined using differential scanning calorimetry and high precision electrical resistivity measurements. The main crystallization parameters are presented. The corresponding structure of the materials was observed using transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The mechanism of crystallization is described in terms of the local ordering (cluster) model.

A fully automated precise electrical resistance measurement system

A fully automated precise electrical resistance measurement system for more than one sample has been constructed. Conventional four-probe measurements with van der Pauw and Montgomery configurations are possible with this system. Resistance measurements in the range of a few μΩ to a few GΩ are possible for six samples at a time from room temperature down to liquid-helium or liquid-nitrogen temperatures with a temperature control accuracy of better than 10 mK. The design features of the system with special reference to the low-noise switching methods of currents and voltages are described in detail. Precision of the results thus obtained using this system are highlighted for a few superconducting and semiconducting samples.

Highly accurate electrical resistance measurement apparatus for high temperature

In order to investigate the details of an atomic configuration in metals and alloys, a precise electrical resistance measurement apparatus at high temperatures was constructed. Accuracy of temperature control is found to be 0.01 °C at around 300 °C, and the accuracy of the electrical resistivity measurement is 0.01 nΩ cm for an aluminum sample which has an electrical resistivity of 6×103 nΩ cm at around 300 °C. Using the apparatus, thermal generation of a vacancy at 320 °C in a highly perfect aluminum crystal was detected.

Asymptotic critical behaviour of quenched random-exchange Heisenberg ferromagnets

Asymptotic and leading 'correction-to-scaling' critical exponents and critical amplitudes for zero-field specific heat, spontaneous magnetization and initial susceptibility have been accurately determined for quenched random-exchange Heisenberg ferromagnets through an elaborate analysis of highly precise electrical resistivity, bulk magnetization and AC susceptibility data taken on amorphous FexNi80-x(B,Si)20 (x=10, 13, 16 and 20) alloys in the critical region. The values of critical exponents and universal critical amplitude ratios so obtained do not depend on composition and conform very well with the corresponding estimates given by the renormalization-group calculations for quenched random site- and bond-diluted Heisenberg ferromagnets. The amplitude ratios ac1+/ac1- and ac1+/achi 1+, which are characteristic of ferromagnets with quenched random disorder and for which no theoretical estimates are presently available, seem to possess universal character for they too are composition-independent. The experimental results are consistent with the concept of scaling in that the exponent equalities alpha += alpha -, beta + gamma = beta delta and alpha + gamma =2(1- beta ) are obeyed to a high degree of accuracy and the magnetization data satisfy the scaling equation of state characteristic of second-order phase transition. The effect of the isotropic long-range dipolar interactions on the asymptotic critical behaviour is mainly felt through the enhanced value of the A+/A$ratio. Only a small fraction of moments actually participates in the ferromagnetic(FM)-paramagnetic(PM) phase transition for the alloys with Fe concentration x not very far from, but above, the critical concentration xc and this fraction reduces further at a rapid rate as xc is approached along the FM-PM phase transition line in the magnetic phase diagram.

Hydrogen in niobium under pressure

By means of electrotransport and high precision electrical resistance measurements we studied the influence of hydrostatic pressure (up to 2.2 GPa) on the diffusion coefficient and some related properties of hydrogen in niobium. The hydrogen-to-niobium ratio was varied from 0.002 to 0.05 and the temperature from −80 to 160 °C. At atmospheric pressure the results for the diffusion coefficient are in accordance with the results from the Gorsky effect and quasi-elastic neutron scattering experiments. Even within the high precision of our measurements no change in the diffusion coefficient could be observed under hydrostatic pressure. This is in contradiction to theoretical predictions. Electrotransport measurements also provide information on the effective charge Z∗ of the screened proton in niobium. Below 20 °C, Z∗ increases rapidly with decreasing temperature. High pressure does not change Z∗ and its temperature dependence. This must be due to a negligible influence of high pressure on the electronic structure of hydrogen in niobium. The specific electrical resistivity change due to dissolved hydrogen is not altered as a function of pressure. From this it is concluded that the lattice distortions due to hydrogen in niobium are not changed by high pressure.

Hydrogen in niobium under pressure

By means of electrotransport and high precision electrical resistance measurements we studied the influence of hydrostatic pressure (up to 2.2 GPa) on the diffusion coefficient and some related properties of hydrogen in niobium. The hydrogen-to-niobium ratio was varied from 0.002 to 0.05 and the temperature from −80 to 160 °C. At atmospheric pressure the results for the diffusion coefficient are in accordance with the results from the Gorsky effect and quasi-elastic neutron scattering experiments. Even within the high precision of our measurements no change in the diffusion coefficient could be observed under hydrostatic pressure. This is in contradiction to theoretical predictions. Electrotransport measurements also provide information on the effective charge Z ∗ of the screened proton in niobium. Below 20 °C, Z ∗ increases rapidly with decreasing temperature. High pressure does not change Z ∗ and its temperature dependence. This must be due to a negligible influence of high pressure on the electronic structure of hydrogen in niobium. The specific electrical resistivity change due to dissolved hydrogen is not altered as a function of pressure. From this it is concluded that the lattice distortions due to hydrogen in niobium are not changed by high pressure.

The Interaction between Vacancy and 3d-Transition Elements in Dilute Gold Alloys

In order to investigate the interaction between a vacancy and 3d transition elements (Fe, Co and Ni) in Au, the annealing behaviour of quenched-in vacancies in dilute Au alloys is examined by means of precise electrical resistivity and positron lifetime measurements. Several sub-stages appeared in the recovery curve of both resistivity and positron lifetime, and they were explained by taking the motion of vacancy-solute pairs into account. From the analysis of the effective migration energies obtained in the final annealing stage where the dissociation of VS pairs were expected to take place, the binding energies of VS were obtained to be 0.35, 0.33 and 0.20 eV for Fe, Co and Ni solute, respectively. These values are fairly large, contrary to the theoretical calculations. Based on these results, the origin of the strong binding was pursued and the new concept of `covalency effect' was proposed.