LOW TEMPERATURE RESISTIVITY OF THE TRANSITION ELEMENTS: COBALT, TUNGSTEN, AND RHENIUM

1957 ◽  
Vol 35 (5) ◽  
pp. 656-665 ◽  
Author(s):  
G. K. White ◽  
S. B. Woods
Keyword(s):  
Electrical Resistivity ◽  
Low Temperature ◽  
Thermal Resistance ◽  
High Purity ◽  
Thermal Resistivity ◽  
Superconducting Transition ◽  
Transition Elements ◽  
Experimental Values ◽  
Thermal Vibrations ◽  
Temperature Resistivity

Experimental values are reported for the electrical resistivity from 1.5° to 300° K. and for the thermal resistivity from 2° to 120° K. of high purity cobalt, tungsten, and rhenium. The temperature variation of the components of the electrical and of the thermal resistance due to scattering by thermal vibrations is deduced and the possible evidence for the importance of s–d transitions is discussed briefly. The temperature of the superconducting transition in samples of rhenium is found to be close to 1.70° K., the value reported by Hulm (1954).

LOW TEMPERATURE RESISTIVITY OF TRANSITION ELEMENTS: VANADIUM, NIOBIUM, AND HAFNIUM

1957 ◽  
Vol 35 (8) ◽  
pp. 892-900 ◽  
Author(s):  
G. K. White ◽  
S. B. Woods
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Electrical Resistivity ◽  
Electrical Resistance ◽  
Thermal Resistivity ◽  
Superconducting Transition ◽  
Transition Elements ◽  
Pure Niobium ◽  
Temperature Resistivity ◽  
The Ideal

Measurements of the thermal conductivity from 2° to 90 ° K. and electrical conductivity from 2° to 300 ° K. are reported for vanadium, niobium, and hafnium. Although the vanadium and hafnium are not as pure as we might wish, measurements on these metals and on niobium allow a tabulation of the "ideal" electrical resistivity clue to thermal scattering for these elements from 300 ° K. down to about 20 ° K. Ice-point values of the "ideal" electrical resistivity are 18.3 μΩ-cm. for vanadium, 13.5 μΩ-cm. for niobium, and 29.4 μΩ-cm. for hafnium. Values for the "ideal" thermal resistivity of vanadium and niobium are deduced from the experimental results although for vanadium and more particularly for hafnium, higher purity specimens are required before a very reliable study of "ideal" thermal resistivity can be made. For the highly ductile pure niobium, the superconducting transition temperature, as determined from electrical resistance, appears to be close to 9.2 ° K.

LOW TEMPERATURE RESISTIVITY OF THE TRANSITION ELEMENTS: RUTHENIUM AND OSMIUM

1958 ◽  
Vol 36 (7) ◽  
pp. 875-883 ◽  
Author(s):  
G. K. White ◽  
S. B. Woods
Keyword(s):  
Electrical Resistance ◽  
Room Temperature ◽  
Inert Gas ◽  
Thermal Resistivity ◽  
Transition Elements ◽  
Arc Melting ◽  
Regular Shape ◽  
Gas Atmosphere ◽  
Experimental Values ◽  
Temperature Resistivity

Experimental values are reported for the electrical resistivity of ruthenium and osmium from 2 to 300 °K and for the thermal resistivity from 2 to 140° K. The samples were produced by arc-melting pressed pellets of metallic powder in an inert gas atmosphere. Two osmium samples and one ruthenium sample showed a satisfactorily low residual electrical resistance. By grinding these rods to a regular shape, absolute values of resistivity were obtained and the impurity and thermal components of resistivity derived; at room temperature (295 °K) we deduce that for ideally pure Os, [Formula: see text] and for ideally pure ruthenium [Formula: see text]. The temperature dependence of the resistivity was markedly different for another ruthenium sample but it seems likely that this was not representative of pure h.c.p. ruthenium.

Electrical and thermal resistivity of the transition elements at low temperatures

1959 ◽  
Vol 251 (995) ◽  
pp. 273-302 ◽  
Keyword(s):  
Electrical Resistivity ◽  
Transport Equation ◽  
Low Temperatures ◽  
Group Iv ◽  
Standard Theory ◽  
Thermal Resistivity ◽  
Transition Elements ◽  
Thermal Vibrations ◽  
The Ideal

The results of measurements on 20 transition elements are reported giving values for the thermal resistivity, W , from 2 to about 140 °K and for electrical resistivity, p , from 2 to about 300 °K. Values of the ‘ideal’ resistivities, W i and p i { (due to scattering of the electrons by thermal vibrations), are deduced from these and tabulated for various temperatures. Comparisons are made with values for Cu, Ag, Au and Na and with the predictions of the ‘standard’ theory, i.e. solutions of the transport equation developed by Bloch, Grüneisen, Wilson, etc. Excepting Mn, p i follows a Bloch—Grüneisen function tolerably down to op5, although slight anomalies are shown by V, Cr, Fe, Co and Ni; at low temperatures behaviour is varied but below 10 °K in Mn, Fe, Co, Ni, Pd, Pt and perhaps in W and Nb, p i appears to vary nearly as T<super>2</super>. The parameter, piM 6 & (at 273 °K) has rather similar values for different members of each group, e.g. for Ti, Zr and Hf of group IV A. The ideal thermal resistivity, Wif can generally be approximated by the relation, WiIW ao = 2(Tld)2J 5(dlT), although for many elements, W i falls more rapidly than T 2 below010. Measurements on the relatively poor conductors, e.g. Ti, Zr and Hf, suggest the presence of an appreciable lattice conductivity, which affects the confidence with which values can be deduced for W i in these elements.

scholarly journals Computational Intelligence Approach for Estimating Superconducting Transition Temperature of Disordered MgB2Superconductors Using Room Temperature Resistivity

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Taoreed O. Owolabi ◽  
Kabiru O. Akande ◽  
Sunday O. Olatunji
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Room Temperature ◽  
Optimization Technique ◽  
Support Vector ◽  
Measuring Instruments ◽  
Room Temperature Resistivity ◽  
Superconducting Transition ◽  
Experimental Values ◽  
Temperature Resistivity

Doping and fabrication conditions bring about disorder in MgB2superconductor and further influence its room temperature resistivity as well as its superconducting transition temperature (TC). Existence of a model that directly estimatesTCof any doped MgB2superconductor from the room temperature resistivity would have immense significance since room temperature resistivity is easily measured using conventional resistivity measuring instrument and the experimental measurement ofTCwastes valuable resources and is confined to low temperature regime. This work develops a model, superconducting transition temperature estimator (STTE), that directly estimatesTCof disordered MgB2superconductors using room temperature resistivity as input to the model. STTE was developed through training and testing support vector regression (SVR) with ten experimental values of room temperature resistivity and their correspondingTCusing the best performance parameters obtained through test-set cross validation optimization technique. The developed STTE was used to estimateTCof different disordered MgB2superconductors and the obtained results show excellent agreement with the reported experimental data. STTE can therefore be incorporated into resistivity measuring instruments for quick and direct estimation ofTCof disordered MgB2superconductors with high degree of accuracy.

THERMAL AND ELECTRICAL CONDUCTIVITY OF RHODIUM, IRIDIUM, AND PLATINUM

1957 ◽  
Vol 35 (3) ◽  
pp. 248-257 ◽  
Author(s):  
G. K. White ◽  
S. B. Woods
Keyword(s):  
Electrical Conductivity ◽  
Electrical Resistivity ◽  
High Purity ◽  
Low Temperatures ◽  
Rapid Rate ◽  
Transition Elements ◽  
Electron Collisions ◽  
Electrical Conductivities ◽  
Electrical Resistivities ◽  
The Ideal

Measurements are reported of the thermal and electrical conductivities of the transition elements Rh, Ir, Pt in a state of high purity; the rapid rate of decrease of the "ideal" thermal and electrical resistivities with temperature, particularly in Rh and Ir, suggests that s–d transitions are not a dominant resistive mechanism at low temperatures in these metals, in contrast to palladium, iron, and nickel, which were studied previously. The electrical resistivity of platinum is in general agreement with the earlier results of de Haas and de Boer (1934); the quadratic dependence on temperature observed below about 10° K. suggests that electron–electron collisions may well be an important factor in this metal.

Thermoelectric Properties of the Pseudogap Fe2VAl System

2004 ◽  
Vol 449-452 ◽  
pp. 909-912 ◽  
Author(s):  
Yoichi Nishino
Keyword(s):  
Electrical Resistivity ◽  
Electronic Structure ◽  
Low Temperature ◽  
Seebeck Coefficient ◽  
Room Temperature ◽  
Sharp Decrease ◽  
Large Power ◽  
Large Enhancement ◽  
Level Shifts ◽  
Temperature Resistivity

While the Heusler-type Fe2VAl compound exhibits a semiconductor-like behavior in electrical resistivity, doping of quaternary elements causes a sharp decrease in the low-temperature resistivity ρ and a large enhancement in the Seebeck coefficient S. Substantial enhancement in S can be explained on the basis of the electronic structure where the Fermi level shifts slightly from the center of a pseudogap either up- or downward depending on doping. In particular, a slight substitution of Si for Al leads to a large power factor (P = S2/ρ) of 5.5×10-3W/m K2at around room temperature.

Physical Property Evaluation for High Purity Niobium and Tantalum Rare Metals

2007 ◽  
Vol 26-28 ◽  
pp. 1059-1062 ◽  
Author(s):  
Il Ho Kim ◽  
Jung Il Lee ◽  
G.S. Choi ◽  
J.S. Kim
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Low Temperature ◽  
Temperature Dependence ◽  
High Purity ◽  
Phonon Scattering ◽  
Physical Property ◽  
Rare Metals ◽  
Metallic Behavior ◽  
Property Evaluation

Thermal, electrical and mechanical properties of high purity niobium and tantalum refractory rare metals were investigated to evaluate the physical purity. Higher purity niobium and tantalum metals showed lower hardness due to smaller solution hardening effect. Temperature dependence of electrical resistivity showed a typical metallic behavior. Remarkable decrease in electrical resistivity was observed for a high purity specimen at low temperature. However, thermal conductivity increased for a high purity specimen, and abrupt increase in thermal conductivity was observed at very low temperature, indicating typical temperature dependence of thermal conductivity for high purity metals. It can be known that reduction of electron-phonon scattering leads to increase in thermal conductivity of high purity niobium and tantalum metals at low temperature.

Thermal and electrical conductivities of the alkali metals at low temperatures

1956 ◽  
Vol 235 (1202) ◽  
pp. 358-374 ◽  
Keyword(s):  
Alkali Metals ◽  
Current Theory ◽  
Thermal Resistivity ◽  
Free Electrons ◽  
Sodium Potassium ◽  
Electrical Conductivities ◽  
Semi Empirical ◽  
Thermal Vibrations ◽  
Temperature Resistivity ◽  
Good Agreement

Measurements of the thermal and electrical conductivities of very pure lithium, sodium, potassium, rubidium and caesium have been made down to temperatures as low as 2°K. The respective resistivities, W and ρ , may be written as the sum of an impurity resistance ( W 0 , ρ 0 ) and a so-called ‘ideal’ component ( W i , ρ i ) due to scattering by the thermal vibrations of the lattice. The terms in the thermal resistivity may be represented by W 0 = A / T and W 1 = B T n f o r T ≤ θ / 10 , where n ≃ 2 and A = ( ρ 0 /2⋅45) x 10 8 cm deg. 2 W -1 . Current theory predicts thatt he quantity C ≡ Bθ 2 / W ∞ N ⅔ should be constant, where N is the number of free electrons per atom and W is the measured high-temperature resistivity. Taking N = 1, the present experiments yield C ≃ 18 ± 4. The electrical resistance may be written ρ = ρ 0 + β T m f o r T < θ / 10 with m ≃ 5 except for sodium, where, below 8°K , m is found to increase to 6. The theoretical relationships which exist between the low-temperature ‘ideal’ resistivities and those at higher temperatures are discussed in conjunction with the measured values. It is concluded that with the existing theories, no common adjustment of θ can give satisfactory agreement of theory with experiment. A new simple semi-empirical expression is put forward for W i which provides rather good agreement with experiment.

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