... Accession Number : ADD101939. Title : SUPERCONDUCTING A-15 COMPOUNDS: A REVIEW,. Corporate Author : Personal ...
DTIC Science & Technology
The A-15 (A sub 3 B) compounds comprise an important class of superconducting compounds. In order to gain a clearer understanding of the parameters influencing the superconductivity in these materials, several A-15 compounds have been prepared and the eff...
National Technical Information Service (NTIS)
... Descriptors : *Superconductors, *Radiofrequency, Niobium compounds, Tin, Transition temperature, Surface properties, Resistance, Chemical ...
Recently there has been a resurgence of interest in the effect of the martensitic phase transition which occurs in many A15 compounds on superconductivity and on elastic and anelastic behavior. Since in many practical applications, A15 compounds are subje...
... can be used to study the electronic configuration which is responsible for superconductivity in Laves-phase crystals like A-15 compounds and beta ...
the bulk residual resistivities reported for other A-15 compounds. The ... and A -15 compounds exhibit exceptionally high critical supercurrent den- sities. ...
NASA Website
Search Criteria: Search Field: All > Results : All > Search Term: (A-15 Compounds) [x]. Sort results by: NASA Center | Date Added to NTRS | Publication Year ...
The early history of the bronze process is recapitulated and modifications to the process which have since followed are described. The metallurgical principles, which are involved in the process, are described including the kinetics of the compound growth...
A model has been developed for the recovery of T/sub c/ in radiation-damaged A-15 compounds. This model has been applied to isothermal annealing data at 550 exp 0 C on a sample of Nb sub 3 Ge, and to isochronal annealing (200 exp 0 C to 900 exp 0 C) data ...
The lattice parameters and the x-ray intensity data of two new A-15 compounds (Ti4Tl and Zr4Tl) are reported. In connection with searching for possible superconducting transitions in these compounds, four others (V3Pd, Ti3Au, Ti3Hg and Zr3Hg) were reinves...
Large, reversible changes in the superconducting transition temperature T sub c of the Nb-based A-15 compounds Nb3Al, Nb3Sn, Nb3Ga, Nb3(Al, Ge), and Nb3Ge are observed when irradiated with high-energy(E greater than 1 MeV) neutrons at 60 C. The transition...
The purpose of this work was to investigate the optical properties of several high T/sub c/ compounds in the form of sputtered films. The measurements are used toward this end: optical absorptance (using a calorimetric technique near 4.2K), which yields (...
From transmission electron microscopy and heat capacity measurements radiation induced damage in A-15 compounds was found to be inhomogeneous, consisting of small disordered regions in an ordered matrix. Some consequences of this result are discussed.
Energy Citations Database
From transmission electron microscopy and heat capacity measurements, radiation induced damage in A-15 compounds was found to be inhomogeneous, consisting of small disordered regions in an ordered matrix. Some consequences of this result are discussed. (E...
Recently there has been a resurgence of interest in the effect of the martensitic phase transition which occurs in many A15 compounds on superconductivity and on elastic and anelastic behavior. Since in many practical applications, A15 compounds are subject to considerable ...
Formulas are given both for the volume dependence of the transition temperature Tc of transition metals and for the Tc of well-ordered A15 compounds. Both formulas yield results in reasonable agreement with experiment. Measurements are proposed to facilit...
The extremely low surface resistance exhibited by superconductors makes possible some interesting and important applications in microwave electronics. Chief among these are (1) the use of high-field superconducting cavities as high-power, coherent, pulsed...
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A15 superconductivity compounds of general formula A/sub 2/B are manufactured by forming an alloy of B in a carrier, contacting the alloy with A and heat treating so that a solid state reaction occurs between A and B.
The work reported has focused on completing experiments on heavy dose implantations into substrates with an A-15 structure and on initiating experiments on melt spinning for forming new A-15 compounds and amorphous ribbons. The effect of ion implantation ...
In this paper various data for the depression of T/sub c/ and N(O) are presented for a wide class of A15 materials. The question of disorder and the limits on T/sub c/ in these materials are discussed.
DOE Information Bridge
A survey of theoretical research on acoustic plasmons is given and prospects for the observation of these elusive modes are examined. Possible acoustic plasmon contributions to the transition temperatures of the superconducting A-15 compounds are considered. Directions for future experiments and theory are suggested.
NASA Astrophysics Data System (ADS)
The critical currents of superconducting A15 Nb--Ge and Nb--Ge--Si compounds prepared by CVD have been measured in applied fields up to 18 T. Current densities greater than 10/sup 5/ A cm/sup -2/ were obtained at 18 T. These results are discussed with regard to the microstructure of the films which were examined by transmission ...
Elastic strains alter (usually, but not always, adversely) the critical temperatures, magnetic fields, and current densities of superconducting A15 compounds; non-hydrostatic strain states are particularly effective in this regard. This paper is a review of the experimental evidence, obtained by a variety of techniques, concerning the ...
A self-consistent pseudopotential technique is used to study various surface systems. Calculated results are compared with photoemission experiments. Electronic states associated with the presence of steps on surfaces are investigated by considering a model structure of the Si(111) surface containing steps. A method to the problems of hydrogen and chlorine chemisorption on the Si(111) surface was ...
The theoretical treatment of the relation between the critical angle of planar channeling and the characteristics of crystal lattice defects is carried out. The predictions are made about some typical forms of the critical angle dependence on the mean-square static displacement produced by defects, and then these predictions are detailed for the cases of homogeneous disordering, spherical clusters ...
Three binary A-15 compounds (Zr4Sn, Ta3Sb, Ta4Au) were reinvestigated and all three found to be superconducting below 1 degree K. Ternary compounds V3(Al,X), (X = As, Ge, Au) were also investigated in the composition range where the A-15 structure is stab...
Partial Contents: Ternary Compounds; Granular Superconductors; Superconductivity in (SN)x and its Halogen Derivative (SNBr0.4)x; Studies of cuCl at Elevated Pressures; Superconducting Properties of Hydride Systems; Thin Film Superconducting Materials Research; Synthesis of Superconducting Nb3Si using High Pressures; Synthesis of Unstable ...
Electron microscopic observations of neutron irradiated Nb/sub 3/Sn revealed the presence of highly disordered regions of size approximately 35A in a much less disordered matrix. This observation is shown to provide a means of explaining quantitatively many superconducting properties of irradiated A-15 compounds. In particular T/sub c/ ...
The structural instability in high temperature A-15 superconductors is examined from a phenomenological, Landau theoretic point of view, based on the picture of an electronically driven lattice instability. emphasis is given to lattice properties--in particular, the extended softening of phonons in k-pace and phonon linewidth. Implications of the extended ...
The structural instability in high temperature A-15 superconductors is examined from a phenomenological, Landau theoretic point of view, based on the picture of an electronically driven lattice instability. emphasis is given to lattice properties-in particular, the extended softening of phonons in k-pace and phonon linewidth. Implications of the extended ...
The universal depression of the superconducting transition temperature Tc in disordered A-15 compounds is examined. Existing energy-band calculations are used to calculate the density of electron states, which is possibly enhanced by disorder in some cases such as Nb3Ge. The dramatic drop in Tc in Nb3Ge at a critical value of the ...
The intermetallic compound Nb3 Ge with the Al5-type crystal structure ... demonstrated for several material systems as illustrated by the ... otherwise, its Tc is 6 K. Some A15 materials, especially those pseudo-binary ... been used recently to form the compound Nb3 Sn from its elemental ..... Cu-tube. ...
Calculations of the electron-phonon interaction, lambda, and T/sub c/ are presented for ten different A15 compounds, V/sub 3/X and Nb/sub 3/X, X = Al, Ga, Si, Ge, and Sn. The calculated temperature-dependent magnetic susceptibility of Nb/sub 3/Sn is also shown to be in good agreement with experiment. We argue that the low-temperature ...
The universal depression of the superconducting transition temperature T/sub c/ in disordered A-15 compounds is examined. It is found that their anomalous behavior can be explained by a simple model for the density of states, which is enhanced by disorder in some cases. The dramatic drop in T/sub c/ in constant density-of-states ...
A-15 compounds are extremely brittle and difficult to process for practical applications. A novel processing technique was developed to greatly improve the mechanical and superconducting properties of A-15 alloys. The new processing technique can be described as follows: (1) to select compounds that can form the ...
We introduce a three-dimensional k-->.p--> model for the electronic structure of A-15 compounds based upon a six-dimensional irreducible representation R(4) of the space group Oh3-Pn3m. By locating the Fermi level near the maximum in the density of states, the temperature-dependent free energy accounts quantitatively for anomalous normal-state physical properties of ...
The early history of the bronze process is recapitulated and modifications to the process which have since followed are described. The metallurgical principles, which are involved in the process, are described including the kinetics of the compound growth, the effects of additives on the growth, etc. The superconducting properties of these compounds are ...
