US3887364A - Superconducting materials - Google Patents

Superconducting materials Download PDF

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US3887364A
US3887364A US311148A US31114872A US3887364A US 3887364 A US3887364 A US 3887364A US 311148 A US311148 A US 311148A US 31114872 A US31114872 A US 31114872A US 3887364 A US3887364 A US 3887364A
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percent
atomic percent
atomic
critical temperature
superconducting
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Ushio Kawabe
Mitsuhiro Kudo
Shigeo Fukase
Masato Ishibashi
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Hitachi Ltd
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Hitachi Ltd
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/80—Constructional details
    • H10N60/85—Superconducting active materials
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
    • C22C27/02—Alloys based on vanadium, niobium, or tantalum
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S420/00—Alloys or metallic compositions
    • Y10S420/901—Superconductive
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/80—Material per se process of making same
    • Y10S505/801—Composition
    • Y10S505/805—Alloy or metallic
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/80—Material per se process of making same
    • Y10S505/801—Composition
    • Y10S505/805—Alloy or metallic
    • Y10S505/806—Niobium base, Nb

Definitions

  • o 3 ,r o.
  • This invention relates to useful'and novel superconducting materialsand. more particularly, to improved intermetallic compound superconducting materials having high critical temperature and a ,B-W type crystalline structure generally represented by a formula 1-1/ y)l ⁇ ' la r)- BRIEF DESCRIPTION OF THE PRIOR ART characters are thought to be very suitable as the material for superconducting magnet coils and superconducting transmission cables.
  • the critical temperature T of B-W type binary compounds is only as high as l8K in case of Nb Sn and NbaAl and no superconductivity at higher temperatures has heretofore been obtained in binary compounds.
  • An object of the invention is to provide a novel superconducting material, which has high critical temperature and can be readily manufactured as practical material, and with which it is possible to alleviate the cooling conditions in its practical use.
  • part of Al in the Nb Al type structure is replaced with another element M, and also part of Nb is, if necessary, replaced with Ta.
  • the value of K is set within a range from about 2.8 to about 4.0.
  • the element substituted for Al and the quantity of partial substitution may be about 3.2 atomic percent or less of Pb or Ce, about 3.8 atomic percent or less of Bi or Te, about 4.4 atomic percent or less of TI, about 6.4 atomic percent or less of Cu, about 5.8 atomic percent or less of Sb, about 4.2 atomic percent or less of Y, about 2.7 atomic percent or less of Pr or Eu, about 2.1 atomic percent or less of Ca, or about 7.2 atomic percent or less of Zn.
  • FIG. 1 is a graph showing relations among critical temperature, averaged phonon frequency, pseudocoulomb potential and electron-phonon coupling constant for some superconducting materials.
  • FIG. 2 shows relations between calculated value and observed value of Debys temperature for some B-W type compounds.
  • FIG. 3 is a graph showing relations between electronphonon coupling constant and coefficient of electronic specific heat for some B-W type compounds.
  • FIG. 4 is a graph showing relations between coefficient of electronic specific heat of some B-W type compounds and' number of electrons per atom in the crystal.
  • FIG. 5 shows a model of C-D binary phase diagram with a showing of Debys temperature and coefficient of electronic specific heat for Nb c D, compounds plotted against x.
  • FIG. 6 shows four main types of binary diagram having an eutectic or eutectoid point.
  • FIG. 7 is a graph showing relations between critical temperature and concentration of element M for Nb (Al, M) alloys according to the invention.
  • FIG. 8 is a graph showing relations between critical temperature and concentration of Cu for (Nb, Ta) (Al, Cu) alloys according to the invention, with various concentrations of Ta.
  • FIG. 9 is a graph showing relations among critical temperature, K and x for Nb (Al, ,Zn alloys according to the invention.
  • the B-W type intermetallic compound Nb Al dealt with in the present invention is featured by a composite crystalline structure consisting of a body-centered cubic lattice formed by Al atoms, and Nb atoms lying in three perpendicular planes of the lattice.
  • T critical temperature
  • Nb-Nb atom chain in the B-W crystalline structure forms a very narrow d-band in the vicinity of the Fermi-level, thus increasing the Fermi-level d-electron state density and the superconducting critical temperature.
  • the critical temperature T. of a superconducting material is given as
  • the averaged phonon frequency w is generally determined by the phonon spectrum, and in case of the B-W type structure it is approximately 1.3 times the Debys temperature
  • the value of 6, may be calculated from Lindemanns formula of melting point that holds well for simple metallic substances and alloys.
  • a. is the B-W type crystal lattice constant
  • T is the melting temperature
  • M is the mean atomic weight.
  • FIG. 2 shows the correlation between observed Debys temperature and calculated Debys temperature for some known B-W type compounds. It will be seen that equation 2 holds fairly well although there is a tendency of forming clusters in dependence upon whether 3-d or 4-d band is occupied by the electrons of the element occupying the A site of intermetallic compounds represented by a general formula A C. Thus, it will be understood that to increase the value of 0 the compound should be converted into a multi-element material of a reduced lattice constant, an increased melting point and an increased molecular weight.
  • the third parameter A can be defined by the McMillans theory as mentioned earlier. It may also be obtained semiexperimentally from known data as shown in FIG. 3, in which the electron-phonon coupling constant and coefficient of electronic specific heat 'y are correlated for known B-W type compounds. As is shown, the relation between 'y/) ⁇ and 'y is represented by a straight line, whose x or y-intercept differs in dependence upon the d-band that is occupied by the electrons of the element occupying the A site of the compound A C but whose slope is the same in either case. In this way, there holds a linear relation between 7 and A for a group of compounds having the same d-band structure.
  • the value of A may be determined if the magnitude of y is determined.
  • the parameter y may also be obtained from data as shown in FIG. 4, in which y of various B-W type compounds A C is plotted against the number Z of electrons per atom in the B-W type crystal, that is, the ratio between total electron number e and atom number a.
  • the value of y greatly varies in dependence upon which of 3-d, 4-d and 5-d bands is occupied by the electrons of the high melting transition element occupying the A site.
  • the value of 7 continuously changes with Z depending upon the kind of element occupying the C site.
  • the ,B-W type multi-element superconducting compounds obtained by incorporating two different foreign metals are generally represented as'
  • the critical temperature of this type of materaial is greatly influenced not only by the kind of the substitution elements B and D but also by the composition ratios (.r, y and K) and various heat treatment conditions.
  • the critical temperature T will be the highest with a value of K in the proximity of 3.0. With this value of K, however, the range of x with which it is possible to expect satisfactory results is very narrow. With greater values of K the critical temperature T may be increased for a broader range of X, but the highest value of T, would be reduced. If the value of K exceeds 4.0, the super conducting character will be deteriorated.
  • the concentration x of the element D should be selected to be in the proximity of the composition corresponding to the eutetic point of a binary eutectic alloy of C and D.
  • the upper half of FIG. 5 is a model of C-D binary phase diagram, and the lower half of FIG. 5 shows the Debys temperature and coefficient of electronic specific heat for Nb C D, compounds plotted against x corresponding with the upper half. It will be seen from this FIGURE that the Debys temperature of the Nb (C,D) compound is the highest and the coefficient of electronic specific heat is large for the composition corresponding to the eutectic point of the elements occupying the C site.
  • the superconducting character of Nb C compound may be improved particularly at the critical temperature thereof.
  • FIG. 6 shows four main types of phase diagrams of C and D, corresponding to A C and A -,D combinations, the D component occupying the C site in case of havng Nb as the element A and Al as the element C. Namely, there are Pb type, Cu type, Sb type with some varieties and eutectoid type.
  • the critical temperature T is higher compared to NbgAI.
  • the desired concentration x of the element D corresponding to the proximity of the eutectic point of the C-D alloy tends to be slightly influenced by the concentration y of the element Ta, but the resultant deviation may be empirically determined.
  • EXAMPLE 1 This example deals with B-W type ternary superconducting materials represented by a formula Nb Al M where M is a member of a group consisting of Pb, Bi, Tl, Cu, Sb, Te, Y, Ce, Pr, Eu, Ca and Zn.
  • Samples of materials with compositions containing the above elements were obtained through a combination of plasma arc melting or sintering and levitation melting. Materials in the form of masses and with purities of at least'99.99 percent are weighed to prepare predetermined compositions, and the resultant compositions were subjected to plasma arc melting in an argon atmosphere under pressure of around 1 atm. to
  • buttons-like masses were inverted several times for sufficient alloying.
  • the button-like masses were subjected to levitation melting in an argon atmosphere, and the resultant fused materials were cast into water-cooled copper molds to producerod-like samples.
  • powdery materials were used, and predetermined compositions were sufficiently mixed and press molded with a pressure of l ton/cm.
  • the resultant moldings were temporarily sintered in an argon atmosphere under a pressure of about 1.5 atm. and at a temperature of not higher than l,OO0C. to produce samples containing low-grade intermetallic compounds poor in Nb, which were then subjected to levitation melting as mentioned above to produce rod-like samples.
  • the critical temperature T.- of the samples obtained in the above manner was measured by the usual four resistance probe technique. More particularly, the critical temperature T is set to the temperature when the resistance recovered and just reaches one half of the difference of resistance between the superconducting state and normal state, wherein the sample is 30 mm long carries a constant current of several amperes per square centimeter between its ends.
  • FIG. 7 shows relations between critical temperature T and atomic concentration or atomic percent x of the element M for various Nb3Al M ternary alloys having been subjected to a heat treatment at a temperature of 700C. for hours.
  • M is Pb, Ce, Bi, Te, Pr, Eu or Ca
  • the critical temperature T is the highest when about 1.25 atomic percent of Al is replaced with the third element M, that is, when x is set to about 0.05.
  • the eutectic point of these Al-M systems lies between 1 and 5 atomic percent of the concentration of the element M, which substantially corresponds to the value of x of the element M when the critical temperature T is at its peak.
  • the critical temperature T is relatively high when up to about 5.0 atomic percent of Al is replaced with the element M, that is, for values ofx up to about 0.2, and the concentration x of the element M corresponding to the peak of the critical temperature T, substantially coincides with the corresponding concentration at the eutectic point of the Al-M system except for the case where M is Sb.
  • the highest critical temperature obtained was 19.3K with Nb (Al,Zn).
  • Table 1 lists the concentration range of the element M necessary to obtain T higher than about 18K, the concentration range of the element M necessary to obtain T higher than about 18.5l( and the most desirable concentration range of the element M to increase T
  • the presence of about 0.05 atomic percent of M except for Sb leads to appreciable effects, while the presence of about 2 atomic percent of Sb leads to appreciable effects.
  • EXAMPLE 2 This example deals with quarternary superconducting materials obtained by replacing part of Nb with Ta in the samples in the first example.
  • FIG. 8 shows relations between critical temperature T and concentration for Cu for B-W type intermetallic compounds according to the invention having composi- ⁇ ions of t).98 0.02)3 l-r r)a 0.95 0.0s)a i- ,Cu,) and Nb (Al .,Cu,).
  • the samples in this embodiment were prepared as in Example 1.
  • the critical temperature of materials obtained by replacing part of Nb with Ta in the Nb (Al,M) system is higher, although slightly, compared to that of samples without incorporating Ta.
  • the range of concentration of Ta to obtain the above effects is less than about 4.0 atomic percent.
  • EXAMPLE 3 deals with ternary superconducting materials obtained by changing the concentration of Nb in the samples in the first example.
  • FIG. 9 shows relations between critical temperature T. and concentration of Zn for alloys having B-W type crystalline structure and composition of Nb (Al .,Zn,) when K is 2.8, 3.0 and 4.0 respectively.
  • the method of preparation of samples and method of measurement of the critical temperature are similar to the previous first and second examples.
  • alloys represented as Nb (Al .,M,) show high critical temperatures when K is within a range of 2.8 s K S 4.0. If the value of K is smaller than 2.8, no appreciable improvement of the critical temperature can be obtained. Also, where x representing the concentration of the element M substituted for Al is less than about 0.15, the critical temperature is highest with a value of K in the proximity of 3.0. For greater values of x, better results may be obtained with values of K greater than 3.0. However, with values of K greater than 4.0 the characteristics of the material becomes instable, and satisfactory results cannot be expected.
  • the concentration of Nb corresponding to the above range of K is about 74 to 80 atomic percent. As has been mentioned in the second embodiment, less than about 4 percent of Nb may be replaced with Ta, and in such case the lower limit of the concentration of Nb is about 70 atomic percent.
  • the superconducting materials according to the invention said materials having B-W type crystalline structure and, multielement compounds which have novel composition of Nb-Al-M or Nb-Ta-Al-M (where M is a member selected from the group consisting of Pb, Bi, Tl, Cu, Sb, Te, Y, Ce, Pr, Eu, Ca and Zn) have higher critical temperature T, l9.3K at the highest) compared to that of the Nb Al materials and have characteristics sufficient for use as practical material.
  • M is a member selected from the group consisting of Pb, Bi, Tl, Cu, Sb, Te, Y, Ce, Pr, Eu, Ca and Zn
  • a superconducting material having high critical temperature said material being an alloy represented by the formula: Nb-Al-M, wherein M is an element selected from the group consisting of 0.053.8 atomic percent of Te, 0.05-2.4 atomic percent of Y. 3.2-4.2 atomic percent of Y. 0.05-3.2 atomic percent of Ce. 0.05-2.7 atomic percent of Pr, 0.05-2.7 atomic percent of Eu, 0.05-2.1 atomic percent of Ca and 0.05-7.2 atomic percent of Zn, wherein the amount of Nb is in a range of 74-80 atomic percent and the balance of said alloy is Al and very minor amounts of unavoidable impurities.
  • M is an element selected from the group consisting of 0.053.8 atomic percent of Te, 0.05-2.4 atomic percent of Y. 3.2-4.2 atomic percent of Y. 0.05-3.2 atomic percent of Ce. 0.05-2.7 atomic percent of Pr, 0.05-2.7 atomic percent of Eu, 0.05-2.1 atomic percent of Ca and 0.05-7.2 atomic
  • a superconducting material having high critical temperature greater than 18.5K said material being an alloy represented by the formula Nb-Al-M, where M is an element selected from the group consisting of 0.2-3.2 at percent of Te, 0.6-1.9 at percent of Y,

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4010047A (en) * 1974-05-16 1977-03-01 Siemens Aktiengesellschaft Method for stabilizing a superconductor
US4402768A (en) * 1980-05-24 1983-09-06 Kernforschungszentrum Karlsruhe Gmbh Method for producing superconductive wires of multifilaments which are encased in copper or a copper alloy and contain niobium and aluminum
US4409297A (en) * 1981-05-14 1983-10-11 The United States Of America As Represented By The Secretary Of The Navy Composite superconductors
US4983358A (en) * 1989-09-13 1991-01-08 Sverdrup Technology, Inc. Niobium-aluminum base alloys having improved, high temperature oxidation resistance
US5522945A (en) * 1994-07-01 1996-06-04 General Electric Company Method for forming triniobium tin superconductor with bismuth

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5313194U (enrdf_load_stackoverflow) * 1976-07-16 1978-02-03

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3244490A (en) * 1963-09-10 1966-04-05 Nat Res Corp Superconductor
US3290186A (en) * 1963-05-20 1966-12-06 Rca Corp Superconducting materials and method of making them
US3544316A (en) * 1968-03-14 1970-12-01 Rca Corp Superconductors

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3290186A (en) * 1963-05-20 1966-12-06 Rca Corp Superconducting materials and method of making them
US3244490A (en) * 1963-09-10 1966-04-05 Nat Res Corp Superconductor
US3544316A (en) * 1968-03-14 1970-12-01 Rca Corp Superconductors

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4010047A (en) * 1974-05-16 1977-03-01 Siemens Aktiengesellschaft Method for stabilizing a superconductor
US4402768A (en) * 1980-05-24 1983-09-06 Kernforschungszentrum Karlsruhe Gmbh Method for producing superconductive wires of multifilaments which are encased in copper or a copper alloy and contain niobium and aluminum
US4409297A (en) * 1981-05-14 1983-10-11 The United States Of America As Represented By The Secretary Of The Navy Composite superconductors
US4983358A (en) * 1989-09-13 1991-01-08 Sverdrup Technology, Inc. Niobium-aluminum base alloys having improved, high temperature oxidation resistance
US5522945A (en) * 1994-07-01 1996-06-04 General Electric Company Method for forming triniobium tin superconductor with bismuth

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JPS522798B2 (enrdf_load_stackoverflow) 1977-01-24

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