Intermediate phases in superconducting niobium-tin alloys

Wyman, L. L.; Cuthill, J. R.; Moore, George A.; Park, J. J.; Yakowitz, H.

doi:10.6028/jres.066a.037

Cited by 21 publications

(3 citation statements)

References 6 publications

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“…Single-phase, f3-tungsten structure deposits on wire and ribbon substrates had compositions ranging between 76.2 and 81.5 atomic percent niobium because of changing conditions in the deposition process. This composition range is in a close agreement with the phase diagram proposed by Wyman et al (1962), who have shown that in the niobium-tin system above 863C only one compound exists with very nearly the same composition range as that given above.…”

Section: E Physical Properties and Chemical Analysissupporting

confidence: 80%

Superconductivity of Metals and Alloys

Gennes¹

2018

1,478

896

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of RCA Laboratories were project engineer and project supervisor, respectively. Accession poll i 3TIS GRA&IDTIC ABSTRACTMeasurements were made of the Kapitza resistance in tin and indium and its change at the superconducting transition. For comparison with theory, measurements were also made on the insulator, sapphire. An attempt to detect an electric field dependence of the Kapitza resistance in platinum had negative results.A new method for the preparation of 6-tungsten compound superconductors, such as Nb Sn, was developed. Both the properties of the deposited material and the extension of this method to such possible a6-tungsten compounds as niobium germanide, niobium silicide, vanadium-gallium, vanadium silicide and niobium-gallium are described.The transition temperature of niobium stannide is shown to depend not only on the stoichiometry, but also on the state of order of the lattice. Resistivity of Nb3Sn is given as a function of temperature from 4.2 0 K to 370 ¶K. Tunneling measurements on deposited Nb 3 Sn indicate the existence of a bandgap (2ev). Preliminary results are compatible with the relation: 2 fo = 1.8 T,.Penetration depth measurements were made on deposited Nb3 Sn. The temperature dependence is similar to that obtained for other superconductors, but the value of the penetration depth at T = OK (2,880 A) is almost an order of magnitude larger than that observed for soft superconductors. This value and the predictions of the BCS (Bardeen, Cooper, and Schrieffer, 1957) theory in the local limit are compared. A comparison is also made with recent theories of hard superconductors.Quenching currents were measured on deposited Nb 3 Sn. Preliminary results indicate a zero field quenching current close to that predicted by the Silsbee hypothesis assuming a thermodynamic critical field H. 0 5,000 gauss. For transverse fields the quenching current drops rapidly, whereas for longitudinal fields the quenching current rises. Comparison of these results are made with recent theories of hard superconductors.Thermal conductivity measurements were made on Nb 3 Sn. Preliminary results indicate qualitative agreement with the predictions of the microscopic theory of superconductivity.In the Appendix, results are given from a study on the thermal effect of resistive current contacts on the quenching current of niobium stannide.This Technical Documentary Report has been reviewed and is approved.

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Section: E Physical Properties and Chemical Analysissupporting

confidence: 80%

Superconductivity of Metals and Alloys

Gennes¹

2018

1,478

896

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“…The specimens presently under investigation by quantitative m etallography are part of a series of diffusion specimens and reacted powder mLxtures which have been under investigation by a number of methods in an effort to establish the phase diagram of the Nb-Sn system and to determine the most effective method of preparing the NbaSn phase [8].…”

Section: Niobium-tin Alloy Systemmentioning

confidence: 99%

“…The colors produced on different metallographic constituents vary somewhat with the degree of anodization, and can be deliberately varied to aid in distinguishing phase areas. On the basis of microspot spectrochemical analyses of characteristic areas, the constituents in the microstructures have been tentatively identified [8] as shown in table 2.…”

Section: Niobium-tin Alloy Systemmentioning

confidence: 99%

Quantitative metallography with a digital computer: Application to a Nb-Sn superconducting wire

Moore¹,

Wyman²

1963

J. RES. NATL. BUR. STAN. SECT. A.

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Accurate quanti tative data pertin c nt to the structurc of solid m a terials at the micro size level, w hi ch a re diffi cul t or prohibi tive to ob ta in by trad itiona l manual measure ments are ~ow o btain e~ direc~l y b.v a dig;ital co mpu ter wh ich uses a photomicrograph a s the infor: m atlO n lI1pu t. The histo ry of picture in terpretation experime nts at the Natio na l Bureau of Standards. is. reviewed: The f undamental computer ope ration s are illustrated, together wit h a descnp tlOn of 24 unage processing r outin es no\\" funct ional at a practical level. " . A mi.crograph of a spec ime n of Nb-Sn s up erco ndu ctor wire is exha ustively a na lyzed. IIns SpeCI}lle ll IS found to conta ll1 approxImate ly 70 percent Nb3Sn, nea rly a ll of \\' hi ch i'i mutually lI1terco nn ected . It is a lso fo und that in t hi s Rpecime n the mean free path in the N b3Sn s uperconducting phase i~ onl y 26.5 microns. This sma ll value res ults from th e s pongy str ueture of t h e materi a l and numerous in terruptions caused by voids a nd by part icles of four other solie! phases . The comparative importance of the severa l t ypes of i nte rrup tio ns is m easured. I t is determ ined t hat small vo ids a re the most impor ta nt s ingle ca use of th e short m ean free path , a nd deduced t hat t hese \'oids a ppea r to ha ve formed main ly from the reaction dUI'ing heat treatment.

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Die Darstellung von Phasengebieten in Zustandsdiagrammen einiger supraleitender Systeme mit Hilfe der Elektronenstrahl‐Mikroanalyse

Ronami¹

1972

Cryst Res and Technol

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Die Ergebnisse zahlreicher Untersuchungen beweisen, daß sich die Methode der Diffusionsschichten bei Anwendung der Röntgenspektral‐Mikroanalyse zur Konstruktion von Phasenfeldern der Zustandsdiagramme verwenden läßt. Die Übereinstimmung der Resultate, die durch die Analyse von Diffusionsschichten erhalten wurden, mit Ergebnissen anderer physikalisch‐chemischer Analysenmethoden (im besonderen für die Systeme Cu‐Zn, Ag‐Zn und Cu‐Ag‐Zn) ist gut. Die Anwendung der Röntgenspektral‐Mikroanalyse zur Untersuchung der Zusammensetzung der Diffusionszonen erlaubt es, die Konzentration mit einer Genauigkeit bis zu 1 Gew.‐% zu bestimmen. Die Methode der Diffusionsschichten ist unentbehrlich für die Aufstellung von Zustandsdiagrammen der Systeme, die aus Elementen mit sehr unterschiedlichen Schmelztemperaturen oder aus schwerschmelzenden Elementen bestehen, bei denen die Anwendung anderer physikalisch‐chemischer Methoden wegen der sehr komplizierten Herstellung der Legierungen außerordentlich erschwert ist. Vorteile der Diffusionsmethode bei Anwendung der Elektronenstrahl‐Mikroanalyse im Vergleich mit den klassischen Methoden zur Ermittlung von Phasenfeldern in Zustandsdiagrammen sind: geringe Anzahl der zu untersuchenden Objekte, direkte Bestimmung der Konzentration der Phasen, relativ geringer Zeitaufwand zur Aufzeichnung und Auswertung der Konzentrationskurven. Die in der Arbeit angeführten Daten zur Kinetik der Wechselwirkung zwischen schwer‐ und leichtschmelzenden Metallen stimmen mit den Ergebnissen vieler Diffusionsuntersuchungen bei einer großen Anzahl binärer Systeme überein.

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Intermediate phases in superconducting niobium-tin alloys

Cited by 21 publications

References 6 publications

Superconductivity of Metals and Alloys

Superconductivity of Metals and Alloys

Quantitative metallography with a digital computer: Application to a Nb-Sn superconducting wire

Die Darstellung von Phasengebieten in Zustandsdiagrammen einiger supraleitender Systeme mit Hilfe der Elektronenstrahl‐Mikroanalyse

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