Superconductivity and phase stability of Nb3Ge

Sweedler, A.R.; Cox, D. E.; Moehlecke, S.; Jones, Richard H.; Newkirk, L. R.; Valencia, F.A.

doi:10.1007/bf00657172

Cited by 44 publications

(9 citation statements)

References 20 publications

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“…This was undertaken because of the quantitative experimental results which link the Tc degradation in irradiated Nb3Ge with the neutron fluence. From a paper by Sweedler et al 6 the effects of high-energy neutron irradiation of Nb3Ge can be found in Fig. 7.…”

Section: Filamentary Superconductivitymentioning

confidence: 99%

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Superconductivity in NbGe2 and isostructural C-40 compounds

Knoedler

Douglass

1979

J Low Temp Phys

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The superconductivity of NbGe2 and isostructural C-40 compounds has been studied in a quantitative manner. The high transition temperatures (To = 16 K) exhibited by sputtered films of NbGe2 are shown to be an intrinsic property of the compound and are attributed to the degree of order produced during the formation process. The roles of excess germanium and thermal effects are also discussed for NbGe2. One of the major conclusions established in this study is that a new crystal structure type, namely the hexagonal C-40 system, is superconducting. Four binary compounds are shown to exhibit superconductivity; they are NbGe2 (To = 16K), NbSi2 (To = 2.9K), TaSi2 (Tc = 4.4 K), and TaGe2 (T~ = 2.7K). Even though superconductivity has been demonstrated on these compounds, the mechanism responsible for the superconductivity has not been established.

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Section: Filamentary Superconductivitymentioning

confidence: 99%

“…Materials which exhibit the relation between ordering and enhanced transition temperatures are Nb3Ge, V3Au, VaGa, Mo-Tc, and others. A recent investigation by Sweedler et al 6 studied the effects of ordering on the Tc of Nb3Ge. This was accomplished in part by annealing.…”

Section: Introductionmentioning

confidence: 99%

Superconductivity in NbGe2 and isostructural C-40 compounds

Knoedler

Douglass

1979

J Low Temp Phys

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“…According to Gavaler et aI.1"3 and Sweedler et al, 19 long-term annealing of Nb-Ge films (consisting of Nb3Ge, NbsGe3, etc.) above 700~ produces no increase but only a decrease in Tc in the films, and the decrease in Tc is accompanied by an increase in lattice constant of the NbaGe phase and an increase in the amount of the tetragonal NbsGe3 phase.…”

Section: Influence Of Gas Flow Rates On Superconducting Transition Tementioning

confidence: 99%

“…above 700~ produces no increase but only a decrease in Tc in the films, and the decrease in Tc is accompanied by an increase in lattice constant of the NbaGe phase and an increase in the amount of the tetragonal NbsGe3 phase. It has been concluded from these phenomena by Sweedler et al 19 that the stoichiometric Nb3Ge phase is metastable and upon annealing transforms to a stable, Nb-rich Nb3Ge phase accompanied by precipitation of the tetragonal NbsGe3 phase. In order to determine the effect of annealing at lower temperatures on Tc in Nb3Ge films, in our experiment some of the deposited films consisting of a predominant Nb3Ge phase and a small amount of NbsGe3 phase and having both Tc.on above 22 K and Tc, midpoint above 21 K were annealed in a vacuum in the temperature range 500-700~ for 42 h. Small decreases (less than 0.5 K) in both Tc.o.…”

Section: Influence Of Gas Flow Rates On Superconducting Transition Tementioning

confidence: 99%

Preparation of Nb3Ge films by chemical transport reaction and their critical properties

Oya

Saur

1979

J Low Temp Phys

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Niobium-germanium films have been deposited on sapphire substrates at 900~ by a chemical transport reaction method. The highest superconducting transition onset temperature Tc.o, of 22.4 K is observed for a nearly stoichiometric Nb3Ge film with the A 15-type structure (thickness ~ 93.5 tzm). Lattice constants for the Nb3Ge phase formed in the Nb-Ge films with both Tc,o,, above 22 K and Tc,miapoim above 21 K are found to extend from 5.143 to 5.153 A. Deposition rates for the obtained films are in the range of 2-10 lxm/min. Critical current densities for the Nb~Gejfilm with the highest Tc,o,, value are observed to be relatively low (~ 10 A/cm 2 at 19K at self-field). This is due to the coarse grain structure of the film or the low density of effectual pinning centers in the film. Field variations of the pinning forces operating in this film in magnetic fields both parallel to the film surface and perpendicular to the film surface are found to follow closely b l/e(1 -b) e, to which the pinning force for flux pinning at the surface of normal regions, such as grain boundaries, film surfaces, etc., is proportional, and where b is the reduced magnetic induction (B/Bc2). A small increase in Jc at low fields is caused by the presence of a small amount of the NbsGe3 phase in a Nb3Ge film, and seems attributable to additional flux pinning on NbsGe3-phase particles in the film.

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“…1,2,3 The relationship between structural instability and conventional superconductivity, manifested through structural phase transitions at low temperatures, has long been discussed from the physics perspective in intermetallic compounds such as the A15 and Laves phases. 4 Similarly, superconductivity has recently been found in many iron pnictides in the shadow of a suppressed low temperature structural phase transition in their ThCr2Si2 structure type hosts; even though the mechanism for the superconductivity appears to involve much more than electron-lattice coupling, it is not likely that the superconductivity and structural phase transitions are unrelated. 5 Thus knowing that superconductivity in the ThCr2Si2 structure type can occur near a structural transition, we set out to explore further the concept that superconductivity and structural instability can go hand-in-hand in intermetallics by considering this relationship from a different perspective: for a case where structural instability is reflected through polymorphism rather than through the presence of a temperature-dependent structural phase transition.…”

mentioning

confidence: 96%

The New Superconductor tP-SrPd₂Bi₂: Structural Polymorphism and Superconductivity in Intermetallics

2016

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ABSTRACT:We consider a system where structural polymorphism suggests the possible existence of superconductivity through the implied structural instability. SrPd2Bi2 has two polymorphs which can be controlled by the synthesis temperature: a tetragonal form (CaBe2Ge2-type) and a monoclinic form (BaAu2Sb2-type). Though the crystallographic difference between the two forms may at first seem trivial, we show that tetragonal SrPd2Bi2 is superconducting at 2.0 K whereas monoclinic SrPd2Bi2 is not. We rationalize this finding and place it in context with other 1-2-2 phases.

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Superconductivity and phase stability of Nb3Ge

Cited by 44 publications

References 20 publications

Superconductivity in NbGe2 and isostructural C-40 compounds

Superconductivity in NbGe2 and isostructural C-40 compounds

Preparation of Nb3Ge films by chemical transport reaction and their critical properties

The New Superconductor tP-SrPd₂Bi₂: Structural Polymorphism and Superconductivity in Intermetallics

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Superconductivity and phase stability of Nb3Ge

Cited by 44 publications

References 20 publications

Superconductivity in NbGe2 and isostructural C-40 compounds

Superconductivity in NbGe2 and isostructural C-40 compounds

Preparation of Nb3Ge films by chemical transport reaction and their critical properties

The New Superconductor tP-SrPd2Bi2: Structural Polymorphism and Superconductivity in Intermetallics

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The New Superconductor tP-SrPd₂Bi₂: Structural Polymorphism and Superconductivity in Intermetallics