Influence of hydrogen on the thermal conductivities of superconducting Nb and Ta

We report on magnetic and magnetoresistance measurements in two categories of superconducting Nb films grown via magnetron sputtering and MgB−2 bulk samples. In the first category, films of Tc = 9.25 K were produced by annealing during deposition. In these films, the magnetic measurements exhibited the so-called "second magnetization peak" ("SMP"), which is accompanied by thermomagnetic instabilities (TMI). The characteristic field H fj , where the first flux jump occurs, has been studied as a function of the sweep rate of the magnetic field. Interestingly, in the regime T < 6.4 K, the respective line H fj (T ) is constant, H fj (T< 6.4 K)= 40 Oe. A comparison to TMI observed in MgB2 bulk samples is also performed. Our experimental findings can't be described accurately by current theories on TMI. In the second category, films of Tc = 8.3 K were produced without annealing during deposition. In such films, we observed a peak effect (PE). In high magnetic fields the PE is accompanied by a sharp drop and a narrow hysteretic behavior (∆T < 20 mK) in the measured magnetoresistance. In contrast to experimental works presented in the past, the comparison of our magnetic measurements with the magnetoresistance data suggests that rather the appearance of surface superconductivity than the melting transition of vortex matter, is the cause of the observed behavior.

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“…In the superconducting state (3 K< T < T c2 (H)) the exponent κ takes the values 1 < κ < 3 [45]. By assuming the general relation…”

Section: Resultsmentioning

confidence: 99%

“…For Nb the thermal conductivity is described by the relation κ(T ) ≈ κ o T κ . In the superconducting state (3 K< T < T c2 (H)) the exponent κ takes the values 1 < κ < 3 [45]. By assuming the general relation…”

Section: Comparison With Theorymentioning

confidence: 99%

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB₂bulk samples

Σταμόπουλος¹,

Speliotis²,

Niarchos³

2004

Supercond. Sci. Technol.

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“…There is now a lot of experimental evidence for hydrogen tunnelling in niobium. Specific heat [ 1 ], thermal conductivity [2,3] and anelastic relaxation [4] exhibit some unusual properties which are well explained with tunnelling motions of hydrogen trapped by either oxygen or nitrogen. The presence of these two last species is necessary for the observation of the hydrogen tunnelling [4,5].…”

Section: Classificationmentioning

confidence: 96%

Effect of the hydrogen tunnelling states of the acoustic wave propagation in niobium at low temperatures

Bellessa

1983

J. Phyique Lett.

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“…Furthermore, it is known that interstitial type defects will have associated with them an additional mechanism by which phonons can be scattered in a solid [42]. Most notably, in the case of filled clathrates and filled skutterudites a "guest" atom or molecule is loosely bound and free to oscillate (or "rattle") within a void created by the host structure, and can lead to a marked reduction in thermal conductivity [6,43e45].…”

Section: Resonant Phonon Scatteringmentioning

confidence: 99%

Low thermal conductivity in nanocrystalline Zn3P2

Thompson

Vaddi

White

2016

Journal of Alloys and Compounds

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a b s t r a c tSemiconductors with low lattice thermal conductivity are important in the search for more efficient thermoelectric materials. The thermal conductivity of nanocrystalline (<7 nm) Zn 3 P 2, fabricated in thin film form by pulsed laser deposition, was measured from 80 K to 294 K. The thermal conductivity of the film showed weak temperature dependence in this temperature range and at 294 K had its highest value of 0.49 W/m K. Although Zn 3 P 2 and its family of isomorphic compounds are known to have intrinsically low thermal conductivity, at room temperature the thermal conductivity of this nanocrystalline film is 25% smaller than the calculated minimum thermal conductivity for Zn 3 P 2 . Analyzing the thermal conductivity data with the Callaway model revealed that the data could be well fit by considering only boundary scattering and point defect scattering. The boundary scattering length was in good agreement with the film's average crystallite size of 4.1 nm and the magnitude of the point defect scattering required the formation of V Zn -Zn i pairs from approximately 23% of the Zn sites. It is believed that a large number of point defects are responsible for the intrinsically low thermal conductivity of bulk Zn 3 P 2 and therefore the exceptionally low thermal conductivity found in the present study results from the nanometer dimensions of the crystallites. As previous studies have reported high Seebeck coefficients and electronic properties that are insensitive to grain boundaries in Zn 3 P 2 , the low thermal conductivity observed in the present study suggests that nanocrystalline Zn 3 P 2 should be further explored for use in thermoelectric applications.

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Influence of hydrogen on the thermal conductivities of superconducting Nb and Ta

Cited by 51 publications

References 17 publications

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB₂bulk samples

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB₂bulk samples

Effect of the hydrogen tunnelling states of the acoustic wave propagation in niobium at low temperatures

Low thermal conductivity in nanocrystalline Zn3P2

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Influence of hydrogen on the thermal conductivities of superconducting Nb and Ta

Cited by 51 publications

References 17 publications

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB2bulk samples

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB2bulk samples

Effect of the hydrogen tunnelling states of the acoustic wave propagation in niobium at low temperatures

Low thermal conductivity in nanocrystalline Zn3P2

Contact Info

Product

Resources

About

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB₂bulk samples

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB₂bulk samples