Effect of K-doping to the weak link behaviour of (Cu0.5Tl0.5−xKx)Ba2Ca2Cu3O10−δ superconductors
01 Jan 2010-Physica C-superconductivity and Its Applications (North-Holland)-Vol. 470, Iss: 1, pp 51-54
TL;DR: In this paper, a systematic study of the weak link behavior for (Cu 0.5 Tl 0.25 K 0.6 Tl ) superconductors has been carried out using electrical resistivity and AC-susceptibility techniques, and it is concluded from these studies that potassium atoms appearing at the crystal boundaries enhance inter-grain coupling and pinning mechanism in K-doped (Ba 2 Ca 2 Cu 3 O 10− δ ) supercondors.
Abstract: A systematic study of the weak link behaviour for (Cu 0.5 Tl 0.5− x K x )Ba 2 Ca 2 Cu 3 O 10− δ ( x = 0, 0.25) superconductors samples has been carried out using electrical resistivity and AC-susceptibility techniques. The K-doped (Cu 0.5 Tl 0.5− x K x )Ba 2 Ca 2 Cu 3 O 10− δ samples were synthesized by solid-state reaction method. In magnetic susceptibility measurements, the real ( χ ′) and imaginary ( χ ″) parts of the magnetic susceptibility of (Cu 0.5 Tl 0.5− x K x )Ba 2 Ca 2 Cu 3 O 10− δ ( x = 0, 0.25) samples were measured as a function of temperature under various DC-magnetic fields up to 172 Oe. It is observed from these studies that the magnitude of the diamagnetism is substantially enhanced by K-doping. The possible reasons for the enhanced magnitude of diamagnetism have been investigated. It is observed from in-field magnetic measurements that the inter-grain coupling is improved with the K-doping. It is concluded from these studies that potassium atoms appearing at the crystal boundaries enhance inter-grain coupling and pinning mechanism in K-doped (Cu 0.5 Tl 0.25 K 0.25 )Ba 2 Ca 2 Cu 3 O 10− δ superconductors.
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TL;DR: In this article, nano-particles of CuO, BaO and CaO2 were added to polycrystalline (Cu0.5Tl 0.5)Ba2Ca2Cu3O10−δ superconductors.
Abstract: Polycrystalline (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ superconductors show strong composition variations at the termination ends of the crystals which compromise over-all superconducting properties of the final compound. These composition variations are one of the root causes of void formation which produces a poor quality material. The better inter-grain coupling suppresses the Josephson losses required for higher transport critical current density (J c ). The lower losses across the inter-grain Josephson junctions are essential for wire and microelectronic applications. We have fixed such inadvertent composition variation in (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ superconductors by doping them with nano-particles of CuO, BaO and CaO2. Nano-particles doped (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ superconductors were synthesized at 860 °C and characterized using X-ray diffraction (XRD), resistivity (ρ), ac-susceptibility (χ), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) measurements. The magnitude of superconductivity is significantly enhanced with the doping of nano-particles. The samples with 15 wt. % addition of CuO nano-particles have even shown textured elongated crystalline with extremely low population of voids.
20 citations
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TL;DR: In this paper, the Ginzburg-Landau theory was employed to calculate important superconductivity parameters, such as the flux pinning characters and the inter-layer coupling of CuO2 planes.
Abstract: Cu0.5Tl0.5Ba2Ca n−1Cu
n
O
2n+4−δ
(n = 2, 3, 4) thin film samples have been investigated for excess conductivity analysis (fluctuation-induced conductivity (FIC)). The thin films are c-axis oriented and have shown the tetragonal structure in which the T
c (R = 0) of the samples increases with an increasing number (n) of the CuO2 planes. The FIC analysis is carried out by following the Aslamazov-Larkin theory and in the critical regimes from the Ginzburg-Landau number. By employing the Ginzburg-Landau theory, we have calculated important superconductivity parameters. The values of ξ
c(0), VF, and τ
φ
increase, but the inter-layer coupling (J) of CuO2 planes is suppressed with the increasing number of CuO2 planes in these samples. The λ
pd, however, is suppressed, but the values of B
c(T), B
c1(T), and J
c(0) increase with the increasing number of conducting planes in Cu0.5Tl0.5Ba2Ca n−1Cu
n
O
2n+4−δ
(n = 2, 3, 4) samples. This demonstrates the increase in flux pinning characters that is most likely induced by thallium defects in the charge reservoir layer.
6 citations
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TL;DR: In this paper, the authors studied the properties of Cu0.5Tl 0.5Ba2Ca3Cu4O12−δ samples synthesized by two-step solid-state reaction method and showed that the energy of activation derived from the slope of Log(Jc) vs. reduced temperature enhances with the increase strength of applied field.
Abstract: Flux pinning characteristics of Cu0.5Tl0.5Ba2Ca3Cu4O12−δ samples synthesized by two-step solid-state reaction method have been studied by physical properties measurement system (PPMS). These thin films are oriented along c-axis and have shown the tetragonal crystal structure. In the resistivity measurements, these samples have shown Tc (R = 0) around 106 K. Asymmetric M vs. H loop of the samples at various temperature shows the interaction bulk and surface pinning. The energy of activation derived from the slope of Log(Jc) vs. reduced temperature enhances with the increase strength of applied field. The irreversibility field suppress with the increase in the measurement temperature. The pinning energy per unit length of flux votex e and the de-pinning force also suppress with increase of measurement temperature. The Hc1, Hc, and Hc2 (hence the Hirr) are suppress with the increase of measurement temperature, since the Hc determines the free energy difference between the normal and superconducting state. The increase in the Hc at lower temperature shows that the density of superconducting electrons increases with the suppression of temperatures. The enhancement in the density of superconducting carriers at low temperatures would increase the coherence length and suppress the population of flux vortices. It can be seen in the form of decreased values of Ginzburg Landau parameter κ and the penetration depth λD.
5 citations
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TL;DR: In this paper, the authors review the laser absorption, correlated evaporation, molecular dissociation, and the crystallographic effects on the field eva-oration of 800-m conductors.
Abstract: In the field of high-temperature superconductors, atom probe tomography is a relatively new instrument, with the ability to provide a new perspective on the 3D nanoscale microstructure. However, field evaporation of nonmetallic materials is fraught with unique challenges that matter little in the world of metallic evaporation. In this study, we review the laser absorption, correlated evaporation, molecular dissociation, and the crystallographic effects on the field evaporation of 800-m
${\rm RB}{\rm a}_ 2{\rm C}{\rm u}_ 3{\rm O}_{ 7-{\rm \delta }}$
(R = Gd, Sm) coated conductor tapes deposited by Reactive Co-Evaporation Cyclic Deposition and Reaction (RCE-CDR). Ultraviolet 355 nm laser pulsing was found to have a substantial beneficial effect on minimizing the fracture probability compared with 532 nm illumination, especially when evaporating insulating oxide precipitates. This, in turn, allows for the 3D compositional analysis of defects such as flux pinning centers introduced by precipitation and doping. As a result, evidence for the precipitation of nanoscale
${\rm G}{\rm d}_ 2{\rm C}{\rm u}_ 2{\rm O}_ 5$
is discussed. The effect of crystallographic orientation is studied, where [001] aligned evaporation is found to develop compositional aberrations.
2 citations
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Abstract: The effect of Na substitution on the formation and superconductivity of Tl-1212-type phase (Tl0.85Cr0.15)Sr2−xNaxCaCu2O7 (x = 0–0.30) is reported. The samples were prepared via the solid-state reaction method. X-ray diffraction patterns showed the presence of Tl-1212-type phase or Ca0.3Sr0.7CuO2 (CSCO) as a major or minor phase in the samples. The resistance versus temperature curves showed onset transition temperature, Tc-onset between 97 and 106 K and zero-resistance temperature, Tc-zero between 88 and 99 K. AC susceptibility measurement showed superconducting transition $${T_{{\text{c}}{\chi ^\prime }}}$$ between 89 and 98 K. The peak temperature, Tp, of the imaginary part of the susceptibility, χ″, was the highest for x = 0.02 sample (Tp = 96 K). The inter-grain critical current density, Jc, at Tp for x = 0 sample was Jc (Tp = 68 K) = 14 A cm−2 and for x = 0.02, 0.20 and 0.30 Jc (Tp) at 96, 96, and 88 K, respectively, is 19 A cm−2. Na substitution increased the grain size of the Tl-1212 samples. All Na-substituted samples showed higher transition temperature, enhanced critical current density, and improved inter-grain coupling compared with the non-substituted sample. This work showed that other than rare-earth elements, monovalent alkali metal such as Na could also be used to enhance the superconducting properties of the Tl-1212 phase.
2 citations
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