Dynamic control for the direct measurement of transport critical current in superconductors

We study the hysteresis and relaxation of both intragranular and intergranular properties of TlBa 2 Ca 2 Cu 3 O y (Tl-1223) superconducting polycrystals between 80 and 120 K. The samples have been prepared using a technique involving the mixing of grains of different sizes before the final sintering. The grains show a sizeable reversible magnetization, while vortices inside the grain behave as three-dimensional objects. The transport critical current is strongly hysteretic, with features that distinguish our Tl-1223 samples from 'standard' YBa 2 Cu 3 O 7−δ (YBCO), (Hg, Re)Ba 2 Ca 2 Cu 3 O 8+δ (HBCCO) and (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O 10−δ (BSCCO) polycrystals. The preparation method improves the transport properties of the samples. The relaxation of the transport critical current density, in the presence of trapped fields, is reported here for the first time in this system, as far as we know. A phenomenological model can qualitatively describe the transport properties, where the intragrain magnetization affects the intergranular junctions, but a precise quantitative description is not achieved. The differences in the shape of the transport measurements, for different polycrystalline systems, are also well described by the model.

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“…The transport measurements were performed in an experimental set-up described elsewhere [10], and can be classified as follows.…”

Section: Measurementsmentioning

confidence: 99%

Hysteresis and relaxation in TlBa₂Ca₂Cu₃O_ysuperconducting polycrystals

Batista-Leyva

Cobas

Orlando

et al. 2003

Supercond. Sci. Technol.

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“…Transport Measurements. Electrical resistivity versus temperature measurements were performed in an automatic installation, described elsewhere [17]. The measurement procedure and data processing were similarly reported [18].…”

Section: Methodsmentioning

confidence: 99%

Effects of Oxygen Doping on the Transport Properties of Hg0.82Re0.18Ba2Ca2Cu3O8+d Superconducting Polycrystals

Passos

Rocha

Bolzan

2014

AMR

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Hg0.82Re0.18Ba2Ca2Cu3O8+dpolycrystalline ceramic samples were prepared using a solid-vapour reaction technique. First, the ceramic precursor was prepared from a mixture of Ba2Ca2Cu3Oxand ReO2powders in a molar ratio of 1:0.18. The precursor material was annealed under three different partial pressures of oxygen that consisted of a mixture of oxygen/argon in the following ratios: 5/95 (sample A), 10/90 (sample B) and 15/85 (sample C). Secondly, the precursors prepared at different O2partial pressures were blended with HgO at a molar relationship of 1:0.82. The synthesis was carried out at 865 °C for 72 h. Moreover, analyses using X-ray powder diffraction, Scanning Electron Microscopy (SEM), and Energy Dispersion X-ray spectroscopy (EDS) were performed. These results demonstrated a similarity in the grain morphology within the samples. Using SEM images, a histogram of grain-boundary size was produced where the average junction size is represented by a gamma density distribution function. Finally, the samples were submitted to ac electrical resistivity ρ (T) under a low applied magnetic field (up to 400 Oe). Samples cut into bars approximately 7 × 1 × 1 mm3in size were studied using a four-probe technique. The zero-resistance critical temperatures (Tcj) were determined from ρ (T) curves. The results are compared and qualitatively explained in the framework of flux trapping by superconducting grains. In our opinion, the oxygen partial pressure has a strong influence on the grain junctions and causes island structures that form defects at the grain boundaries.

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“…This provokes the integrator output to start to sweep down (at the same rate) until the current through the sample reaches −I m . At this point the initial situation is repeated but only until I b equals zero and the integrator is re-set during a pre-determined time (T d ) in order to avoid sample heating by contact dissipation [5,6]. The signal current's waveform is shown in figure 1(b).…”

mentioning

confidence: 99%

A multichannel averager technique for current-voltage measurements in high- superconductors

Martínez¹,

Flores²,

Hernandez³

1998

Meas. Sci. Technol.

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A computer-controlled technique was developed to measure the current-voltage dependences in high-T c superconductors. The system is based on the multichannel averaging technique. The current through the sample follows a triangular bipolar waveform and is measured by a data acquisition board to be used as an index to a memory array in which the sample voltage is to be averaged. Applying this principle, the noise level present in the sample voltage virtually does not matter. The desired signal will build up, from the noise, proportional to the square root of the number of scans. The main advantage of this technique is the simple and inexpensive hardware requirements.

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Dynamic control for the direct measurement of transport critical current in superconductors

Cited by 11 publications

References 5 publications

Hysteresis and relaxation in TlBa₂Ca₂Cu₃O_ysuperconducting polycrystals

Hysteresis and relaxation in TlBa₂Ca₂Cu₃O_ysuperconducting polycrystals

Effects of Oxygen Doping on the Transport Properties of Hg<sub>0.82</sub>Re<sub>0.18</sub>Ba<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>8+d</sub> Superconducting Polycrystals

A multichannel averager technique for current-voltage measurements in high- superconductors

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Dynamic control for the direct measurement of transport critical current in superconductors

Cited by 11 publications

References 5 publications

Hysteresis and relaxation in TlBa2Ca2Cu3Oysuperconducting polycrystals

Hysteresis and relaxation in TlBa2Ca2Cu3Oysuperconducting polycrystals

Effects of Oxygen Doping on the Transport Properties of Hg<sub>0.82</sub>Re<sub>0.18</sub>Ba<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>8+d</sub> Superconducting Polycrystals

A multichannel averager technique for current-voltage measurements in high- superconductors

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Hysteresis and relaxation in TlBa₂Ca₂Cu₃O_ysuperconducting polycrystals

Hysteresis and relaxation in TlBa₂Ca₂Cu₃O_ysuperconducting polycrystals