Abstract:A systematic study of the weak-link behavior for YBa 2 Cu 3 O 7-δ polycrystalline samples has been done using the electrical resistivity and AC susceptibility techniques.The experiments were performed with two samples of similar grain, a sample of wellcoupled grains, and a deoxygenated sample in such a way that the oxygen mostly come from the intergrain region. Analysis of the temperature dependence of the AC susceptibility near the transition temperature (Tc) has been done employing Bean's critical state mode… Show more
“…It is well-known that the high-T c granular superconductors having a well defined superconducting transition temperature, generally display a two step resistive transition ρ(T) and, correspondingly, dρ/dT displays a peak and a tail in the lower temperature side [47][48][49].…”
In this study, Na substituted Bi 2 Sr 2 Ca 0.9 Na 0.1 Cu 2 O superconductor samples were prepared by a polymer solution method. Three different sintering temperatures (850, 860, and 870
“…It is well-known that the high-T c granular superconductors having a well defined superconducting transition temperature, generally display a two step resistive transition ρ(T) and, correspondingly, dρ/dT displays a peak and a tail in the lower temperature side [47][48][49].…”
In this study, Na substituted Bi 2 Sr 2 Ca 0.9 Na 0.1 Cu 2 O superconductor samples were prepared by a polymer solution method. Three different sintering temperatures (850, 860, and 870
“…For temperatures between the end of the peak in and c T for a given measuring field, the grains are decoupled, while below p T the grains are coupled. This coupling permits the real part of susceptibility to reach 1 (SI) in small fields [35].…”
Section: Resultsmentioning
confidence: 99%
“…The value of n is 2 for superconductor-normal metal-superconductor (SNS) junctions [40] and 1 for superconductorinsulator-superconductor (SIS) junctions [41]. The values of n between 1 and 2 indicate the formation of superconductor-insulator-normal metalsuperconductor (SINS) junctions [35]. .…”
Superconductor samples of type (CoFe 2 O 4 ) x GdBa 2 Cu 3 O 7δ (0≤x≤0.1) were synthesized by the conventional solid-state reaction technique, whereas nanosized CoFe 2 O 4 was prepared by co-precipitation method with grain size of about 8.5 nm. The elemental content of the prepared samples was determined using particle induced X-ray emission (PIXE). The temperature dependence of real ( ) and imaginary ( ) components of AC magnetic susceptibility (ACMS) at different magnetic field amplitude (3-15 Oe) was investigated. The analysis of the temperature dependence of ACMS was performed using Bean critical state model. The values of the critical current density c J at T > p T ( p T is the inter-granular loss peak temperature) were calculated as a function of magnetic field and nanosized CoFe 2 O 4 content. It was found that the low nanosized CoFe 2 O 4 addition content (x = 0.01) improves the critical current density c J of Gd-123 superconducting phase. The observed variation of c J with temperature indicated that the weak links are changed from superconductornormal metal-superconductor (SNS) for free sample to superconductor-insulator-superconductor (SIS) type of junctions for samples added with nanosized CoFe 2 O 4 of x > 0.01. We also discussed the experimental results in the framework of the critical state model to estimate the effective volume fraction of the grains g f using Cole-Cole plots.
“…The XRD results show that a small increase of 5 °C above 865 °C in the annealing temperature (865 °C, sample F) leads to a notable degradation of the superconducting properties due to the formation of some unknown phases. It is known that the high-T c granular superconductors having a well defined superconducting transition temperature generally display a two step resistive transition ρ(T) and correspondingly the derivative of the ρ(T) displays a peak and a tail in the lower temperature side [5,6]. The peak temperature marks the superconducting transition within the grains and the tail is related to the intergranular coupling.…”
mentioning
confidence: 99%
“…The value of n is 2 for Superconductor-Normal metal-Superconductor (SNS) junctions [11], and 1 for SuperconductorInsulator-Superconductor (SIS) junctions [12]. The values of n between 1 and 2 indicate the formation of Superconductor-Insulator-Normal metal-Superconductor (SINS) junctions [5].The respective values of n for best fitting are given in Table 1. As one can see from Table 1 by increasing sintering temperature from 830-865 °C the corresponding weak links changes from SIS type for sample A to SNS type for sample E.…”
We have studied the effect of sintering temperature on the weak link behavior of polycrystalline Bi2223 superconductors with different intergranular coupling using the XRD, electrical resistivity and AC susceptibility techniques. The XRD results show that by increasing sintering temperature up to 865 °C the Bi2212 phase fraction decrease. It was found that the Bi2212 phase on the grain boundaries is likely to play the role of weak links and consequently reduces the intergranular critical current densities.
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