Effect of deoxygenation on the weak-link behavior of YBa2Cu3O7−δ superconductors

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 model. The observed variation of intergranular critical current densities(Jc) with temperature indicates that the weak links are changed from superconductor-normal metal-superconductor (SNS) for well-coupled sample to superconductor-insulatornormal metal superconductor(SINS) type of junctions for the deoxygenated sample.These results are interpreted in terms of oxygen depletion from grain boundaries, which in turn decreases the intergranular Josephson coupling energy with a consequent decrease of pinning of the intergranular vortices.

Sintering Effects in Na-Substituted Bi-(2212) Superconductor Prepared by a Polymer Method

“…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].…”

The effect of nanosized CoFe2O4 addition on the magnetic properties of GdBa2Cu3O7-δ using AC magnetic susceptibility measurements

“…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].…”

“…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]. .…”

The effect of sintering temperature on the weak link behavior of Bi‐2223 superconductors

“…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.…”

“…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.…”