Zong-Quan Yang

Effects of nano-ZrO2 particles on the superconductivity of Pb-doped BSCCO

The major limitations of Bi-system superconductor application are the intergrain weak links and weak flux pinning capability. In order to promote the practical application of Bi-system superconductor, effective flux pinning centers must be artificially introduced into HTS to enhance the flux pinning capability. With those goals, we have investigated the effects of nanometer-sized ZrO2 addition on flux pinning capability of the bulk Pb-doped Bi-2223 by using of X-ray diffraction (XRD), DC resistivity, rho, AC susceptibility, c, and magnetic hysteresis loops measurements. We have prepared samples by Bi,Bi1.8Pb0.4Sr2Ca2.2Cu3O10+y (nano-ZrO2)(x) with x range from 0 to 0.5. The results show that, with the increasing of x-, the T-c (onset) drops down gradually. However, the measurements of the critical current density, J(c), show that appropriate amount-doped nano-ZrO2 greatly enhance the values of J(c) under magnetic fields. According to the results of XRD patterns, there are slight reflection peaks of ZrO2-related nonsuperconducting compounds. It is believed that these nonsuperconducting ZrO2-related compounds act as effective flux pinning centers

Anomalies in the M(T) curves of the ceramic superconductor Y0.8Pr0.2Ba2Cu2.90Li0.10O7−δ

Abstract In the present study, some anomalies, the paramagnetic Meissner effect (PME), the diamagnetic dip effect (DDE) in the ZFC and FC M(T) curves and the glass transition, were observed for the ceramic superconductor Y 0.8 Pr 0.2 Ba 2 Cu 2.90 Li 0.10 O 7−δ . The PME vanishes at fields higher than 5 Oe. The DDE and the glass transition peak shift to lower temperature with increasing field, accompanied by a slight broadening of DDE. All of these anomalies are discussed in relation to the Josephson coupling loops in this superconductor sample.

Irreversibility line of Tl-1223/Ag sheathed superconducting composite tape

In the present study, the irreversibility line (IL) was determined based on the ZFC and FC curves for Tl-1223/Ag sheathed superconducting tape. The IL can be well fitted to the equation H = H-0[1-T-irr(H)/T-c](n), where, H-0 equals 20.3 T, n equals 2.07 and T-c is 119 K. The fitting results, slightly different from the results on the Tl-1223 ceramic superconductor with the same composition, maybe suggest a different flux pinning mechanism in this Tl-1223/Ag superconducting tape material.

Anomalous magnetization behavior in field-cooling magnetization versus temperature curves in Tl-1223/Ag sheathed superconducting tape

The zero-field-cooling and the field-cooling temperature dependence of magnetization for Tl-1223/Ag superconducting tape were measured by using SQUID magnetometer at fields varying from 5 Oe to 5 T in the temperature range of 5–150 K. In the field-cooling curves, some anomalous behaviors, i.e., the positive Meissner effect in the curve of 5 Oe and the diamagnetic dip effect at fields up to 5 kOe, were observed. The diamagnetic dip minimum temperature shifts to the lower temperature as increasing the external field, and the relative amplitude decreases with increasing applied field. Moreover, the dip broadens with increasing applied field. The anomalous behaviors may be attributed to the flux pinning and the flux depinning of Josephson-junction networks in the sample. The dip effect at lower fields may be ascribed to the intergrain Josephson coupling networks, and that at higher fields may be due to the intrinsic intragrain Josephson coupling networks.

Laser annealing of bulk high-temperature superconductors

Abstract The results of laser annealing of bulk high-temperature superconductors YBa 2 Cu 3 O 7−x and Bi 2 Sr 2 Ca 2 Cu 3 O y are reported. It is shown that nanosecond pulsed laser treatment of superconductors without further high-temperature processing leads to increasing of critical current density of surface layers of the samples up to 3–4 order within certain interval of laser energy densities due to melting and following crystallization of thin surface layers without degradation of superconducting phase.

The property improvement of bulk high-temperature superconductors by plasma treatment

Abstract An influence of atomic oxygen exposure on the superconductivity of YBa2Cu3O7-x, Bi2Sr2Ca2Cu3O10+y and Bi2Sr2Ca1Cu2O8+z ceramics has been examined by the critical current density Jc, critical temperature Tc and X-ray diffraction measurements. It is shown that exposure of high-Tc superconductors to a low power density oxygen plasma at 473 K and 673 K leads to an increase of both Tc and Jc. The improvement of superconductivity can be explained by the passivation of dangling bonds and defects on grain boundaries of these materials.