Abstract
High-Tc superconductor (HTS) is expected to be applied to various fields because of its high critical temperature. However, the HTS is a ceramic and naturally brittle, and this disadvantage is an important issue for its applications. Therefore, the mechanical properties of the HTS must be improved to enable practical use in addition to progress in the material's superconductivity. We have studied the effect of adding ceramic fiber to Bi1.85Pb0.35Sr1.90Ca2.05Cu3.05Oy (BPSCCO) bulk. The critical current density of the ceramic fiber-added BPSCCO was lower than that of BPSCCO bulk because of the degradation of superconductivity by some compounds created during the reaction between the ceramic fiber and BPSCCO matrix. The interface between the ceramic fiber and BPSCCO matrix was not coherent, so the mechanical properties of the ceramic fiber added-BPSCCO were inferior to BPSCCO bulk. In this study, Ag wires were added into BPSCCO unidirectionally, and the samples (Ag-wire/BPSCCO) were examined. The interface condition between the Ag wire and BPSCCO matrix was better than the case of combining ceramic fiber and BPSCCO matrix. The bending strength of the Ag-wire/BPSCCO with an Ag wire weight of 15% was 72-75MPa, and the BPSCCO bulk showed a bending strength of 63-68MPa. It is recognized that Ag wire acts as a reinforcement by creating a suitable interfacial contact. Moreover, it was noticed that the Ag-wire/BPSCCO did not fracture separately and a superconductive current was able to pass through it at 77K even though a crack was induced by the three-point bending test. The Ag wire seems to increase resistance against crack propagation. The critical current densities of the BPSCCO bulk and Ag-wire/BPSCCO (30 wt% of Ag) were 141A/cm2 and 234-236A/cm2, respectively. It is considered that because the orientation of the BPSCCO grains is enhanced on the Ag wire surface, the superconductivity of the BPSCCO is improved by the addition of Ag wire.
