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The important factors in obtaining a high-quality superconducting joint were investigated for the superconducting joint of a GdBa2Cu3Ox (GdBCO) bulk superconductor with sintered ErBa2Cu3Ox (ErBCO) using the local melt-growth method. REBCO (RE: rare earth) bulk superconductors can be used as strong magnets by magnetizing them, but they require large bulk sizes for their application. Although the superconducting joint presents a viable solution, many possibilities for property improvement remain, such as property degradation, depending on the joining direction. By varying the joining thermal conditions and confirming the elemental distribution, magnetization properties near the joined part and the effects of these on the joining properties are clarified, and a method for fabricating high-performance joined samples is obtained. Microstructure segregation was rarely observed at the center of the joined part regardless of the joining direction, and the superconducting properties were negligible and small. The Jc-B results are almost identical to those of the GdBCO matrix at a low field, confirming that the joined part minimally interferes with the superconducting current. Furthermore, by lowering the maximum temperature, shortening the holding time at the maximum temperature, and increasing the cooling rate, the region of mutual solid solution was reduced, and the Jc-B under the self-magnetic field was enhanced. These results contribute to the development of the superconducting joining method, a critical aspect of larger bulk superconductors. [ABSTRACT FROM AUTHOR]

The aim of this study is to improve the connectivity and microstructural control of bulk MgB2 via admixed in situ and ex situ syntheses and their effect on flux pinning behavior. Different weight percentages with the ratio of x wt.% ex situ powder were added to 1.0 g in situ powder via a solid state synthesis process where x = 0, 15, 20, 25, and 30, respectively. MgB2 was verified as the predominant phase in all of the samples by X-ray diffraction. With the addition of ex situ powder, magnetization measurements revealed a modest drop in critical temperature, Tc, from 38.5 to 37.8 K. At 20 K, the self-field critical current density, Jc, increased as the co-addition levels increased, owing to enhanced grain coupling. With a 20 wt.% co-addition level, the largest self-field Jc achieved is 348 kA/cm2 showing field dependent Jc of the co-added samples at 20 K is greater than that of the pure sample. The current findings suggest that a small quantity of ex situ powder added to the admix portion of Mg and 2B during synthesis can improve flux pinning and Jc. The reduction in the void volume which enhanced the connectivity of the sintered bulk samples was observed by scanning electron microscopy. Our results show that ex situ-in situ co-synthesis develops the superior connectivity potential of MgB2 bulk superconductor. [ABSTRACT FROM AUTHOR]

The analysis explains the effects of [ZrO.sub.2]/[SnO.sub.2] nano-particles on the superconducting properties and microstructure of melt-processed Gd{ba.sub.2][Cu.sub.3][O.sub.7-[delta]] (Gd123) superconductors. The excessive addition is found to suppress the properties of these superconductors.

Fracture toughness of SmBaCuO bulk superconductors is investigated by Vickers hardness test at cryogenic temperatures. The experimental procedure and test results are described.

The effects of test temperature and Sm211 secondary phase particles on the fracture toughness of the Sm123 single grain bulk superconductors are examined by tensile and bending tests using the v-notched specimens. The experimental procedure and test results are discussed.

Investigating the E-J characteristics over a wide range of E-J for the Nd123 with remarkable secondary peak and the Y123 with smaller secondary peak by combining the dc magnetization and the ac susceptibility with the aim of clarifying the relation between the n value and the field-induced pinning is discussed. The results show that the melt-textured Nd123 with the large n value has an advantage for many high field applications at 77 K.