Quasi Single Domain Melt Texture Ybco Bulk Technology And Performance Studies

Fusion reactors are considered to be one of the most potential new energysources, and the fusion material is very important in fusion reactor's realization.Themagnet furnace for the thermal nuclear reaction in fusion reactors is necessary,so thelarge scale superconducting magnet is the most appropriate candidate material for thenuclear fusion reactions.the superconductor has a characteristic of zero resistance andhaving no power to be input.They produce fields which is not only high but alsoextremely homogeneous spatially and temperally stable,so the application of hightemperature superconductors becomes more and more widespred,such as high energyphysics,energy conversion,power transmission and nuclear magnetic resonance (NMR)spectroscopy of bilmolecules.The high quality superconductors to be found andrealized are an more attractive project in physical fieldsThis paper describes the method of artificial doping Y-211phase and melt-texturedgrowth (MTG) with a top-seeded technique to prepare the quasi-single crystal domainYBCO bulk materials with various Y-211particle contents.Used the improvingexperimental method and controled the accurate techonology parameters,the fluxpinning capability was enhenced for the YBCO bulk materials.At same time,theflux pinning mechanism was also explored.The obtained specimens with 20mm in diameter and 2mm in thickness, have highdensity (more than 6.2g/cm～3) and good mechanical toughness. In the field range -5-+5Tesla,the VSM was used to measure the magnetization curves of specimens atl0K and 30K respectively when the applied fields along the c axis of thespecimens,the altem current suscibility method was also adopted to measue thecritical temperature transition curves in a field of l0Oe.The results show that thehighest T_c for the specimen is about 91.5K,the transition width is lower than1K,which suggest that the specimens consist of a nearly homogeneous YBa₂Cu₃O₇phase.On the basis of magnetization curves,according to the Bean-Model calculatedthe J_c,the J_c of specimens reaches 2.14×10～6A/cm～2 and 1.23×l0～6A/cm～2 under 0.6 Teslaat l0K and 30K, 1.35×10～4A/cm～2 under 2 Tesla at 70K,and the critical current densityis unsenstive to the fields. The SEM observation ofspeclmens Indicates that Y－211 particles can improve thequality ofMelt－textured YBCO superconductor and reduce the mlcrocrack ofspecimens．Therefore,the Y211 phase are believed not only to serve as nucleation sliesforY－123 phase but also to e汕encethe growth alongthe c axis,lthas also beenobserved that iner Y－2lip�'�Ides lead to a more frequent的er formation·Combining the mlcrostructures with Jcmeasurements shows that the smaller theParticle size,the more homogeneous the paftlcle dlstrlbutlon,the hlgherthe plnLninge肚ctlveness．Therefore,luxs are mainly pinned the血erface betweenthe YZllp�'�Ides and the matrix materials where the gradient In free energy Is a maximum．The best ratio ofy－123 to Y－211 forthe superconductor specimens Isl:0．5 In moles,In毗ichthe Y－211瞅Ides are uniformly distrlMed and their size Is about 200 urn．...