Study The Technical Process Of SmBCO Superconducting Bulk Materials

REBCO high-temperature superconductor bulks, because of its high transition temperature and fine electromagnetic property, have many potential applications in superconducting maglev, superconductive critical electrical and superconducting flywheel energy storage. As the anisotropy of the crystal structure of REBCO high-temperature superconductor, to make electromagnetic property reach the level of utility, the sticking point is to grow preference-oriented crystal. Single domain YBCO superconducting bulk can be produced by using the top-seeded melt process. Top-seeded melt process can make the material grow according to the seed crystal orientation and form the c-axis oriented single domain. The SmBCO, obtained by substituting Y by the rare earth Sm in YBCO, is potentially attractive, because the SmBCO have not only a higher transition temperature (T_c) than YBCO but also a higher critical current density (J_c) in high magnetic fields. This paper studied the growth technique of the SmBCO bulk.We grow SmBCO superconducting bulk by the top-seeded melt process, studied the growth condition of SmBCO bulks systemic, in which the preparation of precursor power was also included. We also studied several factors which affect the SmBCO bulk growth, we found that the exhausting time, the melting temperature and the temperature of growing single domain are very important to the single domain SmBCO superconducting bulk growth.A new growth technology of SmBCO superconducting bulk was obtained by modifying traditional preparation technical, that is, the isothermal growth technology. It was proved that this technology enable the bulk to have a greater growth rate at the temperature of single domain growin. we confirmed that the proper growth temperature of SmBCO single domain bulk was between 1038℃and 1041℃. At the temperature above 1041℃, SmBCO can't grow integrity, and there are coarse grains and surface macro-cracks in the bulk. And at the temperature below 1038℃,the growth rate of SmBCO single domain bulk is reduced. Study found that at the temperature region between 1038℃and 1041℃, our samples have a greater growth rate along the a-b surface than it was along the c-axis. The growth rate along a-b surface is about 0.736mm/h.The MPMS was used to measure the critical temperature transition curve. It was shown that the highest T_c for our sample can reach 90.5K. According to the bean-model we calculated that the J_c of our samples can reach 0.7×10~5A/cm~2 at 30K And reach 0.7×10~4A/cm.2 at 70K with the magnetic field of 0.5 Tesla.Result indicates that a low oxygenate temperature is better for the oxygenate process of the melt-textured SmBCO bulk. A proper oxygenate temperature is between 400℃and 500℃. When the oxygenate temperature is above 600℃, the effects on T_c of specimens were reduced.