Study On Capturing Flux Performance Of YBCO High Temperature Superconducting Block

Since the discovered of high-temperature superconductors in1986, great of works have been done on the fabrication, properties and applications on the YBCO bulk superconductors. In order to make superconducting materials have better performance, people have being not only work on research and look for new superconductors with higher transition temperature, but also continuously work on the performance improvement of the discovered superconductors with practical potential. Modification of processing method and the second phase particles doping are the two most common and effective ways used for large-size and high-quality YBCO superconductor.There are two methods for the preparation of YBCO superconducting bulk, including Top Seeded Melt Texture Growth(TSMTG) as well as Top Seeded Infiltration and Growth Process(TSIG). These two methods have advantages and disadvantages. A Modified TISG process was used for the fabrication of YBCO bulk superconductors, a mixed powder of Y2O3, BaCuO2and CuO was chosen to instead of traditional mixed powder of YBa2Cu3O7-δ and Ba3Cu5O8as liquid phase; a mixed powder of Y2O3+xBaCuO2was selected to replace of the traditional Y211as new solid phase. Single domain YBCO superconductors with diameter of20mm and30mm have been fabricated using this new method. The new process can greatly simplify the fabrication process of YBCO superconductors and reduce the manufacturing cost, because of only kind of BaCuO2powder is need to prepare.The high or low of the trapped field is closely related with the flux pining force of YBCO bulk superconductors and the magnetization methods. The effects of pulse field magnetization ob the trapped field of single domain YBCO bulk superconductors have been investigated.In this paper, all the YBCO bulk superconductors were magnetized at77K, zero-field cooling state during the pulse magnetization process. The effect of the peak value of pulsed magnetic field on the trapped flux density and distribution have been studied, the results show that the strength of the trapped flux density increases with the increases of the peak value of the pulsed magnetic field, such as when the peak value of the pulsed magnet field increases from2.83T to5.96T, the captured flux density of YBCO bulk increases from0.128T to0.303T. Then, the trapped flux density decreases rapidly with the increasing of peak value of the pulsed magnet field, such as when the peak value of the pulsed magnet field increases from5.96T to7.15T, the captured flux density of YBCO bulk increases from0.303T to0.125T. The result indicated that, too weak or too strong of the peak value of the pulsed magnetic field will lead to a relatively lower trapped flux density, only proper peak value of the pulsed magnetic field is able to obtain a maximum trapped flux density.The effect of the magnetization times on the trapped flux density and distribution have been studied at77K and zero-field cooling state, with fixed peak value of pulsed magnetic field during the pulse magnetization process, the results show that if the peak of pulsed magnetic field is low, after the first magnetizing, superconductors can capture low intensity of magnetic field. Afterwords, with the times of magnetizing increasing, the capacity of superconductors increases gradually, to saturation value. But if peak value of the pulsed magnet field is of the optimal value to obtain a maximum trapped field in single magnetizing, the result is different from the previous case, it is found that the highest trapped flux density can be achieved by the first magnetization, later the trapped flux density of the single domain YBCOsuperconductor gradually decreases with the increasing magnetizing times, and final tends to a relatively saturated low trapped flux density.These consequences show that the density and distribution of trapped flux density the single domain YBCO superconductor is not only relative to the peak value of the pulsed magnet field、the pulse width、the time of pulse and the way of pulse, but also related with the temperature of magnetize、gradient of the magnetic field、the temperature rise during pulsed field magnetization、magnetic stress and thermal stress during pulse field magnetization. Therefore, in order to obtain the best trapped flux density in single domain YBCO superconductor, a lot of research is still need to be done to optimize relative technical parameters to optimize the pulse field magnetization method.