Study On Technology Searching And Microstructure Analysis Of YBCO Superconductors Made By Directional Solidification

Due to the high transition temperature and the quite high critical current density ,the YBa2Cu3o7-δ (YBCO or Y123) superconductor can be applied for many potential aspects i such as superconducting magnetic suspension, superconducting motor and superconducting flywheel. It is important that a superconductor with a kind of orientation crystal must be obtained so that it has an available critical current density. A research, which is preparing high temperature superconductor with stronger anisotropism by the unidirectional solidification method, is being paid more attention. This technology can make the microstructure of material to be aligned exactly along with the preferential orientation and then can obtain unidirectional domains or single crystal. By the unidirectional solidification technology, the paper studied the preparation processing of the YBCO high temperature superconductor, discussed the formation mechanism of YBCO, and analyzed the microstructures obtained by different experiment parameters on theory and experiment. The main results are as follows:1. A kind of unidirectional solidification equipment for oxide was designed and made by selves. The system of the equipment mainly includes heating unit, pulling unit, and control unit, etc. The equipment is used for the unidirectional solidification processing of high critical temperature oxide superconductors. During the processing, the pulling unit can be adjusted at wide-continuous-range and work stably and reliably without the phenomena of crawling and worming under low pulling velocity.2. A suit of mould was designed and processed by selves, and then YBCO rods have been pressed successfully.3. Y123 powder was prepared by solid reaction process. Y211 powder was prepared by chemical method, and the rod precursor of YBCO was obtained.4. YBCO HTSC materials with a preferred orientation were fabricated by the directional solidification method, of which the measurement result of Tc was 92.5k, and we have experimented at different processing parameter and different component.5. The observed results of unidirectional solidification microstructures showed that lower pulling rate was favorable to the growth of high quality crystals. If the holding time is too long, the liquid tended to run off, and the 211 phase tended to grow up, that was disadvantageous to the growth of the 123 phase. The thickness of slice became thinner if the 211 particles are tiny and evenly distribution.