制备大尺寸单畴YBCO超导块材的新方法

Abstract

The top seed melt-textured growth method (TSMTG) is a most effective method for the preparation of large size single domain YBCO bulk superconductors, but suffers from sample shrinkage and serious sample deformation problems during the TSMTG process; the top-seeded infiltration growth method (TSIG) was invented to overcome these problems. However, three different powders, comprising Y2BaCuO5 (Y211), YBa2Cu3O y (Y123), and BaCuO2, must be prepared before fabrication of single domain YBCO bulk superconductors by the traditional TSIG method. This process is complicated, time-consuming, energy-consuming, and leads to atmospheric pollution, and it is also impossible to control the density and the distribution of the Y211 particles in the samples. To solve these important technical problems, we have invented a new TSIG method whereby a mixture of Y2O3 + 1.2 BaCuO2 powder is used as a new solid phase to replace the traditional solid-phase Y211, and a mixture of Y2O3, BaCuO2 and CuO powder is used as a new liquid phase rather than the traditional (Y123 + 3 BaCuO2 + 2 CuO) phase. Using this new solid phase and liquid phase, single domain YBCO bulk superconductors with diameters of 59 mm and 93 mm have been successfully prepared by the proposed TSIG process. We found that: (1) the crystal growth rate of the single domain YBCO bulks prepared by the new TSIG process is approximately 1.7 times higher than that of similar samples prepared by the traditional TSIG method; (2) the levitation force of single domain YBCO bulks prepared by the new TSIG process is 1.65 times higher than that of samples prepared by the traditional TSIG method; (3) the Y211 particles prepared by the new TSIG process are much smaller in size and have a more reasonable distribution than in the samples prepared by the traditional TSIG method, and this can effectively improve the flux pinning force of the sample. These results indicate that the new TSIG process that was developed in our laboratory is a very important and highly practical method for the fabrication of low-cost, large size, high-quality single domain rare earth BCO (REBCO)-type bulk superconductors.