Control of Ag Distribution in YBCO/Ag Composites

摘要

The improvement of critical current density and mechanical property is essential to the practical application of the superconductive oxides. A solidification technique is developed in this study for the growth of columnar or single Y123 crystal with finely dispersed Y211 and Ag particles through a monotecto-peritectic reaction of L_1(Ba-Cu-Ag-O rich liquid)+Y211->Y123+L_2(Ag rich liquid). The large solidificatin rate and temperature gradient can refine the Ag and Y211 particles. But Ag-free region is widely formed along the crystal growth direction in the central part of the Y123 cell. Since this phenomenon occurs because of the cellular growth, it is necessary to narrow Y123 cell width or to grow Y123 crystal with flat freezing interface. By controlling crystal growth direction using a seed crystal, Y123 columnar or single crystal with uniformly dispersed fine Ag particles are obtained. The behavior of Ag and Y211 particles during the solidification of Y123 crystal is simulated by the peritectic growth model of faceted Y123 crystals.