准单畴YBCO块材当中磁悬浮力不均匀性研究

顶部籽晶熔融织构准单畴Y1B2C3O7-δ中磁悬浮力密度与籽晶位置的关系进行了深入研究.经研究发现在液氮温度下磁悬浮力密度大小随位置变化,在离顶部籽晶3 mm的地方达到最大值,换句话说就是在第二块薄片中具有最大磁悬浮力密度.这种现象可以用晶体生长和吸氧的过程的相互作用来解释.我们提出一个模型,在这个模型中Y211粒子的分布导致的小孔微结构降低了有效感应电流环的大小,从而相当于降低了单畴的有效尺寸,导致磁悬浮力的大小.从研究中发现纵向微裂纹对磁悬浮力的影响最为明显.这个结果对于顶部籽晶熔融织构准单畴的基础研究和制造有很大的意义.

THE INHOMOGENEITY OF LEVITATION FORCE IN SINGLE DOMAIN YBCO BULK

The pellet homogeneity of levitation force vs. the position in comparison to the seed or to the top surface has been studied in the entire volume of a single domain Y1 B2C3O7- δ bulk sample processed by the Top-seeded Melt texturing growth (TSMTG). It is found that the levitation force increase and peak at a depth of 3 mm from the top of the sample at liquid nitrogen temperature. In other words, the second disk has the largest levitation force density. The phenomenon can be interpreted by the interaction between the microcracks or pores produced by crystal growth and the oxygenation. We propose a model in which Y211 particles distribution leading to microcracks and pores, therefore reduce the effective induced shielding current loops (ISCL) and increases the perimeters of ISCL, and thus this is corresponding to a decrease in the grain size, and thus result in greatly reduce levitation force in the bottom of the bulk.From the research, we know that the portrait microcracks of the YBCO bulk are also an important effect on the levitation properties. The result is very attractive and useful for TSMTG YBCO bulk fundamental studies and fabrication.