【摘要】 顶部籽晶技术与熔融织构生长工艺的结合已经被证明是制备单一晶体取向的YBaCuO单畴超导体的成功方法.由于YBaCuO晶体的生长速度慢,使大尺寸单畴超导快的制备受到限制.采用多籽晶的方法可以减少生长大块材料的时间,但多籽晶诱导生长的大晶粒的边界通常是弱耦合的,材料的磁浮力和冻结磁场性能明显低于单籽晶生长的材料.本研究在采用多籽晶法制备YBCuO超导块时,通过在先驱物坯料的顶部增加成分梯度过渡层的方法成功地生长出单畴结构的超导材料.冻结磁通的分布为单峰状,证实材料为单畴结构,其磁浮力也达到单籽晶样品的水平.这些结果表明成分梯度层和多籽晶结合的工艺可以改善多籽晶生长样品的晶界耦合,是生长大尺寸单畴超导材料的一种可行方法.更多还原

【Abstract】 Although large single domain YBCO superconducting bulk can be produced by using the top-seeded melt process, it takes a quite long period for the grain growth because of an extremely low growth rate of YBCO-123 phase. In order to overcome such a problem, the multi-seeded melt growth (MSMG) technique has been developed. However, in the MSMG-processed YBCO samples, grain boundaries formed between two adjacent grains often is weak links. In this paper, we report a new method prepared single domain YBCO bulk by using modified MSMG. The precursor is composed of layers (Layer-A and layer-B) with composition gradient. The composition of layer-A is (Y_ 1-x Gd_x)_ 1.8 Ba_ 2.4 Cu_ 3.4 O_y (x0.1, 0.2) and layer-B is Y_ 1.8 Ba_ 2.4 Cu_ 3.4 O_y. The peritectic temperatures of layer-A is higher than layer-B. Four SBCO seeds with same size and orientations were placed on the layer-A before the melt process. The trapped field distributions for the bulk superconductors prepared by this modified MSMG method showed a single peak, simulate to the top-seeded melt process using single seed, indicating that the sample had single domain structure.更多还原