Gd–Ba–Cu–O bulk superconductors fabricated by a seeded infiltration growth technique under reduced oxygen partial pressure
Gd–Ba–Cu–O bulk superconductors fabricated by a seeded infiltration growth technique under reduced oxygen partial pressure
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DOI：
10.1088/0953-2048/19/6/038
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发表时间：
2006-06
影响因子：
3.6
通讯作者：
K. Iida;N. H. Babu;Y. Shi;D. Cardwell;M. Murakami
中科院分区：
文献类型：
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作者：
K. Iida;N. H. Babu;Y. Shi;D. Cardwell;M. Murakami
在室温下，采用掺MgO的Nd-Ba-Cu-O（MgO-NdBCO）籽晶，在1%O2 +N2气氛下，采用籽晶渗透生长（SIG）技术生长了单晶粒Gd-Ba-Cu-O（GdBCO）超导体。然而，在空气中制造的MgO-NdBCO晶种在理论上相同的热处理条件下的部分熔化限制了这种大块GdBCO单晶粒工艺的可靠性。观察到的晶种分解归因于MgO掺杂的Nd 1 + xBa 2 − xCu 3 Oy固溶体（MgO掺杂的Nd-123 ss，其中ss表示固溶体）化合物的周晶温度Tp对熔融过程中的氧分压和固溶体水平（x）的依赖性。在p（O2）= 1.00 atm下，MgO掺杂Nd-123 ss（x = 0 ~ 0.5）的高温分解温度为1120 °C。另一方面，在p（O2）= 0.21和0.01大气压的氧分压下，观察到Tp作为固溶体水平的函数线性降低。基于这些结果，MgO掺杂的NdBCO籽晶应在降低的氧分压下生长，以获得稳定的MgO掺杂的NdBCO籽晶，其适用于大晶粒（RE）BCO块体超导体（其中RE是稀土元素）的冷籽晶工艺。
Single-grain Gd–Ba–Cu–O (GdBCO) bulk superconductors have been grown by a seeded infiltration and growth (SIG) technique under a 1% O2+N2 atmosphere using a generic MgO-doped Nd–Ba–Cu–O (MgO–NdBCO) seed placed on the sample surface at room temperature (the so-called the cold-seeding method). Partial melting of the MgO–NdBCO seeds fabricated in air under notionally identical thermal processing conditions, however, limited the reliability of this bulk GdBCO single-grain process. The observed seed decomposition is attributed to the dependence of the peritectic temperature Tp of MgO-doped Nd1+xBa2−xCu3Oy solid solution (MgO-doped Nd-123ss, where ss indicates solid solution) compounds on both oxygen partial pressure during the melt process and the level of solid solution (x). The peritectic decomposition temperature of MgO-doped Nd-123ss, with x ranging from 0 to 0.5 under p(O2) = 1.00 atm, was observed to remain constant at 1120 °C. Tp was observed to decrease linearly as a function of solid solution level, on the other hand, under oxygen partial pressures of both p(O2) = 0.21 and 0.01 atm. Based on these results, MgO-doped NdBCO seed crystals should be grown under reduced oxygen partial pressure in order to obtain a stable MgO-doped NdBCO seed crystal suitable for cold-seeding processes of large-grain (RE)BCO bulk superconductors (where RE is a rare earth element).