中文摘要：

为了有效地抑制Gd BCO超导块材在生长过程中出现的Gd/Ba替换现象,在前期工作的基础上,本文采用顶部籽晶熔渗生长工艺,通过在固相先驱粉中添加不同含量的Ba O粒子成功地制备出了一系列高性能的单畴Gd BCO超导块材,并且对样品的微观形貌以及临界电流密度进行了研究和分析.结果表明,随着BaO掺杂量的增加,样品中的Gd1＋xBa2-xCu3O7-δ固溶体（Gd123ss）相呈现出减少的趋势,并生成了纳米量级的Gd123ss,这对GdBCO超导样品中存在的Gd/Ba替换起到了很好的抑制作用,使得样品中的GdBa2Cu3O7-δ（Gd123）超导相有所增加;同时当样品中BaO的添加量在2 wt%—4 wt%之间时,样品的临界电流密度在一定程度上得到了有效提高.

英文摘要：

In order to inhibit the Gd/Ba substitution in the growth process effectively, a series of single domain GdBCO bulk superconductors with different ratios of Ba O additions in the solid phase pellet is successfully fabricated by the modified top seeded infiltration growth technique on the basis of previous research. In the present work, the macroscopic feature,microstructure and critical current density（J_c） of the single domain GdBCO bulk superconductor are investigated in detail. From the top view of the surface of the single domain GdBCO bulk superconductor, all of the samples exhibit clearly the fourfold growth sector boundaries on their top surfaces, and spontaneous satellite grains are observed in none of these samples. It can be seen that the different ratio of Ba O addition（from 1 wt% to 4 wt%） cannot affect the growth morphology of the single domain GdBCO bulk superconductor. At the same time, for observations of the microstructure, the small test specimens of dimensions about 2 mm × 2 mm × 2 mm are cut from the top surface of the singe domain GdBCO bulk superconductors with different Ba O doping ratios and at a distance 5 mm away from the seed, then microstructure analysis is performed in the cleavage phane of the test specimen by using scanning electron microscope. For the sample with 1 wt% Ba O doping, the derivative phase of GdBCO（Gd123ss） is found in the Gd123 superconducting matrix. To detect the atomic ratio of the Gd123 ss, energy dispersive X-ray spectrometry measurement is carried out on the samples. It is shown that the atomic ratio of the Gd123 ss phase is Gd ： Ba ： Cu = 1.566 ： 1.459 ： 3,which proves successfully that the Gd123 ss is a kind of phase with lack of barium. With the increase of Ba O doping, the phenomenon of lack of barium is effectively controlled and, the nano Gd123 ss phase is generated as the flux pinning centre which can be used to improve the superconducting properties in the growth process of GdBCO bulk superconductor.This results can be concluded that