中文摘要：

采用改进后的顶部籽晶熔渗生长（M-TSIG）工艺,通过在固相先驱粉体中掺杂不同含量的BaO来有效地抑制GdBCO样品生长过程中出现的Gd/Ba替换现象,从而成功地制备出了一系列单畴Gd BCO超导块材,并且对样品的宏观形貌、磁悬浮力、捕获磁通密度及临界温度等超导性能进行了研究.结果表明,随着BaO掺杂量的增加,样品的熔化温度（Tm）及包晶反应温度（Tp）均出现逐渐降低的趋势;同时,当样品中BaO的添加量在2wt%—4wt%时,可以在一定的程度上有效提高Gd BCO样品的磁悬浮力、捕获磁通密度及临界温度等超导性能.

英文摘要：

In this work,a series of single domain Gd BCO bulk superconductors with different ratios of Ba O addition in the solid phase pellet,is successfully fabricated to inhibit the Gd/Ba substitution in the growth process by the modified top seeded infiltration growth（M-TSIG） technique.The reaction of the precursor powders,the growth morphology,the magnetic levitation force（F）,the trapped magnetic flux（Btr） and critical temperature（Tc） of the single domain Gd BCO bulk superconductors are investigated in detail.First,the differential thermal analysis is performed on the precursor powders of 10 mg solid phase pellet（containing various amounts of Ba O） and 15 mg liquid phase pellet in order to investigate the melting temperature（Tm） and the peritectic temperature（Tp） of the Gd BCO superconductor system.The results show that the melting point of the precursor powder decreases by nearly 8？C as the Ba O composition increases from0 wt% to 4 wt%,which leads to Tp decreasing with Ba O content increasing.Second,the top view morphologies of the Gd BCO samples are also discussed.All of the samples exhibit clear,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 cannot affect the growth morphology of the single domain Gd BCO bulk superconductor.And thirdly,the levitation force and trapped field of each of the samples are measured under a zero field cooling state at 77 K by the three-dimensional magnetic force and field device.The values of the levitation force for the samples are slightly different for different ratios of Ba O additions.The largest levitation force is 35 N,which is obtained in the sample with 2.5 wt%,and the smallest one is 28 N in the sample with 1 wt% Ba O addition.And also,the trapped field of the sample can be attributed simply to the variation in the pinning strength.It can be obviously seen that these values fluctuate between0.28 T and 0.32 T for the