权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Controlling the Critical Current Density under Magnetic Field of Melt Processed Bulk High Temperature Superconductors

熔融加工块体高温超导体磁场下临界电流密度的控制

基本信息

批准号：
14350006
负责人：
IKUTA Hiroshi
金额：
$ 7.3万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

The change of the critical current density (J_c) as well as the trapped field of melt-processed bulk superconductors brought about by an element substitution, oxygen annealing, changing the composition of the starting materials and so on were systematically studied. First, we optimized the starting composition of the Dy-system. Then, CeO_2 was added, which decreased the loss of the melt during the processing, resulting in a more than 10% increase in the trapped field. The addition of ZnO to this composition increased J_c between 0 and 3 T, and the trapped field increased for 20%. The optimum content of ZnO for increasing J_c and the trapped field was determined to be about 0.025 wt.% independent of the sample size and regardless whether CeO_2 is added or not. When ZnO was added to the Sm-system, the trapped field increased by a factor of 1.5. It was elucidated that the increase in J_c with Zn doping is particularly large in the region beneath the seed crystal where the Sm211 phase is d … More eficient, and this brought about the increase of the trapped field. We have also succeeded for the first time the preparation of single-domain bulk samples of the ternary Nd-Eu-Gd system with a diameter equal to or larger than 30 mm. The trapped field of these samples was larger when the ratio of Gd in the 211 phase of the starting materials was smaller, but the material strength increased when the content of Gd was large. Consequently, the magnetic flux density that the sample could trap without being cracked at low temperature increased. Similarly, the trapped field at the liquid nitrogen temperature of the ternary Sm-Eu-Gd system was large when the content of Gd of the 211 phase was 50%. The diffusivity of oxygen in a melt-processed superconductor was found to be between single-and poly-crystalline samples, and decreases when Ag is added because the microstructure is denser. It was important to perform the oxygen annealing at low temperature for the Sm-system in order to obtain a sample with large J_c and trapped field. However, the diffusivity decreases at lower temperature, and therefore, we studied the effect of high pressure oxygen annealing under 10 atm. Based on that result, we proposed a two-step annealing process, and confirmed its effectiveness. We also prepared samples of the Sm-system with adding Y_2Ba_4CuZrO_y, which was reported to have a small size in melt-processed superconductors, and found that the addition of this material compensates the Sm211 phase that is deficient under the seed crystal, and the trapped field increased with a very small content of about 1mol%. Less

系统地研究了元素替代、氧退火、改变原料组成等因素对熔融处理大块超导体的临界电流密度(J_C)和俘获场的影响。首先，我们优化了Dy-系统的起始组成。然后加入CeO2，减少了熔体在加工过程中的损失，使俘获场增加了10%以上。氧化锌的加入使J_c在0~3T范围内增加，俘获场强增加20%。确定了提高J_c和陷阱场的最佳氧化锌含量为0.025%左右，与样品大小无关，也与CeO_2的加入与否无关。当在Sm-体系中加入氧化锌时，俘获场增加了1.5倍。结果表明，在晶种下的Sm211相为d…的区域，掺锌后J_c的增加幅度特别大效率更高，这就带来了俘获场的增加。我们还首次成功地制备了直径大于或等于30 mm的ND-Eu-Gd三元系单畴块体样品。当Gd在起始材料的211相中的比例较小时，这些样品的俘获场较大，但当Gd含量较大时，材料的强度增加。因此，样品在低温下可以捕获而不破裂的磁通密度增加。同样，当211相中Gd含量为50%时，Sm-Eu-Gd三元系在液氮温度下的俘获场较大。氧在熔融处理超导体中的扩散系数介于单晶和多晶样品之间，随着Ag的加入，氧的扩散系数减小，这是因为其微观结构更致密。为了获得具有较大J_c和陷阱场的样品，对Sm-系统进行低温氧退火是非常重要的。然而，在较低的温度下，扩散系数降低，因此，我们研究了在10个大气压下的高压氧退火的效果。在此基础上，提出了两步退火法，并对其有效性进行了验证。我们还制备了添加Y_2Ba4CuZrO_y的Sm系统样品，这种材料在熔融处理的超导体中具有很小的尺寸，发现这种材料的加入补偿了种子晶体下缺乏的SM211相，并且俘获场增加了很小的含量，约为1mol%。较少