Ag掺杂SmBCO熔融织构单畴生长工艺研究  

STUDY ON THE GROWTH OF SmBCO/Ag SINGLE-GRAIN BULK

作　　者：吴兴达[1] 徐克西[1] 泮朋军[1] 

机构地区：[1]上海大学物理系,上海200444

出　　处：《低温物理学报》2009年第2期107-112,共6页Low Temperature Physical Letters

基　　金：上海市重点科研基金(项目编号:S30105)资助的课题~~

摘　　要：通过Ag掺杂降低Sm123/Sm211体系熔点,利用Nd123冷籽晶技术成功制备出具有理想织构的SmBCO/Ag单畴块材.研究了SmBCO/Ag单畴的生长过程,结果发现,相比于未掺杂坯体,掺入Ag后的SmBCO坯体生长速率下降,在所考察的慢冷温区里,生长速率呈不断减小趋势,最终因自发成核而无法继续生长.实验还发现,SmBCO/Ag单畴生长温度窗口随Ag掺量增加向低温区平移.对样品剖面的观察发现,在最高熔化温度保温阶段大量气体未能排出SmBCO/Ag坯体,这些气体在单畴慢冷生长过程中不断向外侧迁移、合并形成宏观可见的孔洞.在单畴生长过程中,这些位于生长前沿的高密度气孔,一定程度上影响了液相和Sm3+离子向生长前沿的供应,是单畴生长速率较低的可能原因.微结构分析表明熔融生长过程中Sm211粒子发生二次晶粒长大现象,长大后的Sm211粒子提供Sm3+离子的能力减弱,导致慢冷生长后期阶段生长速率呈下降趋势.The melting point of Sm123/Sm211 system is decreased by Ag addition, and very well textured SmBCO/Ag mono-domain bulks have been successfully prepared using Nd123 cold-seeding technique. Study on single-domain growth of SmBCO/Ag bulk has been carried out. It has been shown that the growth rate of SmBCO bulk is reduced by Ag addition. Furthermore, single-domain growth exhibits a sup- pressed tendency within the slow-cooling temperature window considered and then is stopped by the oc-currence of random nucleation. Several samples containing different amounts of Ag have been grown with-in the same slow-cooling temperature window. It has been found that the temperature window within which steady-state growth of SmBCO/Ag can be achieved moves towards lower temperature zone when the content of Ag is increased. The transversal slides of the samples show that large amount of entrapped gas did not escape from the sample during the dwell time at the maximum superheating temperature, and a large density of small pores was formed. During the slow-cooling process, these pores moved towards the edges of the samples, coalesced with each other and formed large pores several millimeters in size, which finally were released from the sample. However, the diffusion of Sm^3＋ ion and liquid phase which are necessary for the growth of single-domain is hindered and then the growth rate was reduced. The SEM a- nalysis reveals that the coarsening of Sm211 precipitates has occurred during the growth of mono-domain. Large Sm211 cause decreased ability to supply samarium for the growth of Sm123 crystal, resulting in a gradual decrease in the growth rate.

关 键 词：Ni80Fe20SmBCO AG掺杂 单畴生长 

分 类 号：TB33[一般工业技术—材料科学与工程]