Preparation of Large size Bi-based Superconducting Single Crystals with High Critical Current Density

高临界电流密度大尺寸铋基超导单晶的制备

基本信息

批准号：
14550019
负责人：
IMAO Hiroya
金额：
$ 1.79万
依托单位：
Matsue National College of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
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

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550019/
关键词：
Bi-based Superconductor Single Crystal Critical Current Density Bi系超電導体

项目摘要

In order to apply Bi_2Sr_2Ca_<m-1>Cu_mO_<2m+4+δ>(Bi-based) superconductor into the field of power electronics, it is important to prepare it with a high critical current density (Jc). In this study, we prepared the Bi-based superconducting single crystals by a self-flux method and investigated the effects of the growth condition on the Jc, Tc, crystal sizes and weights of crystals.We grew the Bi_2Sr_2CaCu_2O_x (Bi-2212) single crystals by a self-flux method, where the Bi-2212 single crystals prepared at the first growth were used as a starting material in the second growth. This is called re-growth method. The size of the crystals prepared in the second growth was larger than that prepared in the first growth. Therefore, to use the Bi-2212 single crystals as starting materials is effective for obtaining large Bi-2212 single crystals. From the results of XRD pattern and of R-T characteristics, we found that the single crystals prepared by the re-growth method had a Bi-2212 superconductor and did not contain any impurity phases.Large volumes of the single crystals were obtained by using the large crucibles. When smaller crucibles were used, the 30% volume of the starting materials became the single crystals. The rate of single crystals to the starting materials prepared by the large crucibles were larger than those prepared by the small crucibles. The weight of the single crystals prepared at the cooling rate of 1℃/h was about 130g. The results indicate that the single crystal corresponds to the 65% weight of the starting materials. Therefore, the large crucibles are useful for effective production of Bi-2212 single crystals.However, the measurement of critical current is difficult because of the instability of the electrodes formed on the surfaces of single crystals. We need the research of the electrode formation on to the single crystal surfaces to the step of the growth of the high Jc single crystals.

为了将Bi_2Sr_2Ca_<m-1>Cu_mO_<2m+4+δ>（Bi基）超导体应用于电力电子领域，制备具有高临界电流密度（Jc）的超导体非常重要。我们采用自熔法制备了Bi基超导单晶，并研究了生长条件对Jc、Tc、晶体尺寸和晶体重量的影响。采用自熔法制备Bi_2Sr_2CaCu_2O_x（Bi-2212）单晶，其中将第一次生长制备的Bi-2212单晶用作第二次生长的起始材料，这称为再生长法。第二次生长中制备的晶体比第一次生长中制备的晶体更大，因此，使用Bi-2212单晶作为起始材料对于获得大的Bi-2212单晶是有效的。从X射线衍射图谱和R-T特性结果来看，再生长法制备的单晶具有Bi-2212超导体，且不含任何杂质相。通过使用该方法获得了大体积的单晶。当使用较小的坩埚时，30％体积的原料成为单晶，大坩埚制备的原料中单晶的比例更大。与小坩埚制备的单晶相比，在1℃/h的冷却速率下制备的单晶的重量约为130g。结果表明，该单晶相当于起始材料的65％。坩埚对于Bi-2212单晶的有效生产很有用。然而，由于单晶表面形成的电极不稳定，临界电流的测量很困难，我们需要对电极形成进行研究。单晶表面到高Jc单晶生长的步骤。