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A basic study on high-temperature superconductor cables available in liquid nitrogen

液氮中高温超导电缆的基础研究

基本信息

批准号：
12650265
负责人：
SUZUKI Mitsumasa
金额：
$ 2.3万
依托单位：
Utsunomiya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

A lot of high-temperature superconductors have layer structure and their critical current density is depressed under magnetic fields applied parallel to crystallographic c-axis. This anisotropy is a crucial factor for designing superconducting cables operating in magnetic fields, and limits the range of the practical use of high-temperature superconductors. In this study, superconducting characters of Yba_2Cu_3O_<7δ>(YBCO) have been investigated from the practical viewpoints of electric power cables of YBCO. YBCO films used in this study have been prepared by sputtering. Optimum deposition conditions for producing YBCO films on MgO (100) have been made clear. The growth of YBCO phase is dominated by deposition temperature, one of deposition conditions, and c-axis oriented YBCO films indicative of high critical temperature T_c and high critical current density J_c grow around 900℃. 45°-rotated YBCO grains appear in films with increasing deposition temperature above 900℃ and J_c of films is appreciably reduced. Substrate material and surface treatments of substrates give effects the growth of YBCO grains. On SrTiO_3 (100) substrates and MgO(100) substrates surface-treated by acid etching, well-regularized spiral growth of YBCO is seen. These films show high-J_c values in excess of 3×10^6 A/cm^2.In conclusions, c-axis oriented films with highly bi-axially aligned structure provides high-J_c character. Precise control of deposition temperature, lattice-matching substrates with YBCO and surface treatments of substrates are required in preparing high-J_c YBCO films.

许多高温超导体具有层状结构，在平行于晶体c轴的磁场作用下，其临界电流密度被压低。这种各向异性是设计工作在磁场中的超导电缆的关键因素，并限制了高温超导体的实际应用范围。本研究从YBa2Cu3O7δ(YBCO)电力电缆的实用角度出发，研究了YBa2Cu3O7(YBCO)的超导特性。本文所用的YBCO薄膜是用溅射方法制备的。明确了在MgO(100)衬底上制备YBCO薄膜的最佳沉积条件。沉积温度是影响薄膜生长的主要因素之一，具有高临界温度T_c和高临界电流密度J_c的c轴取向生长的YBCO薄膜在900℃左右生长。在900℃以上，随着沉积温度的升高，薄膜中出现了45°旋转的YBCO颗粒，薄膜的J_c明显降低。衬底材料和衬底表面处理对YBCO颗粒的生长有一定的影响。在经酸蚀处理的SrTiO3(100)衬底和MgO(100)衬底上，观察到规整的YBCO螺旋生长。这些薄膜具有高J_c值，超过3×10~(-6)A/cm~2。总之，具有高度双向取向结构的c轴取向薄膜具有高J_c特性。在制备高J_c YBCO薄膜时，需要精确控制沉积温度、衬底与YBCO的晶格匹配以及衬底的表面处理。