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

Study on High Temperature Superconductors -Properties and Formation Techniques of Bulk and Thin Film-

高温超导体研究-块体薄膜和薄膜的性能及形成技术-

基本信息

批准号：
02045043
负责人：
OKUDA Takayoshi
金额：
$ 3.46万
依托单位：
Daido Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

The Kosterlitz-Thouless theory for the electrical dissipation in the high temperature superconductors predicts scaling of the current voltage characteristics above th phase transition temperature (Tc) but not below. We give an expression for universal scaling curve which provides an excellent fit to the data for epitaxial YBa_2Cu_3O_7 thin films taken in zero applied magnetic field.Unusual low magnetic field behaviours have been observed in samples of the YBCO composite sinters which contain an appreciable proportion of the insulating 211 phase. These composite materials exhibit a phase-transition in their electrical characteristics at a temperature Tp which is less than Tc the mean field superconducting transition temperature. As an applied magnetic field is increased from zero at temperatures below Tc, the electrical dissipation exhibits a minimum at about 5 Gauss, before it increases in the manner usually found in the superconducting ceramics. At temperatures below the phase transit … More ion temperature Tp, a further sharp minimum in the dissipation develops at zero field.We have investigated features in the current voltage (I-V) characteristics of YBa_2Cu_3O_7:Y_2BaCuO_5 composite sinters which indicate the occurrence of a second-order phase transition. For each sinter composition similar families of characteristics are found for a wide range of magnetic fields. the relation between V and I is seen to be of the form V=f(I, xi (B,T)) where simple parameter xi contains all of the field and temperature dependence. The locus of points in the B,T plane for which xi (B,T) is a constant have been examined, and a low field and a high field regime have been identified. Samples of different composition show families of I-V characteristics which scale onto one another in a simple way, hence we are let to suppose the V = f(I, xi (B,T,p)) where p is the dilution fraction. Data taken at temperatures below transition, with exponents which are independent of magnetic field and composition. Above the transition, however, the behavior is more complex.Growth condition of the high temperature superconducting whiskers has been investigated in the BSCCO(2212) system. Growth rate of the whisker depends strongly on Bi content in the melt-quenched glass substance and an annealing temperature.Superconducting fine powder has been prepared by spray pyrolysis. Hydrogen peroxide which is added in the nitrid acid solvent is found to suppress the impurity formation in the powder. A higher abundance (90%) of Low-Tc phase was achieved. Less

高温超导体的Kosterlitz-Schloss电耗散理论预言，在相变温度以上，电流电压特性成比例变化，而在相变温度以下则不成比例变化。本文给出了一个普适标度曲线表达式，它与外延YBa_2Cu_3O_7薄膜在零磁场下的实验数据有很好的拟合，在含有相当比例的绝缘211相的YBCO复合烧结体样品中观察到了异常的低磁场行为。这些复合材料在低于平均场超导转变温度Tc的温度Tp下表现出其电特性的相变。当所施加的磁场在低于Tc的温度下从零开始增加时，在以超导陶瓷中通常发现的方式增加之前，电耗散在约5高斯处表现出最小值。在低于相变温度时， ...更多信息本文研究了YBa_2Cu_3O_7：Y_2BaCuO_5复合烧结体的伏安特性，发现其存在二级相变。对于每个烧结组合物的特性相似的家庭被发现在很宽的磁场范围。可以看出V和I之间的关系具有V=f（I，xi（B，T））的形式，其中简单参数xi包含所有的场和温度依赖性。在B，T平面上的点的轨迹，其中xi（B，T）是一个常数已被检查，并已确定了一个低场和一个高场制度。不同成分的样品显示出I-V特性族，它们以简单的方式彼此成比例，因此我们假设V = f（I，xi（B，T，p）），其中p是稀释分数。在低于转变温度下取得的数据，其指数与磁场和成分无关。在BSCCO（2212）系统中研究了高温超导晶须的生长条件。晶须的生长速度与玻璃熔体中Bi的含量和退火温度密切相关。发现在硝酸溶剂中加入过氧化氢可以抑制粉末中杂质的形成。实现了更高丰度（90%）的低Tc相。少