典型颗粒超导体YBa＿2Cu＿3O＿7／V＿2O＿5中临界电流随温度变化的特性

CHARACTERISTICS OF TEMPERATURE DEPENDENCE OF CRITICAL CURRENT IN TYPICAL GRANULAR SYSTEM YBa_2Cu_3O_7/V_2O_5

通过制备（ＹＢａ＿２Ｃｕ＿３Ｏ＿７）＿（１－ｘ）（Ｖ＿２Ｏ＿５）＿ｘ（０≤ｘ≤０．１５）复合材料，获得了一系列典型的弱连接的颗粒超导体，其中以ｄＲ／ｄＴ－Ｔ关系中呈现出双峰转变为主要特征。第一峰代表晶粒的超导转变，第二峰代表颗粒系统超导长程序的形成。对于具有双峰转变的样品，其临界电流密度一致地符合ｉ＿ｃ～（１－ｔ）￣ｎ，ｎ＝１．６．这一行为与三维Ｊｏｓｅｐｈｓｏｎ结网络系统的渗流行为相一致；对于不具有双峰转变的系统，临界电流密度随温度的变化尽管也可以用ｊ＿ｃ～（１－ｔ）￣ｎ描述，但是幂指数ｎ明显地大于１．６，且随样品的不同而离散地分布。本文还对产生这种离散的原因进行探索和分析。

By synthesising the(YBa_2Cu_3O_7)_(1-x) (V_2O_5)_x(0<X<0.15)complex materials,thegranular superconductors with a wide range of coupling strength have been obtained.Two peaks are observed in dR/dT-T curve for samples of sufficient weak couplingbetween the grains,in which the second peak represents the formation of the supe-rconducting long-range ordering of the granular system. Moreover,in this kind ofsamples shown the two-peak transition,the critical current all obey the law:J_c∞(1-t)￣n with n=1.6 without exception,this can be interpreted with the percolationof a three-dimensional network Josephson-junction system. However,for those withoutthe two-peak transition,the n value is larger than 1.6,and distributes within a widerange. The cause for the distribution of n value are also considered and discussed.