Nonsuperconducting Micron Size Particle asEffective Pinning Centre for Enhanced J_c in High-T_c Superconductors

摘要

Understanding the real mechanism responsible for achieving high transport criticalcurrent density (J_c) in the high temperature (high-T_c) cuprate superconductors has been one of theprimary goal. The only promising way is to tailor the high-Tc cuprate material during preparationstage incorporating suitable non-superconducting particles within superconducting matrix, whichare known to serve as effective pining centers . Incorporation of non-superconducting particle likesilver with dimension down to micron/submicron size in the superconducting matrix is very stableand form a homogenous solid solution matrix, which has got the better stability on aging and foundto be effective in enhancing flux pining in high-Tc superconducting system. In this paper , studieshave been made to investigate and review the effect of non-superconducting micron size Agparticle in to the matrix of RE-Ba-Cu-O ( RE = Sm,Gd & Y ) 123 high –Tc ceramicsuperconducting system . XRD, SEM, magnetization, magnetotransport and microwave induce DCvoltage measurements were carried out to study the effect of Ag into 123- superconducting system.It is observed that controlled addition of Ag into Sm-Ba-Cu-O ( SBCO ) , Gd-Ba-Cu-O ( GBCO )and Y-Ba-Cu-O ( YBCO ) ceramic superconductor do not react with the decomposed phases butremains in the metallic form. This brings about a lowering of the normal-state resistivity . Theincrease of magnetic critical current density (Jmc ) ,transport critical current density ( Jtc ) , and,hence pinning force density ( F_p )with Ag addition into above three systems suggest the creationof an SNS-type proximity junction at the intergranular region and stronger Josephson current pathsbetween the superconducting intergrains. This is attributed to the physical densification andconsequent reduction of the total number of weak links by Ag addition into the above mentionedceramic superconducting system.