Visualizing Transport Properties in IBAD Based YBCO Coated Conductors by Multiple Analysis Techniques

摘要

Current transport properties in ${rm Y}_{1}{rm Ba}_{2}{rm Cu}_{3}{rm O}_{7-delta}$ (YBCO) coated conductors obtained by pulsed laser deposition process on a ${rm CeO}_{2}$ capped ${rm Gd}_{2}{rm Zr}_{2}{rm O}_{7}hbox{–}{rm IBAD}$ template have been studied by spatially resolved measurements. We utilized low temperature scanning laser microscopy along with laser induced Seebeck effect imaging and scanning SQUID microscopy that allow us to visualize 1) distributed flux flow dissipation, 2) current blocking obstacles and 3) local current flow, respectively. Combination of those measurements leads deep insights into current limiting mechanism in the coated conductor. Our results show that non-uniform current flow due to spatially distributed obstacles is responsible for the dissipation, whereas grain connectivity in each YBCO grains is not the limiting factor. Typical period of those obstacles is several tens $mu{rm m}$ to hundreds $mu{rm m}$. Detailed correlation between local current flow and dissipation has been observed. Present methods have great potential as tools for basic understanding of current limiting mechanisms in the coated conductors.