Local dissipation and spatial homogeniety in YBCO coated conductors deposited on clad-type textured substrate
MATSEKH Arkadiy, 木須 隆暢, 井上 昌睦 （九大）； 本田 貴裕, 大松 一也 （住友電工）
Abstract:Tape architecture utilizing textured Ni-alloy substrate is one of the most promising methods to realize low cost and high performance coated conductors. Recently developed clad-based YBCO coated conductors poses high critical current density Jc above 2 MA/cm2. In present work we study local flux flow dissipation of such conductors, with different YBCO thickness within 100 to 800 nm range. The purpose of this study is to clarify the current limiting mechanism in the present process.
Films were patterned to 500 to 500 micrometer bridges to obtain multiple grains within the film whose size is several tens micrometers. In order to investigate local flux flow dissipation, we applied low temperature laser scanning microscope (LTLSM). Bias current dependent LTLSM images visualize how local flux flow dissipation gradually appears in the bridge with increasing bias current. Since it first occurs in the most dissipative regions, it is possible to locate weakly and strongly linked grains. Thus, from such current dependent series of images we can find variation of local critical current density.
Grain structure (i.e. grain tilting and grain boundaries) has been visualized by the laser-induced thermoelectric effect (LITE) imaging at room temperature. A good correlation between LTLSM and LITE images was obtained, which showed that some poorly connected grains cannot carry current, acting as blocking obstacles, which are to be studied by microstructural analysis.
This work was supported in part by