Percolation analysis of the effect of tape length on the critical current density of 123 coated conductors

Although the RE123 coated conductors substantially consist of highly bi-axially aligned polycrystalline RE123 superconductors, the supercurrent must flow through grain boundaries with some angles of misorientation. To investigate the effects of tape length and number of grains in width on the critical current density (J(c)), percolation analysis was performed considering the J(c) reduction due to misorientation at grain boundaries. The calculation results suggested that the normalized critical current density increased as increasing the number of grains in width and decreased as increasing the tape length. The degree of J(c) reduction as increasing the tape length became smaller as increasing the number of grains in width. The calculation results showed that the J(c) value of 1 km tape conductor with misorientation full width half maximum (FWHM) = 9degrees was possibly kept more than 44% of the intragrain J(c) when the grain number in width was more than 100 with the grain size of 100 mum. The tendency of the calculation results of length and FWHM dependence on J(c) agreed well with the experimentally obtained length dependence on J(c) values of ion-beam assisted deposition conductors. (C) 2001 Elsevier Science B.V. All rights reserved.