Properties of recent IBAD–MOCVD coated conductors relevant to their high field, low temperature magnet use

Abstract

BaZrO3 (BZO) nanorods are now incorporated into production IBAD-MOCVD coated\nconductors. Here we compare several examples of both BZO-free and\nBZO-containing coated conductors using critical current (Ic) characterizations\nat 4.2 K over their full angular range up to fields of 31 T. We find that BZO\nnanorods do not produce any c-axis distortion of the critical current density\nJc(theta) curve at 4.2 K at any field, but also that pinning is nevertheless\nstrongly enhanced compared to the non-BZO conductors. We also find that the\ntendency of the ab-plane Jc(theta) peak to become cusp-like is moderated by BZO\nand we define a new figure of merit that may be helpful for magnet design - the\nOADI (Off-Axis Double Ic), which clearly shows that BZO broadens the ab-plane\npeak and thus raises Jc 5-30{\\deg} away from the tape plane, where the most\ncritical approach to Ic occurs in many coil designs. We describe some\nexperimental procedures that may make critical current Ic tests of these very\nhigh current tapes more tractable at 4.2 K, where Ic exceeds 1000 A even for 4\nmm wide tape with only 1 micron thickness of superconductor. A positive\nconclusion is that BZO is very beneficial for the Jc characteristics at 4.2 K,\njust as it is at higher temperatures, where the correlated c-axis pinning\neffects of the nanorods are much more obvious.\n