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

BaZrO(3) (BZO) nanorods are now incorporated into production IBAD-MOCVD coated conductors. Here we compare several examples of both BZO-free and BZO-containing coated conductors using critical current (I(c)) characterizations at 4.2 K over their full angular range up to fields of 31 T. We find that BZO nanorods do not produce any c-axis distortion of the critical current density J(c)(theta) curve at 4.2 K at any field, but also that pinning is nevertheless strongly enhanced compared to the non-BZO conductors. We also find that the tendency of the ab-plane J(c)(theta) peak to become cusp-like is moderated by BZO and we define a new figure of merit that may be helpful for magnet design-the OADI (off-axis double I(c)), which clearly shows that BZO broadens the ab-plane peak and thus raises J(c) 5 degrees-30 degrees away from the tape plane, where the most critical approach to I(c) occurs in many coil designs. We describe some experimental procedures that may make critical current I(c) tests of these very high current tapes more tractable at 4.2 K, where I(c) exceeds 1000 A even for 4 mm wide tape with only 1 mu m thickness of superconductor. A positive conclusion is that BZO is very beneficial for the J(c) characteristics at 4.2 K, just as it is at higher temperatures, where the correlated c-axis pinning effects of the nanorods are much more obvious.