Alternating magnetic field losses in high-Tc superconducting multifilament tapes with a mixed matrix of Ag and BaZrO₃

Alternating magnetic field losses for the new (Bi, Pb)2Sr2Ca2Cu3O10 multifilament tapes with a mixed Ag–BaZrO3 matrix for coupling loss reduction have been measured at 77 K and at frequencies up to 100 Hz. Due to the presence of oxide barriers around the filaments, the effective transverse electrical resistivity in the matrix is increased by a factor of eight, with a corresponding modification of the frequency dependence of the coupling losses. This result is a very promising step in the development of low loss high-Tc superconductors for 50 Hz applications. For larger ΔB values, it seems feasible to reduce the coupling losses at 50 Hz to a tolerable level by both, applying high-resistive barriers and changing the conductor dimensions, away from the extremely flat tape geometry. A saturation loss criterion is derived for twisted flat multifilament tapes