The identification of grain boundary networks of distinct critical current density in YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-x</inf> coated conductors

Evidence for the existence of grain boundary (GB) networks with different critical current densities has been obtained in YBa2Cu 3]O7-x coated conductor tapes, through distinct magnetic responses in AC susceptibility measurements. Percolating currents through GB networks of different quality may be distinguished by the appearance of modified dissipation contributions in the imaginary component of the AC susceptibility. The application of the Bean critical-state model to the AC susceptibility response of finite size samples has allowed us to properly quantify these critical current densities. AC susceptibility appears as a unique direct measurement of the temperature-dependent intergrain critical current densities with additional information about the current networks, which cannot be reached by transport measurements.