Dimensionality of YBCO superconductors evaluated by inductive method

The normal-superconductor transition of sintered YBCO samples was monitored by AC susceptibility measurements. Applying a supplementary (square-wave) magnetic field modulation, the in-phase susceptibility signal's envelope pr esents a maximum. The temperature belonging to this maximum coincides with the characteristic zero-resistance temperature (T-c). This coincidence make s it possible for the method to be used not only for the correct determinat ion of T-c but also for the estimation of the fraction of the superconducti ve material to the rest, for a percolation path to start. The similar to0.5 percolation threshold found and the similar to0.05 bond occupation probabi lity among planar clusters confirm that the superconductivity in our granul ar samples is a quasi-two-dimensional case. (C) 2001 Elsevier Science B.V. All rights reserved.