INTERGRANULAR AND INTRAGRANULAR EFFECTS IN MICROWAVE-ABSORPTION OF (BI, PB)2SR2CA2CU3OY

Detailed low DC-field microwave absorption (LFMWA) and AC-susceptibility measurements were performed over a wide temperature range for high-quality bulk and fine powder samples of the (Bi,Pb)2Sr2Ca2Cu3Oy compound. The features observed in fine powders are quite different from those observed in bulk samples. This allows one to make a separation of intragranular from intergranular effects. We find an intragranular critical current density of order 10(4) A/cm2, which is probably the intrinsic critical current density in the c-direction of the Bi-2223 compound due to the Josephson junctions formed by a repeat spacing of nearly insulating and highly conducting atomic planes along the c-direction of the crystal structure. The corresponding penetration depth lambda-c for fields parallel to the a,b-planes is about 35-mu-m. Furthermore, we can detect the presence of < 3% Bi-2212 defect layers in the Bi-2223 crystallites.