INTERGRANULAR PROPERTIES OF (Y1-x-yZrxCay)Ba2Cu3O7-δ COMPOUNDS

The intergranular properties of (Y1-x-yZrxCay)Ba2Cu3O7-δ ceramics were studies by using temperature-dependent ac susceptibility measurements at zero dc magnetic field. The intergranular critical current density was determined from ac susceptibility data by varying the field amplitude Hac. From the imaginary part of the complex susceptibility, χ″(T), we have determined the temperature dependence of the critical current density by using the Bean's model. The ac field dependencies of the intergrain χ″-peak temperatures Tp are linear and agree with Müller critical state model. The results were analyzed in terms of superconductor-insulator-superconductor (SIS)-and superconductor-normal-superconductor (SNS)-type models for granular superconductors.