SUPERCONDUCTIVITY AND ELECTRICAL-TRANSPORT IN YBA2CU3O7-DELTA-PRBA2SNO5.5, PERCOLATION SYSTEM

Pere elation behaviour of the normal state resistivity and superconduc tivity of YBa2Cu3O7-deltaPrBa2SnO5.5 composites have been studied by X -ray diffraction and temperature-resistivity measurements. No detectab le chemical reactivity was observed between YBa2Cu3O7-delta and a cera mic insulator PrBa2SnO5.5 even when the two materials were mixed thoro ughly and sintered at 1020 degrees C. The normal state percolation thr eshold is 21 vol% of YBa2Cu3O7-delta and the superconducting percolati on threshold is 30 vol% of YBa2Cu3O7-delta in thc composite. The value s obtained for the critical exponents describing the normal state tran sport. behaviour of the sq stem matched with theoretically expected va lues for an ideal conductor-insulator system. The implications are dis cussed.