Superconducting cluster in YBa2Cu3O7-x ceramic

The method of point laser heating of a sample is used to perform experiment al investigations of the electrical conductivity of YBa2Cu3O7 - x ceramic i n the vicinity of its critical state. It is found that, in the vicinity of transition to the superconducting state, the electrical conductivity of the ceramic exhibits a clusterlike behavior substantially nonuniform over the sample cross section. The topology of a superconducting cluster is investig ated, as well as its spatial localization in the sample. A model of the for mation of a superconducting cluster in a ceramic superconductor is suggeste d. (C) 2000 MAIK "Nauka/Interperiodica".