Critical currents in ceramic high temperature superconductors

YBa_2Cu_3O_x, Bi_2Sr_2Ca_2Cu+3O+x, Bi_2Sr_2CaCu_2O*00x ceramics are considered in the paper aiming at the experimental investigation of transport and magnetic properties of ceramic compounds YBa2Cu_3O_x, Bi_2Sr_2Ca_2Cu_3O_x, Bi_2Sr_2CaCu_2Ox in the superconducting state. As a result the measurement of voltampere characteristics (VAC) by four-contact and contactless methods has been held as well as measurements of magnetization curve lines with the variation of a magnetic field and measurements of a logical magnetic field under low temperatures. The influence of the own magnetic field on the critical current value has been established. The relaxation of transport critical current has been detected and investigated. The calculation of magnetization curve lines in weak fields has been tested. Volt-ampere characteristics in the wide interval of stresses have been measured, the explanation of their S-character has been suggested. The results obtained make it possible to establish the laws of the behaviour of magnetic and transport properties, connected with the granular structure of ceramic high temperature superconductorsAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio