ELECTRICAL AND MAGNETIC-PROPERTIES OF HONEYCOMB-TYPE BI(PB)-SR-CA-CU-O SUPERCONDUCTORS

Bi2O3, PbO, SrCO3, CaO and CuO compounds have been dissolved in liquid ammonium nitrate in order to produce Bi1.8Pb0.2Sr2Ca2Cu3O10 (2223) su perconductors of honeycomb-type structure. The resulting metal nitrate and nitrate complexes have been decomposed in an environment activate d by the exothermic reaction. Powders, homogeneous on the molecular sc ale, containing the binary and ternary oxides as the necessary constit uents have been produced. Samples in the form of pellets have been ann ealed at 845 degrees C for 25-125 h. This honeycomb-type BSCCO superco nductor with a critical temperature T-c=110 K and a density of 3 g cm( -3) has been produced. The volume of the sample has increased by about 25%-40% after annealing. Electrical and magnetic properties of the sa mples have been investigated in three regions: the superconducting reg ion T<T-c, the region T-c<T<T-c+Delta T-F where the Flicker effect has been observed (Delta T-F=20 K), and the normal region T>T-c+Delta T-F . It has been found that it is possible to have a controllable variati on in critical current density and that the optimum annealing time was about 100 h in order to obtain its maximum value.