Synthesis of superconductor Bi-2223 and its properties after partial oxygen substitution

摘要

In the first part of the work two routes of preparation of undoped superconductor Bi-2223 are compared. The influence of addition of extra PbO is studied as well. The route that leads to higher content of the phase 2223 is then chosen as the appropriate way for preparation of fluorine doped samples of general stoichiometry Bi_(1.6)Pb_(0.4)Sr_2Ca_(2.5)Cu_(3.5)O_(x-z),F_z (z = 0, 0.3, 0.6 and 0.9). These samples are characterized by measuring of their temperature dependence of electrical resistance and critical current density. Their phase composition is determined by XRD. While greater amount of fluorine widenes the superconducting transition and worsenes transport properties, the less doped sample shows increasement of critical current density.