Improvement of Jc of Ag-Sheathed Bi-2212 Tapes Using Melt-Growth Technique under Reduced Oxygen Partial Pressure

Abstract

The growth behavior of Bi-2212 under the oxygen partial pressure of 0.01 atm has been investigated using Ag-sheathed tapes. In the partial melt state, a Cu-free phase and (Sr, Ca)CuO₂ have been observed as solid phases. The Cu-free phase has been assigned, tentatively, as Bi₂Sr₂CaO₆. The grain size of the Cu-free phase has been found to depend critically on the starting composition. It decreases as the Sr content increases and the Ca content decreases, and accordingly, J _c of the melt-processed tapes increases. The optimum composition is Bi₂Sr_2.3Ca_0.85Cu₂O _z and the maximum J _c is 1.5×10⁵ A/cm² at 4 K.