Effect of composition on critical current density of Bi2212/Ag round wires

We have fabricated Bi2212/Ag round wires using three kinds of precursor to study the effect of a narrow variation of composition. Slightly different compositions - Bi_2.17Sr_1.94Ca_0.89Cu_2.0O_x(N13), Bi_2.15Sr_1.94Ca_0.89Cu_2.0O_x(N14), and Bi_2.17Sr_1.98Ca_0.89Cu_2.0O_x(N15) - were used and Sr/Ca ratio of them were 2.18, 2.18, and 2.22, respectively. The Ag ratios of the wires were 2.7-2.8 and average filament diameter was 19-21 μm. DTA analysis of the wire showed the peritectic temperature of three wires was very similar value of the range of 880-881 °C. The best engineering critical current density (J_e) of three wires at 4.2 K and 0 T was 414-448 A/mm² at the maximum process temperature range of 884-892 °C. The n-value of N14 showed 13.6, whereas other two wires showed lower n-value, estimating the existence of micro-cracks. Although Bi2212/Ag round wires fabricated by three kinds of composition showed similar J_e value, n-value was quite different. It is likely that the fabrication process such as the drawing as well as the composition of precursor will affect on J_e of Bi2212/Ag round wire.