On the Effect of Carbon Nano-Tubes Addition on Structure and Superconducting Properties of Bi(Pb)-2223 Phase

In this work, a series of ceramic samples of Bi1.6Pb0.4Sr2Ca2Cu3O y (Bi(Pb)-2223) added with different amounts (0, 0.2 and 0.4 wt%) of carbon nano-tubes (CNT) are prepared from commercial powders and characterized. The study shows that the volume fraction of the Bi(Pb)-2223 phase decreases with CNT content while the grain size of the samples increases. The obtained cell parameters as well as the onset critical transition temperature are independent of this kind of addition. Also, it has been concluded that CNT addition makes the grains of the samples more connected. The measured magnetization in FC and ZFC modes indicates that CNT addition makes the grains of the samples more connected even if the irreversibility line is decreased. The variation of the residual resistivity and metalicity with CNT content suggests that the addition introduces disorder and defects into the samples. Also, the added samples present broad transitions to the superconducting state when compared to the pure one; this result may be associated to the increase of the volume fraction of the secondary phases. The activation energies, upper critical fields H c2(0) and coherence lengths ξ(0) are extracted from the magneto-resistivity curves and their evolutions with CNT content are discussed.