Study of the thermo-magnetic fluctuations in carbon nano-tubes added Bi-2223 superconductors

Abstract We have investigated the effect of addition of carbon nano-tubes (CNT) on the properties of Bi 1.6 Pb 0.4 Sr 2 Ca 2 Cu 3 O y superconductors. The samples are prepared from commercial powders with addition of 0.1 wt% of CNT. They are characterized by XRD, SEM and magneto-resistivity in the transition region. As it was reported for CNT added Y-123 compounds, the refined cell parameters are practically independent of this kind of addition. Under applied magnetic field, a large broadening of resistive transition is observed. The dissipative behavior of resistivity can be explained using the well known expression, ρ=ρ 0 ( T / T g −1) S . The modified vortex-glass to liquid transition theory is used to calculate the values of the glass-transition temperature T g and the temperature and magnetic field dependent activation energy U 0 ( B , T ). These parameters are seen to decrease with CNT addition and applied magnetic field. Also, we have found that the undoped sample proves a better transition width, residual resistivity ( ρ 0 ) and a higher onset critical transition temperature of about 117.75 K. Also, the appearance of a double resistive transition for both samples is a confirmation of the existence of a secondary phase which plays the role of the weak links at the grain boundaries.