Effects of carbon nanotubes addition on the superconducting properties and critical current density of NdBa2Cu3O7−δ

Polycrystalline NdBa2Cu3O7−δ samples with 0 to 1.5 wt% carbon nanotubes (CNTs) addition have been synthesized via the solid-state reaction method. The samples were examined by the four-point probe temperature-dependent electrical resistance, critical current density and AC susceptibility measurements. X-ray diffraction (XRD) patterns showed that the addition of CNTs did not change the orthorhombic structure of the samples and there was no systematic variation in the lattice parameters. CNTs addition increased the transition temperature with the highest onset transition temperature, Tc onset = 96 K for the 1 wt% added sample. The critical current density increased from 2600 mA/cm2 for the pure NdBa2Cu3O7−δ to 4960 mA/cm2 for the 1.0 wt% CNTs added sample. It is suggested that the grain boundaries improved with CNTs addition, and this plays an important role in the electrical transport properties. Addition of CNTs enhanced the flux pinning and improved the grain boundaries of high-temperature superconductors. The effect of CNTs on other cuprate high-temperature superconductors has also been compared with these NdBa2Cu3O7−δ samples.