Ni Nanoparticle-Added Ni x /(Cu 0 . 5 Tl 0 . 5 )Ba2Ca2Cu3 O 10-δ Superconductor Composites and Their Enhanced Flux Pinning Characteristics

Abstract

Ni nanoparticle-added Ni x /(Cu0.5Tl0.5)Ba2Ca2 Cu3 O 10-δ superconductor composites are synthesized at normal pressure by two-step solid-state reaction method. The idea for adding ferromagnetic nanoparticles was to create artificial pinning centers at grain boundaries. The samples have shown orthorhombic crystal structure in which the cell parameters increase with an increase in the added concentration of Ni nanoparticles. This shows that due to the higher reactivity, Ni nanoparticles partially diffuse into the unit cell of (Cu0.5Tl0.5)Ba2Ca2Cu3 O 10-δ superconductors. This also indicates as an evidence of the occupancy of these nanoparticles at grain boundaries. A metallic variation of resistivity from room temperature down to the onset of superconductivity is a typical feature of these samples with T c (R = 0) varying between 92 and 94 K. The magnitude of diamagnetism is significantly enhanced in 7 and 10% nanoparticle-added samples. The enhanced magnetization of ferromagnetic nanoparticles at reduced temperature plays a vital role in reducing the diamagnetism of nanosuperconductor composites. The softening of apical oxygen modes of type Cu(1)–OA–Cu(2) has confirmed the diffusion of Ni nanoparticles into the unit cell of the final compound. The excess conductivity analyses of conductivity data have shown that the values of B c (0), B c1, and J c are enhanced with the addition of Ni nanoparticles in the final compound. Variation of superconducting properties was attributed to pair breaking due to spin scattering across these ferromagnetic Ni nanoparticles. This shows that added Ni nanoparticles act as efficient pinning centers, which is also confirmed by the suppression of the London penetration depth.