Distinctive Effects between Hydrothermal and Ultrasound Synthesized SnO2 Nanoparticles on Ceramic Bi1.6Pb0.4Sr2Ca2Cu3O10+δ Superconductor

The effect of additions of two series of SnO2 nanoparticles synthesized using two different methods on crystal structure and superconductivity of Bi1.6Pb0.4Sr2Ca2Cu3O10+δ (BPSCCO) superconductors was investigated. Two series of spherical SnO2 nanoparticles were synthesized independently by using ultra-sonication (US-SnO2) and hydrothermal (HT-SnO2) methods. Polycrystalline samples of (Bi1.6Pb0.4Sr2Ca2Cu3O10+δ)1−x(SnO2)x, where x ranged between 0, 0.002 and 0.004, were fabricated by the solid-state reaction method. X-ray diffraction patterns showed a decrease in the volume fraction of the Bi-2223 and an increase in that of the Bi-2212 phases. Scanning electron microscopy images presented the “needle-like blossom” on the surface of the US-SnO2 doped samples, while the phenomenon was not found on the HT-SnO2 doped samples. The Tc was decreased extremely with US-SnO2 doping while slightly HT-SnO2 nanoparticle-doped samples. The field dependence of Jc, Jc(B), showed the opposite tendencies on two series of samples: Jc(B) was enhanced on the HT-SnO2 nanoparticle-doped samples, and that was decreased on UT-SnO2 nanoparticle-doped samples. The application of the Dew-Hughes model to explore the flux pinning mechanism exhibited that the point-like pinning centers were dominant on the HT-SnO2 doped samples. On US-SnO2 doped samples, however, the additional pinning center type was not found and could be explained by the observed over-sized SnO2 nano-needle.