Effect of Various Pinning Centers on Electric and Magnetic Transport Properties in YBa2Cu3O7-δ

Abstract

Among all High Tc superconductors, YBa2Cu3O7-δ is widely studied material because of its superior property of low anisotropy and high current carrying capacity. The existence of Abrikosov vortices in the mixed state in Type-II superconductors form triangular flux-line lattice that remain unpinned in an ideal defect free superconductor. In order to achieve high critical current density at high magnetic field vortex must be pinned. So the concept of artificial pinning centers was introduced to facilitate efficient pinning in type-II superconductors. The artificial pinning centers are inhomogeneities of nano-metric or micronized particles that act as potential barrier to pin vortex core by enhancing critical current density. The present work aims at studying the various aspects i.e. structural modification, microstructural
changes, electrical and magnetic transport property in a YBCO composite system. In this thesis superconducting samples have been prepared by different routes such as bulk sintered through solid state reaction, thick film by diffusion reaction and thin film by pulsed laser deposition. The composite material chosen are well known reported pinning centre i.e. ferroelectric BaTiO3 (BTO), Carbon Nano Tube (CNT), Y2O3 insulator, Ag metal conductor and amorphous ion track (columnar defect). Further, the work focuses on dual defects i.e. combining of Y2O3 and columnar defect in YBCO thick fil prepared by diffusion reaction as well as combining Ag and columnar defect in pulsed laser deposited (PLD) film. The columnar defect has been induced by 200 MeV Ag ions.