Influence of Nano CeO₂ on the Microstructures and Current Density of Preform Optimized Infiltration Growth-Processed Bulk YBa₂Cu₃ O _7−δ Superconductors

Abstract

The effect of the addition of nanometric ceria (CeO₂) on the physical properties of YBa₂Cu₃ O _7−δ superconductors is investigated. Preform optimized infiltration growth (POIG) process emerged as one of the advanced processing techniques to obtain the uniform distribution of fine Y₂BaCuO₅ (Y-211) particles of the order of ∼1 μ m. Nanoparticles of CeO₂ were added to Y-211 in 0, 2, 5 and 10 wt% through a novel process called Nano Dispersive Sol Casting and subjected to POIG process. Nanometric CeO₂ particles were distributed homogeneously throughout the Y-211 preform without any agglomeration. The micrographs of the final composites indicate refinement in Y-211 particle size and presence of defects in various length scales, starting from few nanometers to few microns. As the CeO₂ content increased, the Y-211 particle size refined below 1 µm and, for 10 wt% of doping, even smaller than 0.5 µm. Elemental analysis confirmed the formation of different phases in the CeO₂-added composites, due to which the superconducting transition is shown broadening. The sample with 10 wt% doping exhibited a stable J _c curve to high applied magnetic fields due to the presence of multiple peak fields. The present work demonstrates the introduction of fine microstructural defects for pinning the flux lines at different applied magnetic fields in POIG-processed YBCO composites.