Superconductivity of Y2O3 and BaZrO3 nanoparticles co-added YBa2Cu3O7−δ bulks prepared using co-precipitation method

In this work, polycrystalline samples of nominal composition YBa 2 Cu 3 O 7−δ with co-addition of 5.0 mol% of Y 2 O 3 and x mol% of BaZrO 3 (BZO) nanoparticles ( x = 0.0, 1.0, 2.0, 3.0, 5.0 and 7.0) were prepared using co-precipitation (COP) method. Data of X-ray diffraction (XRD) showed that all the samples were composed of Y-123 as the major phase and Y-211 as the minor phase. XRD peak of BZO was also observed in the samples co-added with BZO nanoparticles. Refinement of lattice parameters of a, b , and c -axis showed that the orthorhombic structure of the samples was retained without occurance of orthorhombic-tetragonal phase transition. The average grain size was increased from 0.30 ± 0.02 µm for the pure sample to 0.47 ± 0.03 µm for the sample with 7.0 mol% BZO as revealed by the scanning electron microscope images. Plots of normalized resistance versus temperature showed metallic behavior in the normal state and a single step transition in the samples. T c-onset was decreased with co-addition of Y 2 O 3 and BZO probably because of reduced hole concentration. The higher Josephson’s current, I o of the samples with co-addition of 0.0–2.0 mol% BZO compared with that of the pure one is likely to be due to improved grain coupling as shown by the AC susceptibility measurement. The calculated intergranular critical current density, J cm based on the Bean critical state model is 1.88 A/cm 2 at T p = 84.8 K for the pure sample. The highest J cm obtained is 2.10 A/cm 2 at T p = 85.4 K for 2.0 mol% BZO co-added sample.