Özet:
Bulk superconductor samples of YBa2Cu3O7-δ (YBCO or Y-123), with additions of 0.15 wt% MoO3, TiO2, RuO2 and two different types of Al2O3 compounds, are synthesized by a solid state reaction route. Structural, magnetic and transport properties of the samples are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), magnetic (M-H, M-T) and magneto-resistivity (MR-T) measurements. SEM investigations show that the addition of the Al2O3 obtained from the alumina crucible (Al2O3-cru) decreases the grain size of the sample which, in turn, degrades the transition temperatures (Tc) and magnetic critical current densities (Jcmag). On the contrary, the addition of the other metal oxides enhances Jcmag of the samples by a few times and also increases Tc by up to 3 K. EDX analyses of the samples exhibit homogeneous distribution of additions, except for Ru-heterogeneities located around superconducting Y-123 grains. The highest Jc and Tc values obtained on the RuO2 added sample were attributed to the agglomeration of the Ru-particles, which led to the optimal porosity that supports oxygenation process and intergrain coupling of the structure. From the DC magnetization data, we estimated Jcmag of 3.1 × 105 A/cm2, 2.3 × 105 A/cm2, 2 × 105 A/cm2, 1.5 × 105 A/cm2, 105 A/cm2 and 5.1 × 104 A/cm2 for the RuO2, TiO2, MoO3, Al2O3, undoped and Al2O3-cru added samples at 5 K under 0.25 T, respectively. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.