The Comparisons Between Y-123 and Y-124 Superconductor Substituted with Ca at the Cu-Site

Abstract

The comparison between YBa2Cu3−x Ca x O δ and YBa2Cu4−x Ca x O8 superconductors substituted with Ca at the Cu-site was investigated. The concentration of Ca varied from x=0.00 to x=0.15. Resistivity and current density measurement (without magnetic field) were measured using four-probe method. The samples were characterized using X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). From the resistivity measurement, the critical temperature (T c zero) in x=0.00 was 84 K for Y-123 and 83 K for Y-124 superconductor system. As the Ca concentration increased to x=0.15, both superconductor systems showed a decrease in value whereby 71 K for Y-123 and 74 K for Y-124. This was a result of the decrease in the hole concentration. Critical current density (J c ) decreased with the further increment of Ca concentration owing to grain connectivity and an increase of porosity. At 50 K, J c decreased from 3.9790 A/cm2 at x=0.00 to 3.5184 A/cm2 at x=0.15 for Y-123, and from 3.6209 A/cm2 at x=0.00 to 0.5243 A/cm2 at x=0.15 for Y-124. The crystallographic crystal structure showed that both Y-123 and Y-124 superconductor systems exhibited an orthorhombic form. FESEM microscopy showed that the Y-123 sample had less porosity compared to Y-124 samples and the resulting Y-123 sample had a higher J c compared to the Y-124 sample.