The Comparisons Between Y-123 and Y-124 Superconductor Substituted with Ca at the Cu-Site
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O R I G I N A L PA P E R
The Comparisons Between Y-123 and Y-124 Superconductor Substituted with Ca at the Cu-Site H.N. Hidayah · S.Y. Yahya · H. Azhan · K. Azman · J.S. Hawa · A.W. Norazidah
Received: 5 November 2012 / Accepted: 1 December 2012 / Published online: 20 December 2012 © Springer Science+Business Media New York 2012
Abstract The comparison between YBa2 Cu3−x Cax Oδ and YBa2 Cu4−x Cax 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 (Tc 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 (Jc ) decreased with the further increment of Ca concentration owing to grain connectivity and an increase of porosity. At 50 K, Jc 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 Y123 sample had less porosity compared to Y-124 samples and the resulting Y-123 sample had a higher Jc compared to the Y-124 sample.
H.N. Hidayah () · S.Y. Yahya · J.S. Hawa · A.W. Norazidah Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia e-mail: [email protected] H. Azhan · K. Azman Faculty of Applied Sciences, Universiti Teknologi MARA Pahang, 26400 Jengka, Pahang, Malaysia
Keywords Ca substitution · Critical temperature · Cu-site · Y-123 · Y-124
1 Introduction The YBa2 Cu4 O8 superconductor system was discovered [1] a year later after the discovery of the YBa2 Cu3 Oδ superconductor [2]. The difference between these two phase superconductors is the Cu–O chain, whereby the Y-123 superconductor contains a single layer of Cu–O chain compared to the Y-124 superconductor, which contains a double layer of Cu–O chain. An additional Cu–O chain in Y-124 superconductor results in no phase transformation from orthorhombic to tetragonal, which contrasts with the Y-123 superconductor [3]. Like other types of high Tc superconductor, these two phases of the YBCO superconductor system also have their limitation owing to a poor mechanical and brittle nature [4]. Various elemental substitution, addition and doping were used to improve the performance of the YBCO system. The substitution of alkaline-earth metal has been reported to increase the Jc [5, 6]. The substitution of Ca onto the Y-site of Y-123 and Y124 phase systems has been re
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