Impurity effects on activation energy, structure and physical properties of Ybco superconductor

Abstract

The influence of separately added 0.3 wt%, CdO, Bi2O3, BeO and SiO2 on the phase formation, microstructure, magnetic and transport properties of Y1Ba2Cu3O(7-$\delta$)  (Y-123 or YBCO) fabricated by conventional solid state reaction method has been analyzed. The results reveal a very low solubility limit for bismuth and silicon in the Y-123 phase, leading to precipitation phases located within intergranular regions. BeO addition suppresses the granular nature of the structure by probably incorporating into the host matrix. CdO does not have a remarkable effect both on structural and superconducting properties of the Y-123 at this doping ratio. Attractive infield transition behavior was obtained in the Bi2O3 added sample with a narrower transition width and an increase of transition temperatures approximately 1 K. The activation energy (U0), a potential energy barrier to prevent flux flow, of the samples was estimated by taking into account Arrhenius law. The best U0 value was computed to be 1.11 eV belonging to the Bi2O3 added sample which implies the contribution of 3-5 µm sized Bi containing precipitation regions on the flux pinning capability of the Y-123.