Structural and superconducting properties of neodymium added (Bi,Pb)(2)Sr2CaCu2Oy

Abstract

The effects of neodymium (Nd) addition on the phase evolution, structural and superconducting properties of (Bi,Pb)(2)Sr2CaCu2Oy [(Bi,Pb)-2212] prepared by solid state synthesis in bulk polycrystalline form were studied. The Nd content was varied from x = 0 to 0.5 on a general stoichiometry of Bi1.7Pb0.4Sr2.0Ca1.1Cu2.1NdxOy. The samples were characterized by differential thermal analysis (DTA), powder X-ray diffraction, scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX), resistance-temperature (R-T) measurements and superconductivity measurements at 64 K. It was found that the melting temperature of (Bi,Pb)-2212 slightly increases and the endotherm broadens due to the Nd-addition. The c-lattice parameter initially decreases and then increases with Nd addition. The critical temperature (T-C) and the critical current density (J(C)) of the added samples are highly enhanced. The added sample shows a maximum onset critical temperature (TC-onset) of 95.56 K (x = 0.3) and a maximum critical current density of 719 A/cm(2) at 64 K (x = 0.2) against 76.7 K and 100 A/cm(2), respectively, for the pure sample. The results show that the enhancement in superconducting properties are not due to any improvement in microstructure or grain growth, but due to a decrease in hole concentration as a result of Nd doping, which changes the system from 'over-doped condition' to 'optimally doped condition'