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

The effects of neodymium (Nd) addition on the phase evolution, structural and superconducting properties of (Bi,Pb)2Sr2CaCu2Oy [(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 (TC) and the critical current density (JC) 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/cm2 at 64 K (x = 0.2) against 76.7 K and 100 A/cm2, 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’.