The discovery of superconductivity at relatively higher temperatures in a non-cuprate system, LnFeAsO 1−x F x (Ln = lanthanides) has created tremendous activity among the reseachers in this field. This review is an overview on the present status and the future scope for iron pnictides. The various structural categories of iron based superconductors, the structural aspects, different preparation techniques of the material and the necessity for its optimization are discussed. The highlighting features of iron pnictide, i.e. the very high upper critical field, moderate magneto-transport and thermal properties, are also included. The article gives a summary of the prevailing arguments of researchers to relate the material to cuprates and also the comparative features of classical and MgB 2 superconductors. The existing challenges, such as optimizing synthesis methods for technological applications and clarifying the ambiguity in the superconducting mechanism and the flexibility of the material for any site substitution, will keep iron based superconductors on the frontiers of research for a long time, in parallel to HTS.

The critical current density and flux pinning properties of Bi1.6Pb0.5Sr2−xEuxCa1.1Cu2.1Oy (where x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) prepared by solid state synthesis in bulk polycrystalline form were studied. The samples were characterized by powder x-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy-dispersive x-ray analysis (EDS) and superconductivity measurements. The critical temperature (TC), critical current density (JC) and field dependence of JC of the Eu-substituted samples were found to be highly enhanced for optimum doping levels. The peak position of the normalized pinning force density (Fp/Fpmax) is found to shift to higher fields (0.88 T) for optimally doped samples in contrast to 0.2 T for the undoped sample. The enhancement of the JC–B characteristic and pinning force density FP (FP = JC × B) due to Eu substitution is of great technological significance.

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