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The iron-pnictide Sm1−xCaxFeAsO1−2xF2x superconductor was prepared and the combined effect of electron and hole doping was studied in detail. It is observed that the binary doping using CaF2 improves the microstructure tremendously with a preferred orientation of the (00l) planes. Moreover, a maximum TC of 53.8 K and a transport JC of 880 A/cm2 (12 K), which is double to that of the F-doped sample, are achieved. The dopant CaF2 seems to be a potential candidate for solving the grain-connectivity concerns in iron-pnictides paving the way towards conductor development.

A comparative study on the effect of doping of nano carbon, nano diamond and nano SiC in MgB2 is carried out.The JC(H) is significantly enhanced for all doped samples compared to the pure sample among which MgB1.9C0.1 (nano C) exhibits the best JC(H) performance. The enhanced performance is due to the effective substitution of C at B site which is confirmed by the systematic decrease in both a axis and TC.

The effects of addition of nano SiO2 and/or nano diamond on structural and superconducting properties of MgB2 bulk samples were studied. The addition caused systematic reduction in ‘a’ lattice parameter. The in‐field critical current density [JC(H)] of doped samples showed a significant enhancement compared to the undoped sample. The codoped samples exhibited the best results.

A small amount of nano Cu addition (2.5 wt %) was found to dramatically decrease the reaction temperature of magnesium and boron, forming MgB2 without any degradation in the transport critical current. The presence of reacted Mg2Cu liquid phase could accelerate the reaction between Mg and B and finally results in the formation of MgB2 phase even at low temperatures. All Cu doped samples heat treated below 650 °C exhibited highly enhanced transport JC at 30 K and the sample heat treated at 550 °C recorded 30‐fold increase in transport JC compared to the pure sample.