Improvement in granularity of NdFeAsO0.8F0.2 superconductor through Agx doping (x = 0.0–0.3)

TLDR: In this paper, the impact of silver addition on granularity of NdFeAsO 0.8 F 0.2 superconductor was investigated and the results showed that limited addition of Ag improves the granular coupling of superconducting grains of NdyFeAs o 0.

Abstract: We report the impact of silver addition on granularity of NdFeAsO 0.8 F 0.2 superconductor. The ac susceptibility and electrical resistivity under magnetic field are measured to study the improvement in weak links of NdFeAsO 0.8 F 0.2 with addition of Ag x ( x  = 0.0–0.3). The Ag free NdFeAsO 0.8 F 0.2 compound shows superconductivity at around 51.8 K. Typical two step superconducting transitions due to the inter- and intra-grain contributions, induced from the combined effect of superconducting grains and the inter-granular weak-coupled medium respectively are clearly seen in susceptibility [ χ ( T )] plots. In comparison to the pure NdFeAsO 0.8 F 0.2 compound, the coupling between the superconducting grains is significantly improved for 20 at% silver doped sample, and the same is deteriorated for higher Ag content i.e., for 30 at%Ag sample. The magneto transport measurements ρ ( T ) H of polycrystalline 20 at% Ag doped NdFeAsO 0.8 F 0.2 exhibited the upper critical filed [ H c2 (0)] of up to 334 T, which is slightly higher than the one observed for pure NdFeAsO 0.8 F 0.2 . The flux flow activation energy ( U 0 / k B ) varies from 7143.38 K to 454.77 K with magnetic field ranging from 0 T to 14 T for 20 at% Ag doped NdFeAsO 0.8 F 0.2 . In this investigation, our results show that limited addition of Ag improves the granular coupling of superconducting grains of NdFeAsO 0.8 F 0.2 compound.