NdFeAsO_1−xF_x Superconductor – Impact of Fluorine Variation on Microstructure and Transport Properties

Abstract

Polycrystalline samples of NdFeAsO1−xFx (Nd1111) with x = 0, 0.1, 0.2, 0.3, and 0.4 were synthesized using a solid‐state method at ambient pressures. A maximum transition temperature (TC) of 52.0 K and a JC of 1050 A/cm2 at 12 K were observed for x = 0.3 and 0.4, respectively. The transport and magnetic properties observed for each stoichiometry have remarkable correlation with their corresponding structural and microstructural aspects. Moreover, the superconducting properties exhibited in this material, processed at a relatively low temperature of 1000°C, are competitive as compared to the existing reports wherein high pressures/temperatures are inevitable.

Influence of Reactivity of Sheath Metals on the Superconducting Properties of NdFeAsO_0.₆F_0.₄ Wires

“…This corresponds to a critical current density J C (J C = I C /A where A is the cross sectional area of the superconducting core) of 3250 A/cm 2 . The T C and J C values obtained for the wire samples are higher than the bulk samples of similar stoichiometry [4]. Thus, it is clear that in situ powder-in-tube technique using pre-processed sample has been effective in controlling the volatile loss of fluorine thereby enhancing the superconducting properties.…”

“…zero voltage, instead it shows a tendency of superconducting transition. The Ag sheathed wire sample shows an onset T C of 57 K, higher than the T C obtained for the corresponding bulk sample [4]. The superconducting sample was then subjected to I-V measurements at 12 K, shown in inset of Fig.…”

Microstructural refinement and enhanced transport properties in binary doped NdFeAsO superconductor

“…The observation is in agreement with the reported result that microstructure improves with the increase in fluorine doping level. 20 In binary doped samples, a remarkable change is observed both in grain connectivity and grain size. The preferred orientation of crystallites along c-axis as found from the XRD analysis and the observed decrease in FWHM of the binary doped samples, especially in NdCa2, are clearly reflected in the corresponding SEM images.…”

SmFeAsO Superconductor with Preferred Crystallographic Orientation and Enhanced Critical Current Density

“…Polycrystalline bulk samples were prepared by a three‐stage heat‐treatment process . Samples with nominal compositions of Sm 1− x Ca x FeAsO 1−2 x F 2 x with x = 0.15, 0.2 were synthesized by stoichiometric mixing of Sm, Fe, As, Fe 2 O 3 , and CaF 2 powders.…”