Synthesis and Microstructural Studies of Iron Oxypnictide LaO1-xFxFeAs Superconductors

TL;DR

This study reports the synthesis of fluorine-doped LaOFeAs superconductors at lower temperatures, revealing microstructural features and a superconducting transition temperature of 27.5 K, with implications for understanding high-Tc oxypnictides.

Contribution

It introduces a new synthesis method at lower temperature and longer duration, and identifies a secondary structural phase in LaOFeAs superconductors.

Findings

Superconducting transition temperature of 27.5 K at x=0.2 doping.

Existence of a secondary structural phase with c ~12.67A.

Microstructural analysis suggests a modulated structure similar to cuprates.

Abstract

We report on the synthesis and structural/ microstructural studies of iron based fluorine doped LaOFeAs superconductors. We have successfully synthesized fluorine doped superconducting LaO1-xFxFeAs materials by choosing lower temperature (1150^0C) and longer synthesis duration (60 hours) as compared to the standard values of these employed in the pioneering first contribution [Kamihara et al 2008 J Am Chem Soc 130 3296]. Decrease of lattice parameters as determined by x-ray diffraction confirm the substitution of fluorine. The superconducting transition temperature is 27.5 K which is observed at doping level of x=0.2. This superconducting material LaO1-xFxFeAs exhibits interesting microstructural characteristic. This relates to the existence of another structural phase, besides the standard phase, having c parameters of ~12.67A. This suggests existence of modulated structure, similar to the cuprates, in these new oxypnictides. This phase may have new impacts on this new high-Tc family.