Low-temperature synthesis of SmO0.8F0.2FeAs superconductor with Tc = 56.1K

TL;DR

This study systematically examines how sintering temperature affects the structure and superconducting properties of SmO0.8F0.2FeAs, revealing optimal conditions for achieving high Tc and critical current density in this superconductor.

Contribution

It provides new insights into the optimal sintering temperature (~1000°C) for maximizing Tc and Jc in SmO0.8F0.2FeAs superconductors, improving synthesis protocols.

Findings

Samples sintered at 1000°C achieved the highest Tc of 56.1 K.

Lower impurity scattering and higher carrier density at 1000°C.

Maximum Jc of 1.05×10^5 A/cm^2 at 5 K in samples sintered at 1100°C.

Abstract

We report a systematic study on the effect of sintering temperature on the structural and superconducting properties of nominal SmO0.8F0.2FeAs fabricated by simple one-step solid state reaction method. A detailed correlation between the sintering temperature, structure, onset transition temperature (Tc) and critical current density (Jc) has been found in all samples of each batch. Most importantly, samples sintered at a low temperature clearly shows high Tc, for example the Tc of the samples sintered at 850C is even above 53 K, and the samples prepared at 1000C display the highest Tc of 56.1 K reported so far. Furthermore, the samples sintered at 1000C also show the highest RRR and the lowest resistivity(57K), indicating the low impurity scattering and enhanced carrier density. However, the maximum Jc of 10510 A/cm^2 at 5 K in self field was achieved in the samples sintered at 1100oC. The dependence of Tc on a-axis lattice constant indicates that the sintering temperature has strong influence on the effective substitution level of F for O. This result suggests that annealing at a temperature of ~1000C seems much better for obtaining high quality 1111 phase oxypnictides, compared to commonly used temperatures of around 1200C.