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High‐Purity FeSe 1−x Superconductors Prepared by Solid‐State Synthesis and Liquid Phase Processing
Author(s) -
Qi Xiaoding,
Wang JiunYi,
Hung ChiJung,
Kuo JuiChao,
Yates Karen,
Cohen Lesley
Publication year - 2010
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.03912.x
Subject(s) - tetragonal crystal system , materials science , superconductivity , analytical chemistry (journal) , annealing (glass) , sintering , phase diagram , solid solution , phase (matter) , metallurgy , chemistry , condensed matter physics , chromatography , physics , organic chemistry
FeSe 1− x samples have been prepared by a solid‐state reaction in the Ar+3% H 2 gas flow. The samples sintered at 410°C were of the tetragonal PbO structure (β‐phase), showing little trace of δ‐phase (hexagonal). However, the samples sintered at higher temperatures contained a fair amount of δ‐phase, which was unable to be eliminated completely by subsequent annealing at ≤450°C for a prolonged period. Both M – T and R – T measurements showed that sintered samples of β‐phase were superconducting with an onset T c above 8.1 K. Thick films of FeSe 1− x were grown on LaAlO 3 substrates by liquid phase processing with SeSn as the flux. In contrast to the sintering, the films grown around 910°C from the Sn‐containing liquid had a pure β‐phase. Although the phase diagram showed some solid solubility of Sn in FeSe, energy‐dispersive X‐ray spectroscopy failed to find Sn trace in the crystallized films, which showed a steeper superconducting transition at lower T c of 6.0 K. To clarify whether the possible Sn contamination caused the drop of T c , FeSe 1− x :5% Sn samples were sintered, which showed little change of T c from the pure β‐FeSe 1− x . The cause for the T c reduction of thick films remains unclear.