TY - JOUR
T1 - The Synthesis, Structural Characterization and Superconductivity of $FeSe_x$ with $0.80 \leq x \leq 1.20$
AU - Shen , Xiao-Li
JO - Journal of Atomic and Molecular Sciences
VL - 1
SP - 89
EP - 94
PY - 2012
DA - 2012/03
SN - 3
DO - http://doi.org/10.4208/jams.040311.051411a
UR - https://global-sci.org/intro/article_detail/jams/8275.html
KW - iron-based superconductors, $FeSe$, synthesis.
AB - <p style="text-align: justify;">We have performed a detailed study on the synthesis, the characterization of structural phases and superconductivity of the binary $FeSe_x$ system from the $Fe$-rich phase into 
the $Se$-rich phase with $0.80 ≤ x&nbsp;≤1.20.$ The results indicate that by long-time low-temperature annealing, single phase sample could be obtained near the composition of $FeSe_{0.95}$&nbsp;with the tetragonal PbO-type structure, while impurities of $Fe$ or $Fe_7Se_8$ would appear if Fe enriched or $Se$ enriched in the starting composition respectively. 
Bulk superconductivity was found to exist in highly $Se$ deficient phase, but not the single phase, and superconductivity is very sensitive to the $Se$ vacancy content. The anomalous 
downturn of resistivity around 100 K was eliminated in Se-rich phase, along with the suppression of the main superconducting phase.</p>