Microstructural properties of K0.8 Fe1.6 S2, K0.8 Fe1.75 Se2-y Sy(0 ≤ y ≤ 2) and K0.8 Fe1.5+x S2(0 < x ≤ 0.5) single crystals
1 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences Beijing 100190, PRC
2 School of Materials Science and Engineering, Hefei University of Technology - No. 193, Tunxi Road, Anhui Province, Hefei 230009, PRC
Received: 28 June 2013
Accepted: 5 August 2013
The structural features of the antiferromagnetic K0.8Fe1.6S2 have been studied in the temperature range from 300 K up to 700 K by means of in situ transmission electron microscopy (TEM). The superstructure with a wave vector originating from a Fe-vacancy order has been clearly observed; moreover, the structural analysis shows that K0.8Fe1.6S2 undergoes a transition from the Fe-vacancy order to disorder at about 585 K. The S substitution effect on the phase separation and superconductivity in the K0.8Fe1.75Se2−ySy materials has been systematically investigated by SEM and TEM structural analyses, as well as by electrical resistivity measurements. Our experimental results reveal that the S element adopts a homogeneous distribution in all investigated materials, and the essential phase-separation nature is very similar to what was observed in the K0.8Fe1.75Se2 superconductor. A phase-separated state formed by the coexistence of two Fe-vacancy orders with wave vectors and in K0.8Fe1.5+xS2 (0 < x < 0.1) has been briefly discussed.
PACS: 74.70.Xa – Pnictides and chalcogenides / 61.72.jd – Vacancies / 61.05.J- – Electron diffraction and scattering
© EPLA, 2013