本文报道了采用自助溶剂法对不同组分K0.8Fe2-ySe2单晶生长和结构研究的实验结果.X-射线衍射XRD（Cu靶和同步辐射）结构分析表明样品中存在两套衍射峰（分别对应相1和相2）,相1能够用ThCr2Si2结构,空间群I4/mmm（No.139）指标化,对应超导相.而相2能够用单一米勒指数（0 0l）标定,可能对应一个新的物相.相2的存在能够在不同组分的KxFe2-ySe2单晶样品中很好的重复.利用高分辨透射电子显微镜（TEM）研究了K0.8Fe2Se2样品的＂结构相分离＂特征,结果表明样品中存在明显的位错缺陷,可能与两相结构的竞争有关.对K0.8Fe2Se2单晶样品直流磁化测量表明相2可能为弱铁磁性,从而引起高温Tp～125K的ZFC与FC磁性反常.
In this paper, we reported the results of single crystal growth and structure study of various stoichiometric K0.8Fex-ySe2 iron-selenides, which were grown by self-flux method. Two phases corresponding to phase 1 and phase 2 were detected by perfomaing both Cu target and synchrotron x-ray diffractions, in which phase I could be indexed to tetragonal ThCr2Si2-like structure with space group I4/mmm （No. 139） and be related to superconductivity. However, the series reflections of phase 2 could also belong to a single Miller index （0 0 1）,indicating a new structural phase. The phase 2 could be reproduced in various stoichiometric K0. 8 Fe2-y Se2 samples. The dislocation defects were observed in K0. 8 Fe2 Se2 crystal in TEM measurement, as may be connected with the competition between two phases. The measurement of temperature dependent magnetization On K0. 8 Fe2 Se2 crystal showed that phase 2 might be weak ferromagnetism and be responsible for the high temperature magnetic abnormality at Tp-125K.
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