Phase separation and stripe patterns in K0.8Fe1.6+xSe2 superconductors
  Structural investigations on the K0.8Fe1.6+xSe2 superconducting materials have revealed remarkable micro-stripes arising evidently from the phase separation. Two coexisted structural phases can be characterized by modulations of q1 = 1/5[a*+3b*], the antiferromagnetic phase K0.8Fe1.6Se2, and q2 = 1/2[a*+b*], the superconducting phase K0.75Fe2Se2, respectively. These stripe patterns likely result from the anisotropic assembly of superconducting particles along the [110] and [1-10] direction. In addition to the notable stripe structures, a nano-scale phase separation also appears in present superconducting system as clearly observed by high-resolution transmission electron microscopy. Certain notable experimental data obtained in this heterogenous system can be quantitatively explained by the percolation scenario. 
Z. W. Wang, Z. Wang, Y. J. Song, C. Ma, H. L. Shi, Z. Chen, H. F.   Tian, H. X. Yang, G. F. Chen and J. Q. Li
cond-mat.supr-con