High pressure synthesis of a new superconductor Sr2CuO2+xCl2-y induced   by apical oxygen doping
  Using the apical oxygen doping mechanism, i.e. a partial substitution of divalence O for the monovalence Cl, a p-type oxychloride cuprate superconductor, Sr2CuO2+xCl2-y, was synthesized at high pressure high temperature. The x-ray diffraction refinement suggests the superconductor crystallizes into a 0201 structure with space group I4/mmm and lattice parameters being a=3.92A, c=15.6 A. The magnetic susceptibility as well as resistance measurements indicated that the bulk superconductivity with transition temperature 30K was achieved in the sample. 
Q.Q. Liu, X. M. Qin, Y. Yu, F. Y. Li, C. Dong, C. Q. Jin