New superconducting phase of Sr2CuO2+δCl2−ywith 0201-type structure synthesized under high pressure

K2NiF4-type Sr2CuO2+δCl2–y superconductor was synthesized with partial substitution of oxygen for apical chlorine using a high-pressure technique. This phase has been studied by transmission electron diffraction, convergent beam electron diffraction, x-ray powder diffraction, energy dispersive analysis of x-ray, electron energy loss spectroscopy and high-resolution electron microscopy. The crystal structure with a space group of I4/mmm has been determined, and the lattice parameters are obtained as a = b = 0.394 nm and c = 1.564 nm. Edge dislocations with Burgers vector are observed in the phase.