Superconducting phase with Tc of 17 K in La2CuO4+δ

A single-phased La2CuO4+δ sample with Tc of 17 K prepared by electrochemical oxidation is reported in this paper. Its structural and physical properties are studied by X-ray diffraction, resistance, magnetic susceptibility and thermopower measurements for the first time. It is found that the hole concentration is around 0.12, and the structure is pseudo-tetragonal. The Tc suppression, compared with other Tc’s in La2CuO4+δ system, is considered to be an indication of the “stripe pinning” in the La2CuO4+δ related to the famous “1/8 problem”.