Annealing effect on high-pressure oxygen for (As0.33Cu0.67)Sr2YCu2Oy

We investigated the new layered copper oxide, (As0.33Cu0.67)Sr2YCu2O7.17. I t had an anomalous change in resistivity below 60 K. However, resistivity a nd magnetic susceptibility measurements showed that (As0.33Cu0.67)Sr2YCu2O7 .17 was not superconducting but semiconducting. From the X-ray diffraction data, it was found that nonsuperconductivity of (As0.33Cu0.67)Sr2YCu2O7.17 comes from the existence of two oxygen sites in the (As, Cu)O-7.17 layer. I n order to increase the oxygen content, annealing under high oxygen pressur e (450 atm) at 400 degreesC for 19 h was carried out. The specimen did not show superconductivity yet but showed a metallic property together with a d rastic decrease in resistivity. (C) 2001 Elsevier Science B.V. All rights r eserved.