A NEW HIGH-T-C SUPERCONDUCTING INTERCALATION COMPOUND

A new high-T-c superconducting intercalation compound, AgIBi2Sr2CaCu2Oy, has been prepared either by reacting the silver metal directly with Bi2Sr2CaCu2Oy powders under P(I-2) similar to 1atm. at 190 degrees C or by the intercalation reaction between the iodine-intercalated Bi2Sr2CaCu2Oy and AgI. According to the X-ray diffraction analysis, the observed basal increase of 7.35 Angstrom upon silver iodide intercalation indicates that the lattice expansion for AgIBi2Sr2CaCu2Oy is twice as large as that for the first-staged iodine-intercalated Bi2Sr2CaCu2Oy(Delta d approximate to 3.6 Angstrom). Such a result suggests the gallery contains a double layer of iodine. A slight decrease in T-c for the AgIBi2Sr2CaCu2Oy (T-c approximate to 63K) compared to the pristine (T-c approximate to 76K) has been observed by the d.c magnetic susceptibility measurements. The X-ray absorption spectroscopic results show that there is no charge-transfer between guest species (AgI) and host lattice. It confirms again that interblock-coupling has little effect on the superconductivity, since the T-c is not significantly evolved upon AgI intercalation with a large lattice expansion along the c-axis which is perpendicular to the (Cu-O) superconducting layers.