A new high-Tc superconducting intercalation compound

A new high-Tc superconducting intercalation compound, AgIBi2Sr2CaCu2Oy, has been prepared either by reacting the silver metal directly with Bi2Sr2CaCu2Oy powders under P(I2) ∼ 1atm. at 190°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 Å upon silver iodide intercalation indicates that the lattice expansion for AgIBi2Sr2CaCu2Oy is twice as large as that for the first-staged iodine-intercalated Bi2Sr2CaCu2Oy (Δd = 3.6Å). Such a result suggests the gallery contains a double layer of iodine. A slight decrease in Tc for the AgIBi2Sr2CaCu2Oy (Tc ≈ 63K) compared to the pristine (Tc ≈ 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 Tc 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.