MOLECULAR LAYER-BY-LAYER ENGINEERING OF SUPERCONDUCTING AND SUPERIONIC MATERIALS IN THE (AGI)BI2SR2CACU2OY SYSTEM

We have developed a new interstratified system consisting of a superconducting layer alternating with a superionic conducting one, which is the AgI intercalated Bi2Sr2CaCu2Oy With well-defined 2-dimensional heterostructure. Before and after the intercalation of AgI, the superconducting properties remained unchanged with the T-c's of 76 K for the pristine and 63 K for the intercalate. From the extended X-ray absorption fine structure spectroscopic analysis, it is found that the intercalated AgI is formed as the beta-like intracrystalline structure in the 2-dimensional interlayer space of Bi2Sr2CaCu2Oy. According to the ac impedance and de relaxation measurements, the ionic transference number (t(i) = sigma(i)/sigma(T)) has been estimated to be 0.27 (at 167 degrees C), indicating that the substantial ionic conductivity (sigma(i)) contributes to the total electrical one (sigma(T)). In comparison of the ionic conductivity for (AgI)Bi2Sr2CaCu2Oy (sigma(i) approximate to 10(-3)-10(-2.3) Omega(-1) cm(-1)) with those for the well-known superionic conductors of cation-substituted beta-aluminas, the ionic transport in (AgI)Bi2Sr2CaCu2Oy turned out to be significant, even comparable with the superionic conductors.