HRTEM and micro-Raman studies on superconducting-superionic conducting nanohybrid, Ag1.17I1.54Bi2Sr2CaCu2Oy

The crystal structure of the superconducting-superionic conducting nanohybr id, Ag1.17I1.54Bi2Sr2CaCu2Oy, has been investigated by performing high-reso lution transmission electron microscopy (HRTEM) and micro-Raman spectroscop y. From the HRTEM image along the [110] direction, it is found that a hexag onal-like array of AgI4 tetrahedra is stabilized between each [Bi-O](2) dou ble layer with a staggered configuration of host block. The two-dimensional ly extended Ag-I sublattice provides a favorable migration path for Ag+ ion s that is consistent with high ionic conductivity of the Ag-I intercalate. According to the polarized micro-Raman spectroscopy, the doubly split O-Sr phonon line is collapsed into a single one upon Ag-I intercalation, as obse rved in the phase of IBi2Sr2CaCu2Oy. Such an evolution of the O-Sr phonon p eak is surely attributed to a weakening of the O-Bi-Bi-O-Sr coupling due to the remarkable lattice expansion, which is in good agreement with the HRTE M result.