Journal of Physical Chemistry B, Vol.104, No.39, 9086-9090, 2000
HRTEM and micro-Raman studies on superconducting-superionic conducting nanohybrid, Ag1.17I1.54Bi2Sr2CaCu2Oy
The crystal structure of the superconducting-superionic conducting nanohybrid, Ag1.17I1.54Bi2Sr2CaCu2Oy, has been investigated by performing high-resolution transmission electron microscopy (HRTEM) and micro-Raman spectroscopy. From the HRTEM image along the [110] direction, it is found that a hexagonal-like array of AgI4 tetrahedra is stabilized between each [Bi-O](2) double layer with a staggered configuration of host block. The two-dimensionally extended Ag-I sublattice provides a favorable migration path for Ag+ ions 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 observed in the phase of IBi2Sr2CaCu2Oy. Such an evolution of the O-Sr phonon peak 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 HRTEM result.