HRTEM and Micro-Raman Studies on Superconducting−Superionic Conducting Nanohybrid, Ag1.17I1.54Bi2Sr2CaCu2Oy

The crystal structure of the superconducting−superionic conducting nanohybrid, Ag 1.17 I 1.54 Bi 2 Sr 2 CaCu 2 O y, 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 AgI 4 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 IBi 2 Sr 2 CaCu 2 O y . 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.