Far-infrared and incoherent neutron scattering experiments of the solid electrolyte (C5H5NH)Ag5I6

Abstract

Pyridinium pentasilver-hexaiodide, (C₅H₅NH)Ag₅I₆, is a solid electrolyte with a very high conductivity of the Ag⁺ ions, comparable to those of the best ionic conductors such as AgI and RbAg₅I₆. Far-infrared experiments (FIR) show the existence of very low frequency optical modes with h(cross) omega approximately=2-3 meV. The lack of structure in the incoherent neutron scattering experiments in this energy range strongly suggests that these low frequency modes are of prime importance for the conduction mechanism: the low frequency z polarised mode can be regarded as a 'quasi-attempt' mode for jumps of Ag⁺ ions from 4c-sites into adjacent empty 4c-sites along channels formed by face-sharing iodide octahedra.