Cationic Short-Range Order in the Hollandite K1.54 Mg0.77 T7.23 O16: Evidence for the Importance of Ion-Ion Interactions in Superionic Conductors

Abstract

Analysis of the diffuse x-ray scattering in the one-dimensional ionic conductor ${\mathrm{K}}_{1.54}$-${\mathrm{Mg}}_{0.77}$ ${\mathrm{Ti}}_{7.23}$ ${\mathrm{O}}_{16}$ (hollandite) yields a detailed microscopic picture of the cationic shortrange order. This order is characterized by large shifts of some ions off their crystallographic sites, evidencing that in a superionic conductor the ion-ion interaction may be stronger than the periodic potential of the host crystal.