Enhanced interionic forces above Tc in ABX3-type superionic conductors Original Research Article

In order to investigate interionic forces in ABX3-type superionic conductors, we measure far-infrared reflectivity spectra of CsPbCl3 in the temperature range from 40 to 381 K. Four phonon bands are observed in the low temperature region, and a contribution of the fourth order anharmonicity to the phonon damping constant is suggested. A rapid increase and decrease in bindings between the frame ions, and between the mobile and frame ions at Tc, respectively, are suggested from the long-range force fL, and short-range force fS, that are estimated from the two high frequency bands in CsPbCl3 and in Ag3SX (X=Br, I), using the point charge model. These forces are related to several relationships for the ion conduction.