title: Pressure induced ionic-superionic transition in silver iodide at ambient temperature.
abstract: Silver iodide (AgI-V) is an archetypical ionic compound for studying the formation mechanism of a superionic state. Previous studies have proven that superionic AgI with high ionic conductivity greater than 0.1 Ω(-1)cm(-1) could only be obtained at high temperatures. We show in this paper that high pressure could also induce the superionic state in AgI even at ambient temperature. Using electrochemical impedance spectroscopy, we investigated Ag(+) ions diffusing in rock-salt structured AgI-III and KOH-type AgI-V under high pressures and directly observed the superionic state in AgI-V. The diffusion coefficient of AgI-V is ∼3.4 × 10(-4)-8.6 × 10(-4) cm(2)/s in the investigated pressure range of 12-17 GPa, comparable with those of superionic α-AgI and AgI-III'. By analyzing the half infinite length Warburg diffusion process, two parameters α and β, which closely relate to the disordered state of Ag(+) ions, have been determined and it was suggested that Ag(+) ions in AgI-V become disordered. The ionic conductivity of AgI-V is three orders of magnitude higher than that of AgI-III, and has reached around 0.1 Ω(-1)cm(-1). Evidence for all three, the diffusion coefficient, α and β, and conductivity have proven that AgI-V is a superionic conductor at ambient temperature.
authors: Biogeochemistry Department,Max Planck Institute for Chemistry, P.O. Box 3060, 55020 Mainz, Germany.
authors: Y H
authors: YH
authors: Han
authors: Biogeochemistry Department,Max Planck Institute for Chemistry, P.O. Box 3060, 55020 Mainz, Germany.
authors: H B
authors: HB
authors: Wang
authors: Biogeochemistry Department,Max Planck Institute for Chemistry, P.O. Box 3060, 55020 Mainz, Germany.
authors: I A
authors: IA
authors: Troyan
authors: State Key Laboratory of Superhard Materials, Jilin University, 130021 Changchun, China.
authors: C X
authors: CX
authors: Gao
authors: Biogeochemistry Department,Max Planck Institute for Chemistry, P.O. Box 3060, 55020 Mainz, Germany.
authors: M I
authors: MI
authors: Eremets
mesh_terms: D058266:Dielectric Spectroscopy; D004058:Diffusion; D007454:Iodides / Q000737:chemistry*; D007477:Ions / Q000737:chemistry*; D011312:Pressure; D012834:Silver / Q000737:chemistry; D018030:Silver Compounds / Q000737:chemistry*; D013696:Temperature
chemical_list: D007454:Iodides; D007477:Ions; D018030:Silver Compounds; D012834:Silver; C030584:silver iodide