Broadband electric spectroscopy: a powerful tool for the determination of charge transfer mechanisms in ion conductors

Ionically conducting materials (ICMs) are of great importance for the fabrication of portable batteries for electronic devices such as computers, tools, video and still cameras, and for the development of fuel cell and battery-powered electric vehicles, dye-sensitized solar cells, supercapacitors, and sensors. It has been suggested that conductivity in ICMs occurs via a number of different processes. The predominant conductivity processes are attributed to: (a) the migration of ions between coordination sites in the host materials, and (b) the increase of conductivity due to relaxation phenomena involving the dynamics of the host materials. Ions hopping to new chemical environments can lead to successful charge migration only if ion-occupying domains relax via reorganizational processes, which in general are coupled with relaxation events associated with the host matrix. In this work, the instruments used in the comprehensive study of the electric response of ICMs are described, and the basic tools to understand broadband electric spectroscopy are provided. The first part of the presentation reviews the general phenomena and the basic theory underlying each type of electric response that materials may exhibit when they are subjected to static or dynamic electric fields. Afterwards, the strategies of data analysis, which is accomplished using specific empirical or theoretical models, are described in detail. The final part of the presentation discusses the methodologies for accurate data collection.