The Application of Impedance Spectroscopy to Characterise Electro-materials and Devices
D. C. Sinclair
1Department of Materials Science & Engineering, Mappin Street, University of Sheffield, UK
Corresponding Author: [email protected]
Impedance Spectroscopy (IS) is a readily available and versatile technique (typically scanning from mHz to MHz) to characterise the electrical properties of a wide variety materials including polar dielectrics, semi-conductors, composites, mixed ionic-electronic conductors and solid electrolytes [1-6]. In addition, its sensitivity to thin layer effects makes it an excellent tool to probe interfacial phenomena such as grain boundaries, surface layers and core-shell effects in ceramics and electrode/electrolyte phenomena in solid-state electrochemical devices such as batteries and fuel cells.
In this tutorial we will review the fundamental concepts behind this technique and then use specific examples (based on ferroelectrics, oxide-ion conductors, barrier-layer capacitors) to illustrate how to establish the electrical microstructures of electrically homogeneous and heterogeneous ceramics and how to discriminate between ionic, electronic and mixed ionic-electronic conduction. Emphasis will be given towards; (i) how to apply multi-immitance fitting of experimental data when undertaking equivalent circuit analysis; (ii) selection of appropriate electrode materials; (iii) the use of dc bias measurements to probe non-ohmic contacts and Schottky barriers; (iv) the use of variable oxygen partial pressure (pO2) measurements to establish the type(s) of conduction carrier (i.e. n, p or ions (eg O2-). Selected examples (time permitting) of using IS to characterise devices such as multi-layer ceramic capacitors, Li-batteries and solid oxide fuel cells will also be discussed.
In the final section, we will highlight the application (and limitations) of micro-contact impedance spectroscopy as a local-probe technique to interrogate thin films and inter- and intra-granular regions in electroceramics .
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