Impedence spectroscopic studies

Conventional two-electrode dc measurements on ceramics only yield conductivities that are averaged over contributions of bulk, grain boundaries and electrodes. Experimental techniques are therefore required to split the total sample resistance Rtot into its individual contributions. Four-point dc measurements using different electrodes for current supply and voltage measurement can, for example, be applied to avoid the influence of electrode resistances. In 1969 Bauerle [197] showed that impedance spectroscopy (i.e. frequency-dependent ac resistance measurements) facilitates a differentiation between bulk, grain boundary and electrode resistances in doped ZrC>2 samples. Since that time, this technique has become common in the field of solid state ionics and today it is probably the most important tool for investigating electrical transport in and electrochemical properties of ionic solids. Impedance spectroscopy is also widely used in liquid electrochemistry and reviews on this technique be found in Refs. [198 201], In this section, just some basic aspects of impedance spectroscopic studies in solid state ionics are discussed. 

In experimental impedance spectroscopic studies, however, several factors may complicate the interpretation of the spectra and a few of these complications will briefly be touched upon i) If high conductivities are considered (a > 10-3 S cm-1), then the corresponding relaxation frequencies are well above the measurement range of a conventional impedance set-up (frequencies up to ca. 10 MHz). Hence, processes with high conductivites cannot be separated by conventional impedance spectroscopy. ii) The assumption of a quasi-one-dimensional current flow, which is the basis of the above presented brick layer model, is often violated [203, 211-214]. Some complications due to multi-dimensional potential distributions will be discussed in Sec. 3.2.1. iii) Highly conductive regions perpendicular to the electrodes (e.g. highly... 

A quantitative analysis of grain boundary impedances measured with macroscopic electrodes can be rather problematic if grain boundary properties vary from boundary to boundary (cf. Sec. 3.2). Hence, additional information on the distribution of grain boundary resistivities is often desired. Microelectrode measurements can yield such additional information (Sec. 4.2) and below a microcontact impedance spectroscopic study of grain boundaries in a polycrystal is exemplarily presented. The material of choice is again SrTiCE (0.2 mol % Fe-doped), which represents a model material for the technologically highly important class of perovskite-type titanates (see also above). 

Impedance spectroscopic studies of Li electrodes in polymeric electrolyte systems by many groups [388-402] have provided clear evidence that Li electrodes in polymeric electrolyte systems are covered by surface films. These grow during storage and control the electrochemical behavior of these systems. This is also true for the least reactive systems based on PEO [403],... 

L. Bousselmi, C. Fiaud, B. Tribollet, and E. Triki, "Impedance Spectroscopic Study of a Steel Electrode in Condition of Scaling and Corrosion Interphase Model," Electrochimica Acta, 44 (1999) 4357-4363. 

Guler Z., Erkoc R, and Sarac A S, Electrochemical impedance spectroscopic study of single-stranded DNA-immobilized electroactive polypyrrole-coated electrospun poly( -caprolactone) nanofibers. Materials Express 2015,5(4), 269-279. 

Ai, J., Chen, Y, Urquidi-Macdonald, M. and Macdonald, D.D. (2007) Electrochemical impedance spectroscopic study of passive zirconium. Jourtud of The Electrochemical Society, 154, C52. 

Macdonald, D.D. and Sun, A. (2006) An electrochemical impedance spectroscopic study of the passive state on AUoy-22. Electrochimica Acta, 51, 1767-1779. 

He T, Kreuer KD, Baikov YM, Maier J (1997) Impedance spectroscopic study of thermodynamics and kinetics of Gd-doped BaCeOs single crystal. Solid State Ionics 95 301-308... 

J. Mamouni and L. Yang, Interdigitated microelectrode-based microchip for electrical impedance spectroscopic study of oral cancer cells, Biomedical Microdevices, vol. 13, no. 6, pp. 1075-1088, 2011. 

J. Schefold, D. Lincot, A. Ambard, O. Kerrec, The cyclic nature of corrosion ofZr and Zr-Sn in high-temperature water (663K). A long-term in situ impedance spectroscopic study, J. Elec-tiochem. Soc., 2003,150,10, pp. B451-B461. 

The presence of permanent [Fe2S2] clusters in holo-NifU impeded spectroscopic characterization of transient clusters assembled in a NifS-mediated process. However, unambiguous evidence for NifS-directed assembly of oxidatively and reductively labile [Fe2S2] " clusters on NifU-1 was obtained using the combination of UV-visible absorption and resonance Raman spectroscopies (Yuvaniyama et al. 2000). The anaerobic reaction mixture involved NifU ferric ammonium citrate P-mercaptoethanol l-cysteine NifS in a 50 100 5000 1000 1 ratio. The presence of catalytic amounts of NifS facilitated meaningful UV-visible absorption results and monitoring the time course of cluster assembly. Although ferric ammonium citrate was used for these cluster assembly studies, control experiments... 

Impedance spectroscopic methods and ac voltammetry can also be used, as described in Section 14.3.7, to study electron-transfer kinetics in systems like those discussed here (71-73). 

Impedance spectroscopic measurements are randomly used in molten salt corrosion studies. In general, most of the impedance spectra emphasize diffusion-controlled kinetics for the active corrosion of metals in molten salts. This behavior is expected, as the activation energy for charge-transfer reactions is easily reached at higher temperatures. 

S.-H. Lee, H. M. Cheong, C. E. Tracy, R. Mascarenhas, Pitts, G. Jorgensen, and S. K. Deb [2000] Alternating Current Impedance and Raman Spectroscopic Study of Electrochromic a-WOs Films, Appl. Phys. Lett. 76, 3908-3910. 

The TG and impedance spectroscopic techniques have been applied to study the relative efifects of three t5q)es of superplasticizers on the hydration of cement. The amounts of calcium hydroxide formed were... 

Park, J.S., Choi, J.H., Woo, J.J., Moon, S.H. (2006) An electrical impedance spectroscopic (EIS) study on transport characteristics of ion-exchange membrane systems. 

Electrochemical polymerization offers particular advantages in that polymerized porphyrins can form electroactive, adherent and stable films on solid electrodes. Oxidative electropolymerization of several porphyrins and metalloporphyrins have been reported . Special focus has been placed on amino-substituted porphyrins due to the propensity of aniline to form electroactive polymers. Murray et al. reported on the electropolymerization of tetrakis(o-aminophenyl)porphyrin and several para-, ortho-, and meta-substituted tetrakis(aminophenyl)porphyrins with Co as a central metal s. They found that poly-Co(o-NH2)TPP films are effective catalysts for the electroreduction of oxygen in aqueous solution. Metalloporphyrin films on solid electrodes have been mainly characterized by voltammetry and resonsance Raman spectroscopy. The electrochemistry of ruthenium paradiethylamino substituted tetraphenylporphyrins recently have been investigated . This study reports the ac impedance and UV-visible reflectance spectroscopic studies of paradiethylamino substituted tetra-phenylporphyrin films formed via an oxidative electropolymerization process. 

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