Electrochemical Nyquist diagram

Figure 8.7 (a) Equivalent electric circuit corresponding to an oxide ion conductor and the corresponding electrochemical Nyquist diagram, (b) Example of a polycrystalline sample. 

Figure 2.37 shows an example impedance spectrum of an electrochemical system with two time constants. Figure 2.37a, b, and c are the equivalent circuit, simulated Nyquist diagram, and Bode plot, respectively. 

The measured frequency characteristics of electrochemically produced iron and S235JR steel in corrosive environment of 0.5M NaCl solution are presented in the form of Nyquist diagrams (Fig. 14) and Bode plots of impedance spectra (Fig. 15). 

Nyquist diagrams of the electrochemical impedances corresponding to a two-consecutive step anodic dissolution. Points stand for the result of Monte Carlo simulations without surface relaxation (open circles) and with surface relaxation (solid circles) for a. Number of cycles is n = 20 and V = O.lmV. Frequency values range from CO = 0.005 to co = 10 s. Continuous solid line corresponds to inductive loop behavior of Zp (ffl) predicted by Equation 3.15. Dashed line stands for an analytical approach of the rough case. (From Cdrdoba-Torres, P., Keddam, M., and Nogueira, R.P., Electrochim. Acta, 54, 518,2008. With permission.)... 

When a range of frequencies is applied to the DUT, both El and ECI techniques are called spectroscopies, i.e., electrical impedance spectroscopy and electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy (EIS) profiles, measured as a function of the interrogating frequency, can be presented by two popular plots complex plane impedance diagrams, sometimes called Nyquist or Cole-Cole plots, and Bode (I Z I and 6) plots (Fig. 2). As the impedance, Z, is composed of a real and an imaginary part, the Nyquist plot shows the relationship of the imaginary component of impedance, Z" (on the Y-axis), to the real component of the impedance, Z (on the X-axis), at each frequency. A diagonal line with a slope of 45° on a Nyquist plot represents the Warburg... 

Fig. 2 Representative (a) complex plane diagrams (Nyquist or Cole-Cole plots) and (b) Bode plots from electrochemical impedance spectroscopy measurements...

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