## 1 Introduction
For transient measurements, a step voltage function, \(v(t)\), is applied (such as \(v(t)=0\) V for \(t<0\) s, while \(v(t)=V_{0}\)\(V\) for \(t\geq 0\) s), and the respective resulting time-variant current response, \(i(t)\), is measured [14; 15]. The quotient between \(v(t)\) and \(i(t)\) is the time-varying resistance, and allows for the material's impedance due to the step voltage perturbation at the interface to be determined. A second type of stimulus consists of applying a random white noise signal to the interface, followed by measuring the resulting current [16]. The third and most common form of use is the one in which the impedance is directly measured by applying a single-frequency voltage sinusoidal signal to the interface, after which the resulting current amplitude and phase shift are measured for that same frequency (or their respective real and imaginary parts) [17; 18]. When, instead of evaluating the response to a single frequency stimulus, a chosen set of frequencies is examined, a sweep, the obtained set of impedances, can be represented in the form of a Nyquist plot (the imaginary part of the impedance as a function of the real part of the impedance), or of Bode plots (the imaginary part of the impedance as a function of frequency, and the real part of the impedance as a function of frequency). A three- or two/four-points measuring configuration can be used, depending on the intended characterization. The configuration with three electrodes results in the designation in the literature of Electrochemical Impedance Spectroscopy (EIS). Specifically, a common electrode (the designated reference electrode) is used both for the excitation and measuring procedures, a counter electrode for applying the excitation signal to the media under evaluation, and a working electrode to measure the media electrical response. Measurements via the two electrodes configuration option refer to the literature-described approach of Electrical Impedance Spectroscopy (EleIS). In this case, the same pair of electrodes is used simultaneously for applying the excitation to the media intended to be analyzed and for measuring its electrical response; the four-points configuration is an extension of this approach and intended to diminish the measuring electronics setup impedance, and consequently its influence on the impedance measurements. However, independently of the measuring strategy used, measured complex data integrity must be assured (the real and imaginary components of the assessed complex impedance must have finite values over the entire evaluated frequency range). That is achieved using the Kramers-Kronig relations [19] (named in honor of [PERSON] and [PERSON] [20; 21]). They can detect errors in the impedance spectrum of a system through data integration over the entire frequency range. However, Kramers-Kronig relations evaluation requires integration over a wide range of frequencies (from zero to infinity): since no one can measure spectral data over that range, the assessment always involves assumptions about the behavior of the spectrum outside the measured frequency range. In practice, the analysis is performed by fitting a generalized model to the complex data: for instance, [PERSON] et al. [22] proposed a serial association between a resistor and several R/C circuit elements (elements composed by a resistor connected in parallel with a capacitor), while [PERSON] [23] proposed achieving it by fitting a set of linear equations, eliminating possible non-convergence issues. Presently almost all impedance analyzers that display the capacity of fitting obtained data by equivalent circuits (or software tools that perform the same procedure), possess in-built Kramers-Kronig evaluation, so the researchers' task is facilitated.