Electrical impedance properties materials

In summary, CPs offer numerous advantages over inorganic semiconductors for thermoelectric applications because of their unique properties. However, the poor electrical transport properties have impeded their practical application as TE materials in the past. Recent studies indicate that incorporating the inorganic nanoparticle into polymer matrix is an effective way to improve the electrical transport properties of CPs, including electrical conductivity and Seebeck coefficient, while keep the thermal conductivity at low level simultaneously. Consequently, the power factors of most CP-based nanocomposites are about 2 3 orders of magnitude higher than those of conventional pure CPs and the maximum ZT value is up to 0.1 at present. 

The physical quantities describing passive electrical behavior of material in time and frequency domain are clearly distinguished. The complex, frequency-dependent impedance (impedance spectrum) exists only in the frequency domain, whereas the impulse answer is the respective property in the time domain. A single relaxation process yields a dispersion region (e.g., 3-dispersion) with a characteristic frequency (e.g., wb) in the frequency domain that corresponds to a relaxation strength and relaxation time (time constant) in the time domain. 

If a material has a pure electric resistance property, it is considered an ohmic material and has a constant resistance R largely independent of the potential applied or the current passed through. Other materials that do not comply with Ohm s law have non-linear resistances. Ideal resistors are considered to have no function in storing energy via an electric or magnetic field. However, in AC applications, this is hardly the case because an equivalent inductance or capacitance in series with the resistor element is often considered. The use of AC circuits requires the consideration of additional opposition to current flow due to electrical and magnetic fields treated as electrical reactance effects. An electrical circuit s impedance is defined by the sum effect of resistance and resistance [3]. 

Impedance Spectroscopy (IS) is an a.c. technique for electrical characterization of materials and interfaces based on impedance measurements carried out for a wide range of frequencies (10 < f(Hz) < 10 ), which can be used for the determination of the electrical properties of homogeneous (solids and liquids) or heterogeneous systems formed by a series array of layers with different electrical and/or structural properties (for example membrane/electrolyte systems), since it permits us a separate evaluation of the electrical contribution of each layer by using the impedance plots and equivalent circuits as models, where the different circuit elements are related to the structural/transport properties of the systems [40, 41). 

The high sensitivity of electrical methods to materials properties and the possibility of their application at elevated temperatures have resulted in the development of several techniques that are sensitive to the interface layer, such as impedance spectroscopy " and the... 

For coaxial cables, the following electrical properties related to the dielectric constant of the core material and the dimensions determine the quaUty of the signal impedance, capacitance, attenuation, crosstalk, and time delay and velocity of propagation. 

Modeling of High-Speed Interconnections. Modeling the electrical behavior of an interconnection involves two steps. First, the transmission line characteristics, such as the characteristic impedance, propagation constant, capacitance, resistance, dielectric conductance, and coupling parameters, must be calculated from the physical dimensions and material properties of the interconnection. In addition, structures, such as wire bonds, vias, and pins, must be represented by lumped resistance (R), inductance (L), and capacitance (C) elements. 

The impedance for the study of materials and electrochemical processes is of major importance. In principle, each property or external parameter that has an influence on the electrical conductivity of an electrochemical system can be studied by measurement of the impedance. The measured data can provide information for a pure phase, such as electrical conductivity, dielectrical constant or mobility of equilibrium concentration of charge carriers. In addition, parameters related to properties of the interface of a system can be studied in this way heterogeneous electron-transfer constants between ion and electron conductors, or capacity of the electrical double layer. In particular, measurement of the impedance is useful in those systems that cannot be studied with DC methods, e.g. because of the presence of a poor conductive surface coating. 

In the previous section we considered the conditions under which mechanical resonances would occur in a TSM resonator. In considering only the mechanical properties of the crystal, however, we neglected consideration of how these resonances would actually be excited or detected. The device uses a piezoelectric substrate material in which the electric field generated between electrodes couples to mechanical displacement. This allows electrical excitation and detection of mechanical resonances. In constructing a practical sensor, changes in resonant frequency of the device are measured electrically. The electrical characteristics of the resonator can be described in terms of an equivalent-circuit model that describes the impedance (ratio of applied voltage to current) or admittance (reciprocal of impedance) over a range of frequencies near resonance. 

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