Types of Electric Conductivity

Electric conductivity can be provided by any charged species assuming that there is a mechanism of transferring this species or transferring just a charge due to an electric potential difference between electrodes. 

A variety of metal and metal alloy wires and electrodes that are employed in electrochemical cells are typical electron conductors. 

A semiconductor can be used as an electrode in an electrochemical cell, but such cells will not be covered in this introductory book. 

FIGURE 3.1 Electron conductivity in metals. There are free electrons moving along the positively charged lattice ions. 

Electrically conductive polymers can also provide electric conductivity, which can be either electron conductor or ion conductor or both. We will briefly 

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For the purposes of discussion, we distinguish between two types of electric conductance metallic and electrolytic, the first being a stream of electrons, as in a copper wire, the second being a stream of ions, as in the case of a salt solution in water. In this case, positive ions will drift in the direction of the cathode, whereas negative ions will drift in the direction of the anode. 

Electrode reactions take place at the electrode—solution interface and their kinetics provide a switch between two types of electrical conductivity electronic at the electrode and ionic at the electrolyte. Unlike other heterogeneous chemical processes, they are not only thermally activated but also their rate is strongly influenced by the electrical field at the interface, the presence of solvent, and ionic species. 

Active catalyst agent. This is the constituent primarily accountable for the catalytic function and it includes metals, semiconductors and insulators. The type of electrical conductivity (mainly for convenience) classifies the active components. Both... 

Another type of electrical conductivity observed in ceramics is ionic conductivity, which often occurs appreciably at elevated temperature a widely used material exhibiting this behavior is zirconia doped with other oxides such as calcia (CaO) or yttria (Y2O3). For this material, atomic oxygen is the mobile ionic species. Doped zirconia finds widespread use as oxygen sensors, especially as part of automobile emission control systems, where the oxygen content of the exhaust gas is monitored to control the air-to-fuel ratio. Other applications of ionic conducting ceramics are as the electrolyte phases in solid-oxide fuel cells and in sodium-sulfur batteries. 

Historically, it has been convenient to catalog active components according to the type of electrical conductivity (Table 2.1). Table 2.1 is not intended to be exhaustive but to give perspective to the classification. More examples are given in Chapter 4. 

To determine the character of the contacts and the type of electric conductivity in organic dyes we use I/V characteristics in the present paper. 

Another type of electrical conductivity, called superconductivity, has been generating intense interest for more than two decades. When metals conduct at ordinary temperatures, electron flow is restricted by collisions with atoms vibrating in their lattice sites. Such restricted flow appears as resistive heating and represents a loss of energy. To conduct with no energy loss—to superconduct—requires extreme cooling to minimize atom movement. This remarkable phenomenon had been observed in metals only by cooling them to near absolute zero, which can be done only with liquid helium (bp = 4 K price = 11/L). 

Numerous other types of electrically conductive polymer composites are commercially available but are beyond the scope of this chapter. These materials are used in such applications as conductive inks [1], thermoplastic molded monolithic objects for electrostatic dissipation (ESD) [2] and electromagnetic interference (EMI) shielding applications [3], and a wide variety of other applications, including heating elements, switches, transducers, and batteries [2]. Similarly, the fabrication of conductive polymer materials via metal vapor deposition or electrodeposition onto polymer surfaces will not be discussed here. 

Electrode reactions are heterogeneous chemical processes that may involve one or more electron-transfer steps across the electrochemical double layer [1, 2]. Electrode reactions provide a switch for charge to flow between phases of different type of electrical conductivity electrodes and electrolyte [3]. Therefore, their response can be analyzed either on the basis of electrical or chemical models. The distinctive feature of reactions at electrodes is the strong dependence of both the surface concentrations and the kinetics on the electrode potential [4-10]. 

It is worth mentioning that indophenins, including both oligomers and polymers, represent a new type of electrically conducting materials. 

The polymers are air and waterstable and reached, doped with (I2 or FeCl3), values of 0.2-50 S/cm and represent a novel type of electrically conducting polymers. 

Since the 4f electrons are strongly localized and the RT2X2 systems show a metallic type of electric conductivity, the exchange interactions of 4f electrons can be described in terms of the well-known RKKY theory, which postulates the coupling between the moments via conduction electrons. 

There are different types of electric conductivity. In this course, we are mainly interested in the ionic conductivity of electrolytes (liquid or solid). 

There are three types of electrically conductive adhesives typically used in the electrical industry, e.g., isotropic conductive, anisotropic conductive, and nonconductive adhesives. 

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