Dependence of electrical conductivity

The temperature dependence of electrical conductivity has been used [365] to distinguish between the possible structural modifications of the Mn02 yielded by the thermal decomposition of KMn04. In studies involving additives, it is possible to investigate solid-solution formation, since plots of electrical conductivity against concentration of additive have a characteristic V-shape [366]. 

It should be noted, however, that due to slow kinetics in change of o<0 observed during adsorption of numerous acceptors one cannot rule out a possibility of detecting of a quasi-equilibrium dependence of electric conductivity on pressure in experiment. In this case (which is more characteristic for high ohmic adsorbents with large [Pg.65]

Fig 2.9. The field dependence of electric conductivity of a thin sintered film (/) and a pressed ZnO sample (2) [37]... 

The conclusion regarding the fact that constant current conductivity involves not all microcrystals of the sample is proved by results of measurements of electric conductivity in sintered ZnO films in case of alternating current (Fig. 2.10). The availability of barrier-free ohmic pathways is proved by a low value of initial resistivity in sintered samples ( 1 - 5 kOhm) in addition to exponential dependence of electric conductivity plotted as a function of inverse temperature having activation energy 0.03 - 0.5 eV, which coincides with ionization energy of shallow dope levels. The same value is obtained from measurements of the temperature dependence of the Hall constant [46]. 

The kinetic equation describing the change in concentration of conductivity electrons and consequently the time dependence of electric conductivity has the following shape... 

Fig. 6.10. The dependence of electric conductivity of the selenium film with adsorbed radicals as a function of temperature (/) at the rate of change of electric conductivity of sensor (2).

FIGURE 1.5 (a) Temperature dependence of electric conductivity (b) infrared electric conductivity of PANI-CSA. 

The second period, from 1890 to around 1920, was characterized by the idea of ionic dissociation and the equilibrium between neutral and ionic species. This model was used by Arrhenius to account for the concentration dependence of electrical conductivity and certain other properties of aqueous electrolytes. It was reinforced by the research of Van t Hoff on the colligative properties of solutions. However, the inability of ionic dissociation to explain quantitatively the properties of electrolyte solutions was soon recognized. 

Figure 5-6. Frequency dependence of electrical conductivity of Na-/ -alumina at different temperatures [U. Strom, K. L. Ngai (t98l) D. P. Almond et al. (1982)]. Calculation [K. Funke (1984)] with the following parameters v0 = 20 GHz, CAB(0) = k-800 K, CBA(0) = k- 200 K.

Table IV. Dependence of Electrical Conductivity cm Parameters of the Mechanochemical Synthesis...

Figure 3. Temperature dependences of electrical conductivities for the Na SO.-Y CSO,)o-Si09.

Fig. 14. Temperature dependence of electrical conductivity for sputtered films of perovskite-type solid solutions. From ref. [73].

Results obtained in the studies of temperature dependencies of electric conductivity of the synthesized ARS support the above assumptions. 

Below 120 K, the temperature dependence of electric conductivity of [N-CH3-Pz](TCNQ) is well approximated by a theoretical curve obtained in the frame of the simple activation energy model ... 

New very promising possibilities have opened by recently observed quantum effects in nanogranular metals described partly in Section 6. But much more detailed knowledge is needed for their use, so studies on these effects should be continued. Also, some problems known to be unsolved for a long time, such as the temperature dependence of electrical conductivity and a reason for the Hall effect, are also looking for their solution. The affect of shape distribution on magnetic, electrical, optical and relaxation processes is not clear today in detail the task appears to be too sophisticated but it should be solved at least by computer simulation. 

Figure 2. Temperature dependance of electrical conductivity for the sample irradiated at 14 kGy.

Figure 5. Temperature dependence of electrical conductivity of CuH7Li (CHs)20 in toluene...

To illustrate, solution of problems of this kind in the percolation theory, Quemada [71] cites the analysis of the dependence of electrical conductivity on concentration for a mixture of conducting and nonconducting spherical particles carried out by Fitzpatrick [80] or Clerk [81]. According to Clerk, this dependence is described by an equation similar to Eq. (66) or other similar formulas ... 

Figure 19 Dependence of electrical conductivity crM and activation energy Ea of TTF/TCNQ composites on molar fraction x of donor TTF. (From Ref. 87.)...

Figure 8 shows the temperature dependence of electrical conductivity (o) plotted as log(o/D vs. For higher measuring... 

Intense research has in recent years been devoted to noncrystalline materials. It was discovered also that the majority of semiconducting boron-rich borides display several properties that resemble those of the noncrystalline solids. Among the amorphous properties are the temperature and field dependencies of electrical conductivity at low temperature, the temperature dependence of thermal conductivity at high temperatures, and the temperature dependence of the magnetic susceptibility. In addition, the boron-rich semiconductors display crystalline properties, for example, the temperature dependence of the thermal condnctivity at low temperatures, the lattice absorption spectra and the possibility to change... 

Along with their excellent high temperature stability, polyimides also possess remarkable electrical properties. A detailed review of the electrical and optical properties of polyimides can be found in Ref. 62. Electrical properties of polyimides were primarily investigated in view of their low dielectric constants and insulating properties. Figure 14 shows the dependence of electrical conductivity of vapor deposited and... 

Figures 13 and 14 show the crystal structure and the temperature dependence of electrical conductivity measured along the one-dimensional axis, fc-axis, of TTF-TCNQ [53]. The conductivity increases with decreasing temperature down to about 60 K below which the conductivity is characterized by thermally activated nature. The metallic properties are ascertained by much experimental evidence such as optical reflectivity, spin-magnetic susceptibility, and thermopower [54]. In the insulating state similar measurements also suggest the presence of a band gap at the Fermi level. These measurements suggest the metal-insulator transition to oceur at 53 K.

Figure 21 shows temperature dependence of electrical conductivity and magnetic susceptibility of MEM(Af-methyl-iV-ethyl-morpholinium)-(TCNQ)2 [70]. At about 335 K it undergoes a metal-insulator transition accompanied by the onset of a two-fold superstructure and a temperature dependent magnetic susceptibility characteristic of localized moments. It is considered as depicted in Fig. 22(a) that a dimerized TCNQ accepts an electron localized by, for example, the Mott transition or the Wigner crystallization. The solid curve shown in Fig. 21(b) denotes the theoretical prediction for the magnetic susceptibility of a one-... 

Compare the temperature dependence of electrical conductivity of a metal with that of a typical metalloid. Explain the difference. 

Rice (1961) and Raleigh (1963) supposed that the concentration of electrons is proportional to the concentration of cations in the lower oxidation state. Such a condition is well fulfilled in metal-metal halide systems in the range of high concentrations of metal halide (when the metal is a minor component). However, in systems with comparable concentrations of both the cations, the situation is somewhat different. An electron can jump only when an electron donor has an electron acceptor in its neighborhood. The probability that such an acceptor is available is equal to the product x(Me +)-x(Me + " ). The exponential character of the temperature dependence of electrical conductivity is due to the fact that the concentration of cations in lower oxidation state increases with increasing temperature, which consequently increases the jump probability of the electron. 

Since the molar concentrations of cations in the investigated system could be calculated from density measurements performed by LiCko and Dangk (1982), the mobility of cations can be calculated. Using the multiple linear regression analysis, it was determined that for Ci = 0 the electrical conductivity is not equal to zero, but attains negative values. The dependence of electrical conductivity of cations on concentration corresponds to the equation... 

For the excess electrical conductivity of the real ternary system, the validity of the general Redlich-Kister s type equation can be proposed. For the description of the composition dependence of electrical conductivity in the ternary system, the following equation could then be used... 

Figure 7.06. Comparison of the temperature dependence of electrical conductivity T (full symbols) and the diffusion-induced part of the NSR rate, l/T Qjj ff (open symbols) vs inverse temperature for different Ge02 Li glasses. Actual Li content is listed in the Figure. (After Kanert et al., 1991).

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