Ionic conductivity measurements

The ratio of the tracer diffusion coefficient to the diffusion coefficient obtained from ionic conductivity measurements is called ... 

Let us imagine, for instance, that we measured the defect population of a generic oxide MO composed essentially of Schottky defects (such a measure could be obtained, for instance, by thermogravimetry at various T and Po conditions or by electronic and ionic conductivity measurements at various values of T and Pq2)- then write... 

DETA has been gaining popularity as a method for cure monitoring, and it can be used to examine the cure of elastomers via ionic conductivity measurements. Ionic conductivity is related to e" by the following equation ... 

While Dq directly reflects the ionic conductivity measured in a steady state experiment, the relationships are more complex for chemical diffusion and tracer diffusion. For simplicity we assume that the transport is so slow that local relaxation effects occur instantaneously.240... 

The Rb based on the sample cannot be calculated correctly, since the electric charge transfer resistance and the electric double layer in an electrode interface are also detected as a resistance, even if bias voltage is impressed to the measurement cell in order to measure the ionic conductivity. For the ionic conductivity measurement, a dc four-probe method, or the complex-impedance method, is used to separate sample bulk and electrode interface [4]. In particular, the complex-impedance method has the advantage that it can be performed with both nonblocking electrodes (the same element for carrier ion and metal M) and blocking electrodes (usually platinum and stainless steel were used where charge cannot be transferred between the electrode and carrier ions). The two-probe cell, where the sample is sandwiched between two pohshed and washed parallel flat electrodes, is used in the ionic conductivity measurement by complex-impedance method as shown in Figure 6.1. 

Figure 6.1 Schematic representation of cells used for ionic conductivity measurement by impedance method as an exampie. (a) Solid-state samples (b) liquid-state samples.

The hysteresis that may appear depends on the direction or the scan rate of temperature change. This tendency is based on the phase transition or slow diffusion process of sample. Remarkably such hysteresis can even appear where a sample shows crystallization within the measurement temperature range. Therefore the ionic conductivity measurement is usually performed at each temperature after reaching the constant value. On the other hand, ionic conductivity is measured at scan rate of 1° to 2° C min. Therefore, when hysteresis appears during the heating or cooling process, the relationship between the phase transition and the ionic conductivity can be used in the analysis at this scan rate with the DSC measurement. It is better to use a small cell design to avoid the temperature distribution in samples. 

The limits of integration are the oxygen partial pressures maintained at the gas phase boundaries. Equation (10.10) has general validity for mixed conductors. To carry the derivation further, one needs to consider the defect chemistry of a specific material system. When electronic conductivity prevails, Eqs. (10.9) and (10.10) can be recast through the use of the Nemst-Einstein equation in a form that includes the oxygen self-diffusion coefficient Dg, which is accessible from ionic conductivity measurements. This is further exemplified for perovskite-type oxides in Section 10.6.4, assuming a vacancy diffusion mechcinism to hold in these materials. 

Here Hr is the Haven ratio, defined as the ratio of the tracer diffusion coefficient D to the quantity D derived from dc ionic conductivity measurements. 

As discussed in previous work by the present authors [41], calculations of L<. using combined data from ionic conductivity measurements and iso-... 

For jumps involving single point defects, is accurately known for the different crystal structures. Ionic conductivity measurements, coupled with other diffusion measurements, have proved to represent a very powerful method for identifying diffusion mechanisms. However, the requirement for single-crystal samples proved to be very restrictive in terms of the materials that could be investigated, and the approach has been used successfully only for very simple systems. Examples include the combination of conductivity and diffusion in the study of alkali and silver halides [226], and the combination of conductivity and NMR in the study of barium fluoride [219]. 

The polymers were characterized from elemental analyses, TGA, IR, UV-vis spectroscopy, and ionic conductivity measurements in solution. Polymer 95 was also characterized from X-ray crystallography. 

Frenkel defects and impurity ions can diffuse through the silver halide lattice by a number of mechanisms. Silver ions can diffuse by a vacancy mechanism or by replacement processes such as collinear or noncollinear interstitialcy jump mechanisms [18]. The collinear interstitial mechanism is one in which an interstitial silver ion moves in a [111] direction, forcing an adjacent lattice silver ion into an interstitial position and replacing it The enthalpies and entropies derived from temperature-dependent ionic conductivity measurements for these processes are included in Table 4. The collinear interstitial mechanism is the most facile process at room temperature, but the other mechanisms are thought to contribute at higher temperatures. 

NaNs. Torkar and Herzog [130] determined the diffusion coefficients along the principal crystallographic axes in NaN3 from ionic conductivity measurements. They found = 10-0 = 3.3 X 10" exp (0.87 0.04 eV/... 

A recent study of potassium diffusion in KN3 indicates that cation vacancies induced by impurities dominate the diffusion process [217]. Ionic conductivity measurements also indicate that cation vacancies are responsible for the ionic current [218,219]. 

Ionic conductivity measurement permits the determination of plasticizer accumulation on the surface of plasticized PVC. A highly resistive layer of exuded plasticizer is formed on the surface of the electrode. 

Y. Aihara, T. Bando, H. Nakagawa, H. Yoshida, K. Hayamizu, E. Akiba, W. S. Price, J. Electrochem. Soc. 2004,151, A119-A122. Ion transport properhes of six hthium salts dissolved in y-butyrolactone studied by self-diffusion and ionic conductivity measurements. 

Hayamizu, K. Aihara, Y. Aral, S. Martinez, C. G., Pulse-Gradient Spin-Echo H-1, Li-7, and F-19 Nmr Diffusion and Ionic Conductivity Measurements of 14 Organic Electrolytes Containing LiN(S02CF3)2. J. Phys. Chem. B 1999,103, 519-524. 

Conductivity measurements have been carried out on powder samples of NaEu2Cl6 by means of impedance spectroscopy (fig. 12). The activation energy for the conduction process was calculated to 0.23 eV The value fits into the range one would expect for semiconductors on the other hand, there should be contributions of the Na ions to the overall conductivity. With the partial filling of the sodium sites and the channel along the c-axis the structure certainly fiilfills the requirements for ionic conduction. Measurements on powder pellets of NaSrEuClg and AgSrEuClg indeed proved ionic motion but the... 

Mani, T., and Stevens, J. R., Transparent and adhesive polymer electrolyte for smart windows. Synthesis, characterization and ionic conductivity measurements, Polymer, 33, 834-837 (1992). 

The physical and electrochemical properties of a new class of hthium ion conducting polymer electrolytes formed by dispersing nanosized C CPO ) in the poly (vinyhdene fluoride-hexafluoro propylene) (PVDF-HFP) - LiClO complexes have been reported. The prepared membranes were subjected to XRD, SEM, TG-DTA, and FT-IR analysis. Ionic conductivity measurements have been made as a function of temperature and hthium salt concentrations. The polymeric film with a ratio of PVDF-HFP Ca3(PO )2 LiC10 75 15 10 offered maximum ionic conductivity. The interfacial property of Li/NCPE was also analyzed. The interaction that exists between the polymer and lithium salt species has been confirmed by FT-IR analysis. 

Figure 10. Figure (a) shows the Arrhenius diagram for the inition time obtained from ionic conductivity measurements for the epoxy formulation cured at dlffo-ent temperatures. Figure (b) shows the Arrhenius diagram for the maximum rate of change of log ionic conductivity for the epoxy formulation cured at different temperatures. 

Watanabe reported on the concept of ionicity, which is a ratio between the ionic conductivity measured and that deduced from NMR diffteion coefficient data (that accounts for total mobility of ions, even in the form of associated pairs or clusters that do not contribute to charge transport). Ionicity is less than unity if potential charge carriers are not available for transport, and thus reflects the degree of ionic association in the liquid. Transport properties such as viscosity, diffusion coefficient and ionicity do not vary monotonically as the alltyl side chain increases, which is consistent with the appearance of nano-segregated structures at intermediate chain lengths [54]. 

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