Maximum conductivity

The investigation of ion-aggregate formation based on conductivity studies can be extended to quadruple-ion formation [108-111], which is thought to be the reason for the conductivity maximum and the subsequent decrease of conductivity. 

Recent developments of the chemical model of electrolyte solutions permit the extension of the validity range of transport equations up to high concentrations (c 1 mol L"1) and permit the representation of the conductivity maximum Knm in the framework of the mean spherical approximation (MSA) theory with the help of association constant KA and ionic distance parameter a, see Ref. [87] and the literature quoted there in. 

Sowada and Warman (1982) have described a dc conductivity method for Ar gas at 295 K and 45 atm. Following a 20-ns pulse of irradiation, the conductivity rises to a peak at -50 ns, due to the Ramsauer effect, before settling to a plateau, which is ascribed to thermal conductivity since the collecting field is very low. Since there is little electron loss, the conductivity profile is proportional to the mobility profile this in turn can be considered a kind of image of collision frequency as a function of electron energy. The time to reach the conductivity plateau, -150 ns, is the measure of thermalization time in the present case. At a density of -9 X 1021 cm-3, the conductivity maximum vanishes, indicating the disappearance of the Ramsauer minimum according to Sowada and Warman. 

HMPA gives, however, poorly conducting solutions 89 In the course of the conductometric titration of FeCl3 with HMPA in nitrobenzene a conductivity maximum is observed at a molar ratio HMPA FeCl3 = 1 2 and [FeCl4 ] ions are present at this composition of the solution. It is likely that the complex cation which is simultaneously produced by autocomplex formation may contain coordinated nitrobenzene molecules ... 

A clear example of this effect is found in the Li4 3,Al,Si04 solid solutions (Garcia, Torres-Trevino and West, 1990), scheme 1, Fig. 2.2. Single phase solid solutions form over the entire range x = 0-0.5. At X = 0, in stoichiometric Li4Si04, all the Li sites are full and the conductivity is low. As x increases, one particular set of Li sites in the crystal structure starts to empty and is completely empty at x = 0.5, i.e. at Li2.5Alo.5Si04. The effect on the ionic conductivity of this variation is dramatic, as shown in Fig. 2.3. A broad conductivity maximum occurs around x = 0.25, at which composition the mobile Li" sites are half-full (Mc = 0.5, where is the occupancy of the site by ions). To either side, the conductivity becomes very small as x 0 (n,. 1) and x -> 0.5 (tie 0) respectively. ... 

Material Doping with Conductivity Maximum Doping Stability in Air... 

If the ZnO sample was heated at 250°C in hydrogen before the measurement was made, a different curve was obtained, with the conductivity maximum at 150°C. After the sample was heated at 400°C in hydrogen (less hydrogen adsorbed, according to Taylor and Strother (44)), a curve showing two conductivity maxima, one at 25O C, and one at 150°C, is obtained. 

Iodine oxidation of Ni(OEP) and Cu(OEP) yields polycrystalline materials with a range of stoichiometries.108 Resonance Raman studies indicate the presence of I5- in contrast to the I3 observed for larger ring macrocycles. Single crystal studies of Ni(TMP)I indicate a metal-over-metal stack arrangement but with the Ni(TMP) unit puckered. The iodine superlattice is incommensurate with the Bragg lattice.107 The room temperature conductivity is 10 Q-1 cm-1 and increases on lowering the temperature to reach a rounded maximum at 115 K. The spin susceptibility is temperature independent down to a transition temperature of 28 K, well below the conductivity maximum. Below 28 K the susceptibility decreases in an activated fashion with Ajk 60 K.108... 

Operating voltage Conductivity Maximum capacity Technical, economic characteristics, and security... 

The conductivity of Ni(tmp)I at room temperature is high (o 100 Q 1cm 1) and metal-like, increasing until it reaches a rounded maximum at T 115 °K, then decreasing in an activated manner. The spin susceptibility is temperature independent down to a transition temperature of 28 °K, well below the conductivity maximum. At temperatures below the transition, the susceptibility decreases in an activated fashion, with A/k = 60 °K. Similar observations with organic conductors (TMTTF)2Y, Y = CIO4, BF4, have been attributed to a Peierls transition212, but in the present instance the mechanism has yet to be elucidated. 

From more recent optical data it is proved that Qn(TCNQ)2 is a semiconductor up to 300 K, with an energy gap due mainly to a Peierls distortion on the conducting TCNQ chains [57]. However, this gap Ec = 2A is not constant, as is simply assumed in the model of Epstein et al. In fact, A appears to decrease significantly from = 1200 K at T = 0 K to = 300 K at T = 300 K, somewhat like in the salt TEA(TCNQ)2 (see above). This requires a modified approach in which the existence of a conductivity maximum cjm still implies a T-dependent mobility p, but not so steep as would require a constant gap. 

Table 2. Selected organic metals [39]. None of these compounds superconduct. The temperature of maximum conductivity is in parentheses if it is a broad conductivity maximum...

The electrical conductivity of ceramic materials in the system Zr02 — Y2O3 is shown in Fig. 206. The diagram exliibits a conductivity maximum which also occurs with other trivalent oxides at roughly the same concentration. 

The desired results after sintering and annealing are 100% conversion to the ) " phase for maximum sodium ion conductivity maximum mass density to eliminate porosity, particularly large pores, in the microstructure uniform, fine grain size below 10 pm, to maximize strength and minimize sources or singularities for fracture and no loss of NaaO to control composition and eventually the sodium ion conductivity. 

Ioffe, A.I., Rutman, D.S., Karpachov, S.V. On the nature of the conductivity maximum in zirconia-based solid electrolytes. Electrochim. Acta 1978, 23,141-2. 

The effect of NaOH concentration and temperature on the swelling and conductivity of Nafion has been recently studied by Men shakova et The influence of NaOH concentration on the membrane conductivity is rather similar to the case of acid electrolytes in that a conductivity maximum occurs. The authors found that the conductivity maximum of the membrane is at —20% NaOH, i.e., close to the concentration where one observes the conductivity maximum of the free electrolyte. However, the conductivity decrease following the maximum is more drastic in the membranes... 

Conducting polymers like commercially available PEDOT PSS are the third class of printable conductors. However, their conductivity (maximum 500 S/ cm for PEDOT PSS [11]) is several orders of magnitude lower than the conductivity of metals. The advantages of PEDOT PSS are its transparency, flexibility and low-temperature post-processing the thermal treatment is only necessary to remove residual solvent, no sintering is required. 

The absence of an electrical conductivity maximum is troublesome. We assume that the intrinsic disorder effects arB predominant ... 

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