Crystal, charge-carrying species

KNs. The d.c. electrical conduction of KN3 in aqueous-solution-grown crystals and pressed pellets was studied by Maycock and Pai Verneker [127]. The room-temperature conductivity was found to be approximately 10" (ohm cm) in the pure material. Numerical values for the enthalpies of migration and defect formation were calculated from ionic measurements to be 0.79 0.05 and 1.43 0.05 eV (76 and 138 kJ/mole), respectively. In a subsequent paper [128], the results were revised slightly and the fractional number of defects, the cation vacancy mobility, and the equilibrium constant for the association reaction were calculated. The incorporation of divalent barium ions in the lattice was found to enhance the conductivity in the low-temperature region. Assuming the effect of the divalent cation was to increase the number of cation vacancies, the authors concluded that the charge-carrying species is the cation, and the diffusion occurs by means of a vacancy mechanism. 

The polymerization of A -vinyl carbazole may be initiated by free radicals, by cations, by organometallic catalysts, by charge-transfer processes, or by electrochemical methods. Since the monomer is a solid at room temperature (m.p. 64-66°C, b.p. 154-155°C/3 mm), solid state polymerizations have been carried out both on powdered monomer and on the surfaces of larger crystals. In this process, the reactive species propagates into the interior of the solid. 

Sodium chloride is an ionic compound, consisting of Na and Cl ions. When NaCl is dissolved in water, these ions are set free and can move independently to conduct the electric current. Sugar crystals, although they may appear similar visuahy, contain no ions. When sugar is dissolved in water, it dissolves as uncharged molecules. No electrically charged species are present in a sugar solution to carry the electric current. 

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