Ionic conduction jump distance

The term Oq now contains n and ze as well as the information on attempt frequency and jump distance. This expression accounts for the fact that ionic conductivity increases with temperature. 

Ionic Transport, a. Conductivity The specific conductance of the SPS (Na+ form) membranes is shown in Fig. 8, whose data are summarized in Table II, including values of an apparent energy of activation. An exponential increase in ionic conductance together with a decrease in an apparent energy of activation may be related to a decrease in a "jump" distance between ion-exchange sites as a function of lEC. 

The ionic transport in solids is attributed to the hopping of ionic carriers between the equivalent positions in the crystal lattice. This mechanism is known as lattice diffusion and depends on the jumping distance and frequency of moved ions. The understanding of the influence of these factors on the ionic conductivity is very important for the development of material with enhanced ionic transport. The question of what is the limit of ionic conductivity in solids will be addressed by analyzing the ionic transport in cubic stabilized zirconia systems with different acceptor dopants. 

If both ionic conductivity and ionic diffusion occur by the same random-walk mechanism, a relationship between the self-diffusion coefficient, D, and the ionic conductivity, cr, can be derived. In the simplest case, assume that processes involve the same energy barrier, E, and jump distance, a (Figures 7.12 and 7.15). Further, if the diffusion is restricted to only one direction, the +x direction, and each jump is allowed, the diffusion coefficient is... 

Lithium-doped BPO4, another candidate ceramic electrolyte material for lithium batteries has been studied by Li NMR relaxation and linewidth measurements of samples with Li doping levels up to 20 mol % (Dodd et al. 2000). Comparison of the NMR data with values of the second moment calculated for both random and homogeneous models of Li distribution indicate the existence of Li clusters with an intemuclear distance of 3A, possibly consisting of 1 Li ion fixed at a boron vacancy with additional 2 Li ions in the conduction channels surrounding the vacancy. The atomic jump time, determined from measurements of the Li motional narrowing behaviour, indicate a maximum in the Li ionic mobility at the 10 mol % doping level (Dodd et al. 2000). 

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