Grain boundary conduction

The bulk and grain boundary conductivities of a ceramic sample can be separated using the impedance, Z, by plotting ... 

The grain-boundary conductivity could be improved by the addition of small amounts of transition-metal oxides, especially at intermediate temperatures. For example,... 

FIGURE 1.18 Grain-boundary conductivity of GdjCe Cbs as a function of Gd content [85, 92],... 

FIGURE 1.23 Grain-boundary conductivity of Gd02Ce08O19 with 2% Co and sintered at 900,1100, 1300, and 1500 C. Data for a sample sintered without addition of Co is also shown for comparison [109]. 

FIGURE1.27 Composition dependence of the apparent lattice conductivity, ag, grain- boundary conductivity, a and the total conductivity, at, for SmICe1 I02 l/2 measured at 300, 400, and 500°C [115].. 

A ygb area-related excess grain boundary conductance... 

In the case of an enhanced charge carrier concentration in the space charge (cf. Fig. 4b), mainly the current parallel to the grain boundary plane is important. The corresponding parallel excess grain boundary conductance... 

Determination of the Bulk Conductivity and the Grain Boundary Conductance... 

The numerical results of Fig. 20 allow an estimate of the local grain boundary conductance at room temperature from the measured inverse resistance ratio ( ongb/ ongrain)- F°r such an estimate an inverse resistance of 8 10-12 1 / Q for the grains and of 50 10 12 1 / Q for grain boundaries, a grain size of about 25 pm, and a... 

Mechanistic Interpretation of the Grain Boundary Conductance in AgCl... 

Eq. (19) gives a solution of this integral, and hence the grain boundary conductance for enhanced silver vacancy concentration reads... 

Figure 30. Ionic space charge effects at grain boundaries in Frenkel disordered materials, (a) Theoretical profiles if u, > u .120 (b) The enhanced grain boundary conductivity can be verified by point electrode impedance spectroscopy.121 The number given are in units of nS / cm and refer to room temperature.

Figure 33. Temperature dependence of total and partial conductivities (a) in bulk and (b) at the grain boundary. Note that the values of the ionic conductivity at the grain boundary are approximate.134 (Reprinted from X. Guo, J. Fleig and J. Maier, Sepa-ration of Electronic and Ionic Contributions to the Grain Boundary Conductivity in Acceptor-Doped SrTiOj. J. Electrochem. Soc., 148, J50-J53. Copyright 2001 with permission from The Electrochemical Society, Inc.)...

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