Grain boundary resistance

Fig. 6. Impedance spectra in the Z plane and in the Bode plot (log(Z) vs. log(cu)) for (a) one RC element (b) two RC elements (c) three RC elements representing the situation of a polycrystal with non-ohmic electrodes and highly resistive grain boundaries and (d) three RC elements with two similar relaxation frequencies (cor2 — 3ror3) leading to overlapping semicircles.

Spatially Varying Properties of Highly Resistive Grain Boundaries... 

A quantitative interpretation of grain boundary contributions to the overall impedance of polycrystals with highly resistive grain boundaries can be problematic (see... 

In the following, four examples of quantitative microelectrode measurements are discussed in more detail. Each reflects a typical field of solid state ionics (nonstoichiometry, highly resistive grain boundaries, highly conductive interface, electrode reactions) and thus provides evidence for the vast potential of microelectrodes in solid state electrochemistry. 

This results in the formation of more conductive paths as well as reducing the number of high resistance grain boundaries. This explanation is supported by scanning electron microscope (SEM) pictures. After the extended grain connections are formed and the sample is subsequently cooled, the sample retains its high conductivity (comparable to a dirty metal). 

Fig. 10.14. This HREM image of a resistive grain boundary shows structural disorder within an approximately 10 A wide region at the grain boundary...

Eleig, /., and Maier, J. (1999). Einite-element calculations on the impedance of electroceramics with highly resistive grain boundaries 1. Laterally inhomogeneous grain boundaries. /. Am. Ceram Soc. 82 3485-3493. 

Fig. 16 Equi-potential contour maps of (a) single crystal and (b) polycrystalline materials with highly resistive grain boundary pgb =100/9g, 5gb=0.02<7g). The changes of line and color indicate equi-potential lines. Potential drop between two neighboring lines is 1/20 of the applied voltage, according to [67].

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