Equivalent circuit brick layer model

Case (i). For <7, Ogt, the brick layer model is equivalent to the series layer model but with a one-third weighting of the grain boundary resistance. This reflects the fact that grain boundaries in only one of the three orientations (i.e. normal to the current) have a blocking effect. The circuit equivalent of the brick layer model is, therefore, that of Figure 4.1.1 with parameters... 

Under the assumption of a brick layer model and serial equivalent circuit, can be calculated by the following equation [8]... 

Fig. 7.49 The equivalent circuit of the brick layer model . The validity is dependent on the local behaviour of the intersections of the grain boundaries. The approximation used in what follows refers to the broken connecting line. Then the highly conducting grain boundary paths (e.g. space charge zones) are blocked by the perpendicular boundary (e.g. core region). The factors 4 and 1/2 refer to the number of grain boundary contributions per grain (4 parallel and 2 serial half grain boundaries) according to Ref. [256].

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