Grain boundary electroconductivity

ELECTROCONDUCTIVITY OF THE BULK AND GRAIN BOUNDARIES IN THE 0.8Ce02-0.2Gd203 ELECTROLYTE PREPARED FROM NANOPOWDERS... 

Fig. 4 presents temperature dependences of the total specific resistance of some electrolytes based on cerium oxide. It is seen that the total electroconductivity of the ceramic under study is comparable with best conductivity values, which were obtained earlier for fiat samples prepared by magnetic pulse compaction (curves 6-7 in Fig. 4). Only the ceramic of the formula CeioGd, which was synthesized by Steele, had better characteristics (3, Fig. 4). His ceramic usually had a negligibly small resistance of grain boundaries.

It is commonly assumed that the main reason for the decrease in the total electroconductivity of ceramics is grain boundaries and impurities, primarily Si, localized at boundaries. Notice that although the share of grain boundaries in the material, which was synthesized from nanopowders, was very large, their contribution to the decrease in the total electroconductivity of the ceramic was insignificant. 

The bulk electroconductivity of the electrolyte grains in our material was higher than in other electrolytes (Fig. 5). Steele s data were plotted assuming a zero contribution of grain boundaries to the total resistance of the ceramic. 

After the loss due to grain boundaries in the electrolyte is minimized, probably we shall be able to produce an efficient electrolyte with a higher electroconductivity for use in intermediate-temperature SOFC s. 

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