Effect of Green Compact Pore Size Distribution on the Sintering of α-Fe2O3
The bulk electrical properties of α-Fe2O3 are very useful for many potential applications.1,2 The macroscopic properties of sintered α-Fe2O3 are due to inter- and intra-granular features which are highly dependent on the ceramic microstructure and on the presence of structural defects.3 Twinning and dislocations normally present in α-Fe2O3 ceramics influence the magnetic and electric structure. As a consequence, electronic transport associated with the varistor effect in this material is dependent on the concentration of these defects, which in turn are dependent on the morphological characteristics of the precursors and on the sintering conditions.4’5 There is no agreement on sintering mechanisms of α-Fe2O3 reported in the literature. For low temperatures between 500 and 700℃ Whittemore and Varela6 have shown large pore growth during sintering, explained by the coalescence of grains. Idzikowski7 observed a fast grain growth in this range of temperatures, suggesting a mechanism of mass transport due to different types of necks. Santilli et al8 showed that grain coalescence occurs mainly in powders derived from goethite while grain growth does not occur in compacts made from amorphous iron oxide precursors. Yamaguchi and Kosha9 studied the sintering of α-Fe2O3 with elongated and spherical particle shapes, derived from the calcining of a-FeOOH and Fe2(S04)3, respectively. They observed a fast initial densification with pore growth and grain reorientation of acicular particles. This behavior was attributed to structural rearrangement.
KeywordsStructural Rearrangement Sinter Time Compaction Pressure Pore Size Distribution Curve Pore Growth
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