Effects of pore structure in green compact on the microstructure of sintered electronic ceramics

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1. Pore structure and sintering behavior of alumina compacts were examined. The green compacts were made by slipcasting of suspensions with different pH. An increase in agglomerate size in the suspension increased pore volume and size in the green compact and reduced densification rate. The microstructure development was almost the same, irrespective of pore volume and size of the green compact.2. Monodispersed polymer particles were added to alumina powder and sintered to examine densification behavior of large pores. Pores less than 1 m in diameter shrank with a considerable rate and their shape changed from spherical to lenticular. Pores more than 2 <micr>m in diameter shrank slowly and their shape was maintained. The critical pore size for the alumina powder used in this experiment was about 1 <micr>m.3. Sintering behavior of pressed and extruded acicular NiZn-ferrite and iron oxide was examined. Anisotropic shrinkage was observed. Acicular particles changed to equiaxed ones upon heating but anisotropic pore structure was maintained until the intermediate stage of sintering. Grain orientation was observed for iron oxide during the final stage of sintering.