ELECTRICAL FIELD ENHANCEMENT OF COMPACTION AND SUPER-PLASTIC DEFORMATION OF CERAMICS

摘要

A wide variety of ceramic materials, e.g. sialons, Al_2O_3, ZrO_2, BaTiO_3 and Bi_4Ti_3O_(12), have successfully been compacted by spark plasma sintering (SPS). Our most recent findings concerning preparation of nano-sized ferroelectric ceramics and concerning dramatically improved super-plastic performance in presence an external pulsed electric field will be briefly described. Compressive strain rates of the order of 10~(-2) s~(-1) at 1500°C for Si_3N_4-based ceramics containing less than 5 vol% inter-granular glassy phase have thus been obtained in the SPS-unit, while experiments in a hot press, i. e. in absence of an electrical field, yielded rates of the order 10~(-5) s~(-1). The ferroelectric domain structure of Bi_4Ti_3O_(12) has been tailored to yield specimens with extremely well aligned grains of the size 0.5x0.5x2.5 (μm)~3 exhibiting ferroelectric properties equal to or better than single crystal ones via directional dynamic ripening of nano-grains that in turn are exposed to a compressive stress.