Study on Fabrication of High Strength Ceramics with Intra-and Intergranular Microstructure.

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Fundamental studies on fabrication of high strength ceramics with intragranular and intergranular microstructure were investigated in ceramics/ceramics composites of tetragonal zirconia/cubic zirconia, alumina/zirconia, silicon carbide/zirconia, beta-wollastonite/zirconia, alpha-wollastonite/zirconia and zirconia/alumina systems. These composites were fabricated by normal sintering reaction and post hotisostatic pressure sintering reaction methods. In the systems of 4 mol% and 5mol% Y_2O_3 doped zirconia ceramics, tetragonal zirconia dispersed cubic zirconia composites with high strength and high ionic conductivity were fabricated, which was first materials of the functional ceramics with excellent mechanical properties. In the composites of 8mol% Y_2O_3 doped zirconia/alumina, nanosize alumina grains were dispersed within large cubic zirconia grains, which was intra-and intergranular microstructural composites with high strength. Mechanical and thermal properties of beta-and alpha-wollastonite ceramics were improved by dispersion of monoclinic and tetragonal zirconia grains at grain boundaries. By dispersion of 12mol% ceria doped tetragonal zirconia into beta-wollastonite, thermal stability of beta-phase was improved about 100ﾟC from 1100ﾟC to 1200ﾟC. Mechanical properties of fracture strength and fracture toughness in alumina ceramics were improved by dispersion of tetragonal zirconia grains into alumina matrix. These present results indicated that the intra-and intergranular microstructural ceramics was exellent ceramic composites with high strength and functional properties.