No abstract

The distribution and orientation of platelet-shaped particlesTo develop textured ceramics by templated grain growth, it is important to choose materials which grow anisotropically. of ␣-alumina in a fine-grained alumina matrix is shown to template texture development via anisotropic grain growth.Ceramic materials with asymmetric unit cells or a crystal structure consisting of chains or layers of polyhedra often grow The textured microstructure ranges from 4 wt% oriented platelet particles in calcined samples to nearly 100% orianisotropically and have anisotropic surface energies. For example, close-packed atomic planes have low surface energy ented ␣-Al 2 O 3 grains after sintering at 1400؇C. A CaO ؉ SiO 2 liquid phase creates favorable thermodynamic and and are more thermodynamically stable. Such planes also tend to be atomically smooth, making growth perpendicular to the kinetic conditions for anisotropic grain growth and grain reorientation during sintering. Important criteria for templane difficult to nucleate. Surface energy anisotropy has been shown to be a sufficient plated grain growth include (1) anisotropic crystal structure and growth, (2) high thermodynamic driving force for temdriving force for anisotropic grain growth. Kunaver and Kolar 11 showed that grains with anisotropic surface energies grow plate grain growth, and (3) modification of diffusion in the system to continuously provide material to the anisotropianisotropically in a matrix of isotropic grains. Yang et al. 12 related the surface energy of grains in an equiaxed matrix to a cally growing template grains.theoretical anisotropic Wulff plot, and demonstrated that faceted, anisotropic grains develop.

Texture measurements were performed on liquid-phasesintered alumina textured by a templated grain growth process from 1250°to 1650°C. Texture distributions were measured using X-ray pole figures, rocking curves, Rietveld refinement, and stereology. The March-Dollase equation fitted the measured distributions very well and gave quantitative values of the degree of texture and the texture fraction. The fitting parameters of the X-ray diffraction measurements were comparable to those measured by stereology. Rocking curve analysis was found to be straightforward and to give accurate characterization of texture in the alumina system of this study in a relatively short time.