Microstructural Control During Sintering of β″-Alumina Compositions Through Ceramic Processing Modification
The exaggerated grain growth during high temperature (1585° – 1600°C) sintering of Li2O-stabilized β″-alumina compositions is essentially a process or very rapid growth of stabilized 3″ nuclei to large dimensions (>100 µm) while the matrix remains extremely fine-grained (< 3 µm). The final grain size is therefore inversely proportional to the cube root of the volume fraction originally occupied by these nuclei~1 Such a relationship was reported by Cutler in the case of seeded alpha alumina powders and more recently by Lacour and Paulus3 in the case of barrium-hexaferrite. The occurrence of an exaggerated grain growth during sintering of ceramics has been shown to depend on the flux-growth mechanism wherein a film or channel of liquid phase surrounds the growing nuclei. The growth of nuclei to large dimensions takes place by the solution of surrounding fine grains in the liquid and their precipitation on the growing crystal surface. While Cooy4 and Stuijts5 reported accidental impurities as the cause of liquid phase formation, Lacour and Paulus3 showed that local inhomogenities can also give rise to a liquid phase responsible for the flux growth.
KeywordsGrain Size Distribution Flux Growth Microstructural Control Lithium Salt Size Distribution Histogram
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