çaliş açikbaş, nurcan bilecik şeyh edebali university - department of metallurgical and materials science engineering, Bilecik, Turkey , mandal, hasan sabancı university - department of materials science and nanoengineering, İstanbul, Turkey

THE FLUORINE EFFECT ON THE GRAIN-GROWTH OF 1:β1-SiAlON CERAMICS

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SiAlON ceramics are of major interest for industrial applications due to their excellent mechanical properties. The starting Si3N4 powder (α or β), the type of sintering additive and sintering conditions govern the microstructural evolution of SiAlON ceramics. In this study, α^ı:β^ı SiAlON ceramics with an equal mole intergranular phase content, different type cation systems (Y:Sm:Ca and Ca:Ce) with different molar ratio (30:64:6 and 33:67) were produced by using coarse (d50=1 μm) β-Si3N4 powder. CaF2 and CaCO3 were utilized as Ca sources. Despite the fact that αı-SiAlON phase cannot be stabilized in Ca:Ce (CaCO3 as a Ca source) system, α^1-SiAlON phase stability and unpredictable α^1-SiAlON grain-growth in both a and c directions was achieved when CaF2 was incorporated in the composition. On the other hand, an increase in α^1-SiAlON amount and more elongated SiAlON grain evolution was observed when CaF2 was used instead of CaCO3 in Y:Sm:Ca cation system. Furthermore, using CaF2 instead of CaCO3 gave rise to an increase in densities. Therefore, the substantial effect of CaF2 on abnormal grain growth and αı-SiAlON phase stabilization was observed.

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Fluorine , Grain growth , αı , SiAlON stability , Microstructure

Anadolu University Journal of Science and Technology. A : Applied Sciences and Engineering

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