Synthesis of Celsian (BaAl2Si2O8) from Solid Ba-Al-Al2O3-SiO2 Precursors: I, XRD and SEM/EDX Analyses of Phase Evolution |
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Authors: | Seyed M Allameh Kenneth H Sandhage |
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Affiliation: | Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 |
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Abstract: | An intimate Ba-Al-Al2O3-SiO2 powder mixture, produced by high-energy milling, was pressed to 3 mm thick cylinders (10 mm diameter) and hexagonal plates (6 mm edge-to-edge width). Heat treatments conducted from 300° to 1650°C in pure oxygen or air were used to transform these solid-metal/oxide precursors into BaAl2Si2O8. Barium oxidation was completed, and a binary silicate compound, Ba2SiO4, had formed within 24 h at 300°C. After 72 h at 650°C, aluminum oxidation was completed, and an appreciable amount of BaAl2O4 had formed. Diffraction peaks consistent with hexagonal BaAl2Si2O8, BaAl2O4, β-BaSiO3, and possibly β-BaSi2O5 were detected after 24 h at 900°C. Diffraction peaks for BaAl2O4 and BaAl2Si2O8 were observed after 35 h at 1200°C, although SEM analyses also revealed fine silicate particles. Further reaction of this silicate with BaAl2O4 at 1350° to 1650°C yielded a mixture of hexagonal and monoclinic BaAl2Si2O8. The observed reaction path was compared to prior work with other inorganic precursors to BaAl2Si2O8. |
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