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Synthesis of Celsian (BaAl 2 Si 2 O 8 ) from Solid Ba‐Al‐Al 2 O 3 ‐SiO 2 Precursors: I, XRD and SEM/EDX Analyses of Phase Evolution
Author(s) -
Allameh Seyed M.,
Sandhage Kenneth H.
Publication year - 1997
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1997.tb03239.x
Subject(s) - monoclinic crystal system , materials science , silicate , phase (matter) , barium , x ray crystallography , crystallography , analytical chemistry (journal) , mineralogy , hexagonal crystal system , diffraction , chemistry , crystal structure , metallurgy , optics , organic chemistry , chromatography , physics
An intimate Ba‐Al‐Al 2 O 3 ‐SiO 2 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 BaAl 2 Si 2 O 8 . Barium oxidation was completed, and a binary silicate compound, Ba 2 SiO 4 , had formed within 24 h at 300°C. After 72 h at 650°C, aluminum oxidation was completed, and an appreciable amount of BaAl 2 O 4 had formed. Diffraction peaks consistent with hexagonal BaAl 2 Si 2 O 8 , BaAl 2 O 4 , β‐BaSiO 3 , and possibly β‐BaSi 2 O 5 were detected after 24 h at 900°C. Diffraction peaks for BaAl 2 O 4 and BaAl 2 Si 2 O 8 were observed after 35 h at 1200°C, although SEM analyses also revealed fine silicate particles. Further reaction of this silicate with BaAl 2 O 4 at 1350° to 1650°C yielded a mixture of hexagonal and monoclinic BaAl 2 Si 2 O 8 . The observed reaction path was compared to prior work with other inorganic precursors to BaAl 2 Si 2 O 8 .