Preparation of barium hexa-aluminate through a hydrothermal precipitation–calcination route and characterization of intermediate and final products

Mishra, D and Anand, S and Panda, R K and Das, R P (2002) Preparation of barium hexa-aluminate through a hydrothermal precipitation–calcination route and characterization of intermediate and final products. Materials Letters, 56 . pp. 873-879.

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Abstract

high surface area (f22 m2/g) micro-sized (0.3–2 A) barium hexa-aluminate powder was prepared by the calcination (at 1400 jC for 2 h) of hydrothermally prepared precursors of orthorhombic barium carbonate and boehmite. The precursors were obtained by a hydrothermal treatment (at 180 jC, for 1 h) of aqueous solutions of barium and aluminum nitrates of appropriate compositions in the presence of aqueous urea as the neutralizing precipitant. Results of XRD, TG-DTA and SEM measurements suggest the most probable reaction sequence for the preparation of barium hexa-alumnate ceramic powder as: (i) the hydrothermal precipitation of orthorhombic BaCO3 and boehmite (g-AlOOH) precursors from the aqueous Ba and Al nitrates in the presence of urea, (ii) the formation of an interim mixture of g-Al2O3, BaCO3 and Ba–h1-alumina in the temperature range of 800–1200 jC, and finally (iii) the formation of a ceramic powder corresponding to the composition BaO6Al2O3 having halumina type structure at f1400 jC. The final material did not show presence of any other crystalline phases like alumina, baria, barium mono-aluminate and tri-barium mono-aluminate phases.

Item Type:Article
Official URL/DOI:http://www.elsevier.comrlocatermatlet
Uncontrolled Keywords:Hydrothermal; Calcination; Ba–h-alumina; Barium hexa-aluminate
Divisions:Metal Extraction and Forming
ID Code:4634
Deposited By:Dr Devabrata Mishra
Deposited On:19 Jan 2012 16:25
Last Modified:19 Jan 2012 16:25
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