Metastable phase relations and europium(II) luminescence of barium hexa-aluminates prepared by gel to crystallite conversion

Kutty, TRN and Nayak, M (1995) Metastable phase relations and europium(II) luminescence of barium hexa-aluminates prepared by gel to crystallite conversion. In: Materials Research Bulletin, 30 (3). pp. 325-333.

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Abstract

Wet chemical reaction of hydrated alumina gels, Al2O3.yH(2)O(80<y<120) with Ba(OH)(2) gives rise to crystallites of the precursor, Ba1+xAl12O19+x-z/2(OH)(z).nH(2)O where -0.2<x<0.32, 15<z<20 and 5<n<9. Thermal decomposition of the precursor above 1150 degrees C produces monophasic hexa-aluminate, Ba1+xAl12O19+x. Metastability of this nonstoichiometric phase is evident from the splitting of (00l) reflections, on heat treatment above 1600 degrees C, indicating the subsolidus decomposition to 0.82BaO 6Al(2)O3 and 1.32BaO 6Al(2)O(3). High resolution electron microscopy reveals extensive distribution of the blocking defects and structural intergrowths. The metastable Ba-hexa-aluminates doped with Eu(II), exhibit predominantly the 436nm emission band for all the 'x' values. No deterioration in emission intensity is noticed on long term preservation of the phosphors. Differences prevailing in literature on the phase relations in Ba-hexa-aluminates can be attributed to preparative route dependent metastability.

Item Type:	Journal Article
Publication:	Materials Research Bulletin
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	01 Jun 2011 06:10
Last Modified:	01 Jun 2011 06:10
URI:	http://eprints.iisc.ac.in/id/eprint/38099

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