G. Groppi et al., THE CRYSTAL-STRUCTURE OF BA-BETA-ALUMINA MATERIALS FOR HIGH-TEMPERATURE CATALYTIC COMBUSTION, Journal of solid state chemistry, 114(2), 1995, pp. 326-336
Structure refinement through Rietveld analysis has been performed on a
series of Ba-Al-O samples with Al/Ba ratios in the range 9-14. This m
aterial is considered for its potential use in catalytic combustion. T
he results show that different beta-Al2O3-type structures are obtained
upon calcination at 1670 K depending on the Al/Ba ratio. A beta(II)-A
l2O3 phase forms for the lowest Al/Ba ratio and a beta(1)-Al2O3 forms
for the highest one. Small amounts of additional phases are present in
the samples with the border compositions. For an in-between compositi
on (Al/Ba = 12) a monophasic sample is obtained with crystal structure
and calculated cell parameters intermediate between those of beta(I)
and beta(II). The sample with the intermediate composition exhibits th
e highest surface area. A strict relationship between surface area and
aspect ratio of the crystallites has been observed. This indicates th
at the sintering resistance of these materials derives from the suppre
ssion of crystal growth along the crystallographic axis c. Experimenta
l data also indicate that sintering resistance is closely related to B
a content. (C) 1995 Academic Press, Inc.