Characterisation by SEM, TEM and XPS of BaTiO3 powders that have been expos
ed to water provides an assessment of the extension of their interaction wi
th the suspending medium. Ba2+ ions are released into the aqueous solution
when powder suspensions are prepared, as detected by atomic absorption spec
troscopy, but it appears that their presence in the aqueous medium is due t
o dissolution of BaCO3 present in the powders as an impurity. No changes in
morphology of the powders or composition of the surface were observed, a p
art from precipitation of BaCl2 on the surface of the particles when the pH
was lowered with HCl. However, a similar to 20 nm layer depleted in Ba2+ d
evelops at the sup face of undoped sintered materials after exposure to wat
er, as a result of the partial hydrolysis of the BaTiO3, which affect in le
ss extent to Nb-doped sintered material. (C) 1998 Elsevier Science Limited.
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