SURFACE CHARACTERIZATION OF BA-BETA-ALUMINA

The surface properties of a Ba-beta-alumina sample (Ba : Al ratio 1 : 12) very stable to sintering (15 m(2)/g after calcination at 1670 K fo r 10 h) have been investigated by FT-IR spectroscopy of adsorbed probe molecules (water, pyridine and CO2) and by measuring the isoelectric point. The surface has a medium-strong basic character,justified by th e preferential exposition of Ba-O-containing ''mirror planes'', parall el to 0001 planes, on the surface of plate-like particles. This behavi or has been associated to the resistance to sintering, typical of this material, possibly originated by the difficulty of the very big Ba2ions to migrate into the spinel-type alumina blocks. This should imply the blocking of the crystal growth along the crystallographic c axis.