The size dependent adsorption properties of ferroelectric particles

We investigated the ability of a ferroelectric oxide surface to adsorb gaseous molecules with a dipole moment or an induced dipole moment. All the ferroelectric crystals studied readily adsorb carbon dioxide, thus our studies are centered on the adsorption studies of this molecule. We describe in this paper the present status of our studies: carbon dioxide-thermal desorption curves are obtained for powders of barium titanate, potassium niobate and lithium niobate with main particle sizes of 1000, 500, 200, 100 and 50 mum in diameter. Two adsorption states an observed in these curves: a stronger state and a weaker state which appears only on the smallest particles measured (50 mum) The percentage of surface area occupied by the CO2 molecules on the ferroelectric crystals is calculated after measuring the total surface area of the samples using the N-2 single point BET method, Raman characterization as well as X-ray diffraction of the powders indicates that the dominant surface orientation of the crystallites changes when the particles become smaller than 100 mum. (C) 2001 Elsevier Science Ltd. All rights reserved.