The size dependent adsorption properties of ferroelectric particles

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