ADSORPTION OF CARBON-DIOXIDE BY BARIUM-TITANATE - EVIDENCE OF ADSORPTION PROCESS MEDIATED BY A DIPOLE-DIPOLE INTERACTION

This work presents desorption curves of CO2 for powder of barium titanate with main particle sizes of 1000, 500, 200, 100 and 50 micrometers in diameter. The percentage of surface area occupied by CO2 molecules is calculated after measuring the total surface area of the samples using N-2 single point BET. Adsorption of CO2 and N-2 were measured with a Quantasorb instrument using flowing helium. Nitrogen or CO2 concentration changes in the flowing mixture, during desorption, were sensed by a specially designed thermal conductivity detector. The ratio of surface area covered by CO2 with respect to N-2 changes from 50% for particle sizes between 1000 and 200 mu m down to 19% for 50 mu m particles. Spontaneous polarization measurements for samples with main particle sizes of 50 an 100 mu m were made and they show a weak ferroelectric behavior, indicating that ferroelectricity is destroyed for these small particles. A tentative explanation of these results is the assumption that the adsorption of some CO2 molecules on the ferroelectric substrate is mediated by a dipole-dipole coupling between the CO2 molecules and the substrate.