Desorption of carbon dioxide from small potassium niobate particles induced by the particles' ferroelectric transition

The aim of this work is to understand surface properties of ferroelectric crystals related to gas adsorption. Various ferroelectric crystals involved in these studies readily adsorb carbon dioxide, thus our studies were centered on adsorption studies of this molecule. It has been claimed that a dipole moment is induced on carbon dioxide molecules that are near an oxide surface. Our experiments explored the possibility of a dipole-dipole interaction between the gas molecule and the ferroelectric oxide surface in order to explain its adsorption. We characterized the samples with scanning electron microscopy, X-ray diffraction and Raman spectroscopy. We determined the ferroelectric nature of the particles and studied the temperature-dependent phase transitions in small particles of KNbO3 using Raman spectroscopy. We were able to correlate desorption of CO2 from one surface state of KNbO3 with the occurrence of the orthorhombic to tetragonal transition in KNbO3 in particles of 1 μm size. This CO2 surface site was not observed in KTaO3, which does not show ferroelectricity at room temperature.