Investigation of Sliding Friction on the Ferroic Crystals Surface

Abstract

The aim of the present work was to determine the surface structure of some ferroic single crystals as TriGlycine Sulphate (TGS), K3Na(SeO4)2 (KNSe), K4LiH3(SO4)4 (KLHS) and NH4LiH3(SO4)4 (ALHS), and to compare it with bulk structural data. Investigation of the surface structure of ferroic crystals are interesting because of some expectations that the surface structure can be correlated with the domain and/or domain boundary structures [1]. Finally, there are reports that anisotropy of sliding friction on this type of materials can originate from the different arrangement of the molecules at the surface of these crystals [1]. Until recently, the studies of the surface structures of nonconducting solids were difficult to carry out. In recent years, however, the development of new experimental tools as scanning force microscope (SFM) enabled the investigation of the non-conducting materials surface down to the atomic dimension scale [2]. Boron nitride was the first insulator that showed atomic corrugation [3]. Afterwards, the atomic structures on the sodium chloride and lithium fluoride ionic crystals have been observed [4]. There are also predictions that so-called “pre-transition” molecular re-orientation processes should be observed. We expect, that even for these crystals which never have been cooled down below the phase transition temperature (TC), the molecular orientation may reflect the orientation of the domain structure which will appear below TC.