Composition, Morphology and Mechanisms of the Formation of Oxygen-Containing Phases in Surface Heterosegregation Processes

Abstract

By X-ray microprobe analysis, X-ray phase analysis, IR spectroscopy, high resolution scanning electron microscopy, and atomic force microscopy thermally stimulated surface heterosegregation is studied in non-oxygen and oxygen-containing single crystals with the participation of oxygen. It is concluded that sodium chlorite NaClO₂ and sodium hydrocarbonate NaHCO₃ are formed on the surface of sodium chloride NaCl, gallium oxide Ga₂O₃ on the surface of gallium arsenide GaAs, titanium dioxide TiO₂ and lead oxide PbO on the surface of lead titanate PbTiO₃, the complex oxide Bi₂Ti₄O₁₁ and bismuth oxide Bi₂O₃ on the surface of bismuth titanate Bi₄Ti₃O₁₂, the complex oxides Bi₂Fe₄O₉, Bi_{26– x}Fe_xO₃₉ and bismuth oxide Bi₂O₃ on the surface of bismuth ferrite BiFeO₃, the complex oxide Pb₃GeO₅ and lead oxide PbO on the surface of lead germanate Pb₅Ge₃O₁₁. The mechanisms of the formation of surface oxygen-containing phases including the self-diffusion of matrix crystal atoms to the surface, the migration of segregated atoms on the surface, the evaporation and absorption of molecules of water, carbon oxides, hydrocarbons, oxygen, as well as the surface reactions of segregated atoms with the participation of both lattice oxygen and oxygen of the external environment are reported.