NATURE OF THE SURFACE-LAYER IN ABO(3)-TYPE PEROVSKITES AT ELEVATED-TEMPERATURES

X-ray diffraction measurements showed that in the surface layer of per ovskite structure BaTiO3, SrTiO3, PbTiO3 and KNbO3 crystals at elevate d temperatures (500-1000 degrees C) reactions take place in the solid phase, associated with segregation in the direction to the surface of AO complexes, leading to the formation of a whole homologue series of crystalline compounds with the general formula AO .(ABO(3))(n), n=1,2, ...,10,infinity. Lowered oxygen partial pressure may inhibit the segre gation processes and in the range of temperatures for which vaporisati on of the AO complexes from the surface does not yet take place a suit able choice of oxygen pressure may lead to resynthesis of the compound .