LAYER STRUCTURES BAO-BATIO3 IN THE REGION OF P-TYPE CONDUCTIVITY ON THE SURFACE OF BATIO3

X-ray diffraction measurements on the surface of polycrystalline BaTiO3 show that a reversible process of defect segregation occurs in the temperature range from 500 to 1000-degrees-C and in the air pressure range from 10(-2) to 760 torr. This causes the appearance and disappearance of new crystalline phases of the formula Ban+1TinO3n+1 (n = 1,2,3). These findings amend the present defect models developed on the basis of measurements of the p-type equilibrium conductivity as a function of oxygen partial pressure.