Thermostimulated surface autosegregation in bismuth ferrite single crystals |
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| Authors: | Yu. Ya. Tomashpolsky and N. V. Sadovskaya |
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| Affiliation: | (1) Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, Bd. Elisabeta no. 12, Bucharest, Roumania;(2) ICPE-CA, Splaiul Unirii no. 313, Bucharest, Roumania;(3) Department of Oxide Materials Science and Engineering, Faculty of Applied Chemistry and Materials Science, Polytechnic University of Bucharest, Gh. Polizu Street no. 1-7, 011061 Bucharest, Roumania;(4) Institute of Physical Chemistry, Splaiul Independentei no. 202, 060021 Bucharest, Roumania; |
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| Abstract: | The chemical and phase composition and morphological features of the surface nanostructure have been studied by the methods of high-resolution scanning electron microscopy, X-ray microprobe analysis, and atomic force microscopy in bismuth ferrite single crystals. This structure was formed as a result of the thermostimulated surface segregation after annealing in air or vacuum at the pressure of 10−4 Pa. It has been experimentally found that, at temperatures less than 500°C, Bi2F4O9 nanoparticles were formed due to the selective diffusion of iron atoms to the surface. Starting from 300°C in vacuum and 450°C in air, the segregating atom type changed and nanophases with high bismuth concentration (sillenites Bi26 − x Fe x O39 and Bi2O3 appeared in some regions. The partial orientation of new phases has been observed in some surface regions. A probable mechanism of the described phenomenon that represents a combination of selective intrinsic mass-transport of atoms from the bulk to the surface and their thermal evaporation has been discussed. |
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