Enhancing of Small Isolated Domains and Superstructures in High Resolution Images of Oxides
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ENHANCING OF SMALL ISOLATED DOMAINS AND SUPERSTRUCTURES IN HIGH RESOLUTION IMAGES OF OXIDES J.G. PEREZ-RAMIREZ , D. MICHEL AND R. PORTIER+ *Instituto de Fisica, UNAM, a.p. 20-364, 01000 M~xico D.F., +CECM-CNRS, 15 Rue Georges Urbain, 94400 Vitry-Sur-Seine, France.
Mexico.
ABSTRACT the Starting from electron microscope high resolution images we apply technique of digital image processing to analyze some structural properties of oxides. We identify the structural features in the images that give origin to the diffuse scattering observed in the electron diffraction patterns of these oxides. We obtain results for three different systems: YBaCuO and BiSrCaCuO high temperature superconductors and mullite (type germanate). The analysis and enhancement of the images is done by filtering them in their Fourier space.
INTRODUCTION With the discovery of the high temperature superconductors [1] the specially in the case of ceramic science has received a new development, oxides. The physical characterization is now so important a the chemical one. All the experimental techniques developed during the last 30 years are now intensively used to research the properties in these materials [2,3,4]. Recently, the technique of digital image processing has been applied with good results in the solid state physics. Principally for enhancement and analysis of electron microscope images [5,6,7]. For the specific case of high temperature superconductors, it is known that electron diffraction patterns of the YBa Cu O7 samples show a diffuse scattering by values of x between 0 and 0.5 f8]. fn this work, we show the structural origin of this diffuse scattering by analysis of high resolution images. For the Bi 2 Sr 2 Ca Cu 0 high temperature superconductor the use of digital image processing iey us identify superstructures in the real space, which are observed by electron diffraction [9]. Finally, we show the importance of digital image processing techniques to identify the grow of superstructures and domains of different structures in mullite. The analysis emphasize the diffuse scattering observed in the Fourier space of high resolution electron images [9].
EXPERIMENTAL PROCEDURE Details about sample preparation in the systems analyzed in this work are reported elsewhere [8,9]. TEM observations were carried out in a JEM-4000 EX and a JEOL-200 C electron microscope with a high resolution pole piece. The images were digitized with a commercial and with a high sensibility LHESA video camera. To display images we have used an INOVION system. The software employed to process images is that developed by one of us [10], written in FORTRAN. This software was also simulated employing SEMPER V. For the image processing we have used a VAX-750 computer and a PC microcomputer.
RESULTS Fig. la shows an electron microscope high resolution image of a The zone axis is along the c axis. The YBa 2 Cu 3 O 6. superconducting sample. image shows the existence of superstructures along the a-axis with a distance of two times the lattice parameter a. The figure sho
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