Mikrochim. Acta 125, 13-19 (1997) Mikrochimica Acta 9 Springer-Verlag 1997 Printed in Austria Quantitative Chemical Phase Imaging by Means of Energy Filtering Transmission Electron Microscopy* Werner Grogger, Ferdinand Hofer**, and Gerald KothMtner Forschungsinstitut ffir Elektronenmikroskopie, Technische Universit~it Graz, Steyrergasse 17, A-8010Graz, Austria Abstract. Electron spectroscopicimaging (ESI)in the transmission electron microscope (TEM) is a powerful method to produce 2- dimensional elemental distribution maps. These maps show in a clear way the chemicalsituation of a small specimenregion.In this work we used a Gatan Imaging Filter (GIF) attached to a 200 kV TEM to investigate a Ba-Nd-titanate ceramic. The three phases occuringin this material could be visualized using inner-shell ioniz- ation edges(Ba M45,Nd M45and Ti L23).We applied differentimage correlation techniques to the ESI elemental maps for direct visualiz- ation of the chemical phases. First we simply overlaid the elemental maps assigning each element one colour to form an RGB image. Secondly we used the technique of scatter diagrams to classify the different phases. Finally we quantified the elemental maps by divid- ing them and multiplyingthem by the appropriate inner-shell ioniz- ation cross-sectionswhich gave atomic ratio images. By using these methods we could clearlyidentifyand quantifythe variousphases in the Ba-Nd-titanate specimen. Key words: analytical electron microscopy,electron spectroscopic imaging, atomic ratio images, Ba-Nd-titanate ceramic. Nowadays electron energy loss spectrometry (EELS) is a routine method in the transmission electron micro- cope (TEM) [1]. Because of its spatially-resolved nature EELS is the basis of energy filtered imaging (energy filtering transmission electron microscopy = EFTEM or electron spectroscopic imaging= ESI). The recent years have brought some developments which made this technique simpler to use and to be applied both in biology ([2], [3]) and in materials science (I-47, [5], [6]). Energy filtering devices for the TEM have become commercially available: The Zeiss EM 912 Omega TEM with an operational voltage of 120kV (1,7], 1,-8]) and the Gatan Imaging Filter (GIF) which can be attached to practically any 100-400kV TEM ([9], [10]). * Dedicated to ProfessorDr. rer. nat. Dr. h.c. Hubertus Nickel on the occasionof his 65th birthday ** To whom correspondenceshould be addressed With an energy filter some essential advantages for TEM work become accessible: First the contrast and resolution of TEM images and electron diffrac- tion patterns can be improved appreciably by choosing only elastically scattered electrons with the filter (zero loss filtering). The inelastically scattered elec- trons which are very troublesome for conventional TEM imaging are thus eliminated; chromatic abber- ations and delocalizations of the inelastic scattering processes are minimized. Secondly any spectral feature of the EEL-spectrum can be used for imaging (eg. plasmons, ionization edges). The inner-shell ionization edges in the EEL-spectrum are particularly useful be- cause they contain information about the chemical composition of the specimen. The ionization edges are caused by inner-shell excitation of the atoms and the characteristic onset energies can be used to identify the chemical elements. Therefore energy filtered images recorded at the energy of an ionization edge can be used to derive two dimensional elemental distribution maps. In conventional TEM investigations one usually acquires energy dispersive X-ray (EDX-) or EEL- spectra from a small selected area (point analysis). Thus, the chemical composition of a small specimen region can be obtained quantitatively. However, the advantage of imaging methods lies in the simultaneous acquisition of 2-dimensional chemi- cal composition. With ESI, energy filtered images are acquired which can then be combined to show the distribution of the chemical elements in the specimen with nanometre resolution [11]. Similar information can be obtained using scanning techniques in the TEM (scanning transmission electron microscope = STEM). Nowadays field emission guns are widely available for