EDS Data Research Articles

The crystal structure of eugaAl

A polycrystalline specimen of nominal formula EuGaAl with unknown crystal structure was investigated by various electron microscope techniques; EDS-, SED-, and CBED data were taken on a Philips 400 electron microscope operated at 100kV, HREM data on a Hitachi 9000 microscope operated at 300kV. The EDS data confirmed the composition for the bulk of the material but, in addition, revealed particles with other fractions of the elements. Only the EuGaAl particles were further investigated. The unit cell was determined to be orthorhombic with a ratio: a/b=0.969(2) , a/c=0.234(2) and b/c=0.234(2). The lattice constants are a=4.54(5)Ȧ, b=4.68Ȧ and c=19.97(20)Ȧ. Based on systematic extinctions for hkl reflections with h+l=2n+l, the unit cell was found to be b-centered. CBED patterns of the [001], [100], and [010] zone axes are shown in Fig. 1. The zone axis patterns are in agreement with the above stated data except for diffused (2m+l,2n+l,0)- reflections, not compatible with the above stated systematic absences. But these occurred only occasionally in conjunction with a complicated noncommensurate superlattice pattern.

Analytical electron microscopy of Nafion ion exchange membranes

Ion exchange membranes, widely used in many electrochemical techniques, have become of major interest in water purification as part of new environmental technologies and in the highest purification of water for industrial purposes. Nafion 117, a product of the Du Pont Company showing high ionic conductivity and good mechanical properties, is a promising candidate for future applications. The principles of analytical electron microscopy were used to study the ion exchange membrane. Imaging showed ionic percolation in the polymer. No staining method was applied, to ensure artefact-free images of the membrane. Electron diffraction gives additional information about the cross-linked structure while EDS and EELS data provide information on chemical composition and ion exchange efficiency. Results were obtained using two independent methods of specimen preparation.

Electron diffraction studies of amorphous and polycrystalline thin films

The study of amorphous and polycrystalline materials by obtaining radial density functions G(r) from X-ray or neutron diffraction patterns is a well-developed technique. We have developed a method for carrying out the same technique using electron diffraction in a standard TEM. It has the advantage that studies can be made of thin films, and on regions of specimen too small for X-ray and neutron studies. As well, it can be used to obtain nearest neighbour distances and coordination numbers from the same region of specimen from which HREM, EDS and EELS data is obtained.The reduction of the scattered intensity I(s) (s = 2sinθ/λ ) to the radial density function, G(r), assumes single and elastic scattering. For good resolution in r, data must be collected to high s. Previous work in this field includes pioneering experiments by Grigson and by Graczyk and Moss. In our work, the electron diffraction pattern from an amorphous or polycrystalline thin film is scanned across the entrance aperture to a PEELS fitted to a conventional TEM, using a ramp applied to the post specimen scan coils. The elastically scattered intensity I(s) is obtained by selecting the elastically scattered electrons with the PEELS, and collecting directly into the MCA. Figure 1 shows examples of I(s) collected from two thin ZrN films, one polycrystalline and one amorphous, prepared by evaporation while under nitrogen ion bombardment.

On phase formation and superconducting transition in the BiSrCaCuO system

The influence of excess Cu in the precursor on phase formation and the superconducting transition temperature in the Bi-Sr-Ca-Cu-O system has been studied. XRD, SEM and EDS data for the investigated materials were correlated to the results of resistivity and ac-susceptibility measurements.

Rad: A Comprehensive Software System for Analytical Electron Microscopy

An analytical electron microscope (AEM) provides the capability of obtaining both compositional and crystallographic information. While the acquisition and reduction of x-ray EDS data is generally done by a small computer, the acquisition and analysis of electron diffraction data has remained a manual, off-line technique. A recently described technique1 has made possible the real-time acquisition and reduction of electron diffraction data with an AEM. However, as is the case with EDS analysis, electron diffraction analysis requires that a rather large body of data be processed in order to produce a relatively simple result.