Energy-dispersive spectrometer

An alternative type of spectrometer is the energy dispersive spectrometer which dispenses with a crystal dispersion element. Instead, a type of detector is used which receives the undispersed X-ray fluorescence and outputs a series of pulses of different voltages that correspond to the different wavelengths (energies) that it has received. These energies are then separated with a multichannel analyser. 

An energy dispersive spectrometer is cheaper and faster for multielement analytical purposes but has poorer detection limits and resolution. 

Energy dispersive spectrometers can, in general, collect the spectmm faster and are less expensive than the more sophisticated wavelength dispersive spectrometers. However, they do not have the resolution and cannot separate closely spaced lines as easily as the wavelength dispersive spectrometers. 

Both the wavelength dispersive and energy dispersive spectrometers are well suited for quaUtative analysis of materials. Each element gives on the average only six emission lines. Because the characteristic x-ray spectra are so simple, the process of allocating atomic numbers to the emission lines is relatively simple and the chance of making a gross error is small. 

The heart of the energy-dispersive spectrometer is a diode made from a silicon crystal with lithium atoms diffiised, or drifted, from one end into the matrix. The lithium atoms are used to compensate the relatively low concentration of grown-in impurity atoms by neutralizing them. In the diffusion process, the central core of the silicon will become intrinsic, but the end away from the lithium will remain p-type and the lithium end will be n-type. The result is a p-i-n diode. (Both lithium-... 

TEM observation and elemental analysis of the catalysts were performed by means of a transmission electron microscope (JEOL, JEM-201 OF) with energy dispersion spectrometer (EDS). The surface property of catalysts was analyzed by an X-ray photoelectron spectrometer (JEOL, JPS-90SX) using an A1 Ka radiation (1486.6 eV, 120 W). Carbon Is peak at binding energy of 284.6 eV due to adventitious carbon was used as an internal reference. Temperature programmed oxidation (TPO) with 5 vol.% 02/He was also performed on the catalyst after reaction, and the consumption of O2 was detected by thermal conductivity detector. The temperature was ramped at 10 K min to 1273 K. 

Permeation measurements were conducted on the Pd and Pd-Ag/PSS membranes at elevated temperature (623 K to 873 K) and pressures (up to 1 MPa). Surfece morphology of the deposited layer was observed with a scanning electron microscope (SEM, S3(K)0N, HITACHI Co.) equipped with an energy dispersive spectrometer (EDS, HORIBA Co.). 

R. Jenkins, Comparison of wavelength and energy dispersive spectrometers. In X-Ray Fluorescence Spectrometry, 2nd ed., Wiley-Interscience, New York, 1999, pp. 111-121 Chapter 7. 

Local composition is very useful supplementary information that can be obtained in many of the transmission electron microscopes (TEM). The two main methods to measure local composition are electron energy loss spectrometry (EELS), which is a topic of a separate paper in this volume (Mayer 2004) and x-ray emission spectrometry, which is named EDS or EDX after the energy dispersive spectrometer, because this type of x-ray detection became ubiquitous in the TEM. Present paper introduces this latter method, which measures the X-rays produced by the fast electrons of the TEM, bombarding the sample, to determine the local composition. As an independent topic, information content and usage of the popular X-ray powder dififaction database is also introduced here. Combination of information from these two sources results in an efficient phase identification. Identification of known phases is contrasted to solving unknown stmctures, the latter being the topic of the largest fiaction of this school. 

K. F.J. (1968) Solid-state energy-dispersion spectrometer for electron-microprobe X-ray analysis. 

X-ray microanalysis techniques— in particular, electron probe x-ray microanalysis (EPXMA or EPMA) and SEM coupled with energy dispersive spectrometers (EDS, EDX) are, by far, one of the surface analysis techniques most extensively used in the field of art and art conservation, and they have actually become routine methods of analyzing art and archaeological objects and monitoring conservation treatments [34, 61, 63]. 

SEM is particularly useful when integrated with an energy dispersive spectrometer (EDS), thereby allowing the determination of elemental composition of the materials that are also being observed and micrographed. Elemental composition of fibers and deposits has been studied in textiles from Etowah (51). The elemental composition reflects their burial environment in association with copper as well as their constituent plant fibers. Rowe (52) applied this technique successfully to pigments used in rock art, and it has been used in the study of archaeological fibers (11, 53-55). 

X-rays-energy dispersive spectrometer with printer. 

Energy dispersive spectrometer (EDS), in which a multichannel analyser gives the photon energy spectrum. 

Figure 4. Inhomogeneity of silica-aluminas prepared by various methods. A series of 17 commercial samples of silica-aluminas from seven different producers was submitted to microanalysis. All of them showed considerable fluctuations of composition at the scale of several tens of nanometers to several micrometers. These samples were prepared by coprecipitation or by the sol-gel method. It is not known whether some of these samples were prepared from alkoxides. Smaller but significant fluctuations at the micrometer scale were also observed for two laboratory samples prepared from alkoxides. The samples were dispersed in water with an ultrasonic vibrator. A drop of the resulting suspension was deposited on a thin carbon film supported on a standard copper grid. After drying, the samples were observed and analyzed by transmission electron microscopy (TEM) on a JEOL-JEM 100C TEMSCAN equiped with a KEVEX energy dispersive spectrometer for electron probe microanalysis (EPM A). The accelerating potential used was 100 kV.

As the scanning electron microscope is dedicated to the study of textures or morphologies, it is generally used with an energy dispersive spectrometer (EDS) which is not particularly sensitive to the topography of the sample and compatible with the low probe currents. 

The energy dispersive. spectrometer (Fig. 7.12) comprises a semi-conductor detector (diode) that collects the entire X-ray spectrum and transmits it to a multi-channci analyser which classes the various X-ray spectrum lines as a function of their energy. 

Bowman L. E., Spilde M. N., and Papike J. J. (1997) Automated energy dispersive spectrometer modal analysis applied to diogenites. Meteorit. Planet. Sci. 32, 869-875. 

---