Electronic Probes X-ray Microanalysis (EPMA)
Electronic Probes X-ray Microanalysis (EPMA)

Electron Microprobe, full name of the electronic probe X-ray microanalysis, also known as micro-area X-ray spectrum analyzer. The sample can be a small area composition analysis. In addition to H, He, Li, Be and other lighter elements, there are elements beyond U can be qualitative and quantitative analysis.

Large quantities of electron microprobes use an extremely narrow electron beam that has been accelerated and focused as a probe to excite a small area of ​​the sample that emits characteristic X-rays and determine the wavelength and intensity of the X-ray. The elements of the micro-area for qualitative or quantitative analysis.

The combination of scanning electron microscopy (SEM) and electron microprobe (SEM), microscopic observation of the microstructure and elemental composition, to solve the problem of material inhomogeneity has become a powerful tool for studying submicroscopic structures.

Analysis of working principle

There are three basic ways that an electron probe can work: Point Analysis For full-scale qualitative or quantitative analysis of selected points and for quantitative analysis of the elements contained in them. Line analysis is used to show changes in the concentration of elements along a selected straight line ; Surface analysis is used to observe the concentration distribution of elements in selected micro-regions.

According to Moseley's law, the characteristic X-rays of various elements have their own determined wavelengths. By detecting these X-rays of different wavelengths to determine the elements contained in the sample, this is the basis for the qualitative analysis of the electron probe. By comparing the diffraction intensity of the element Y in the sample to that of the standard sample, the quantitative analysis of the electron probe can be performed. Of course, the use of electron beam-induced X-ray elemental analysis, the premise is that the energy of the incident electron beam must be greater than the atomic electron core of a certain element of the ionization of the critical ionization energy.

Electronic probe advantages

1, can carry out micro-area analysis. Analyze the composition of several μm ^ 3 elements.
2, can conduct on-site analysis. No need to remove the sample from the sample, you can directly analyze the small area in a large sample. By combining the electron microscope with the electron probe, the microstructure and elemental composition observed under a microscope can be linked.
3, a wide range of analysis. Z> 4. Among them, the spectrum: Be ~ U, spectrum: Na ~ U.

Features and features

Electron probes can be qualitative or quantitative analysis of the chemical composition of small areas (microns) in the sample. Point, line scan (layer composition distribution information), surface scan analysis (component surface distribution image). Can also be fully automated batch (preset 9999 test point) quantitative analysis. Electron probe technology has the advantages of quick and easy operation (relatively complex chemical analysis methods), straightforward interpretation of experimental results, no damage to the sample during the analysis process, and high measurement accuracy. Therefore, in the field of metallurgy, geology, electronic materials, biology, Increasingly widespread use in medicine, archeology, and other fields is an important tool in mineral test analysis and sample composition analysis.

The main purpose

The principle is the use of focused high-energy electron beam bombardment of the solid surface, the bombarded elements to stimulate the characteristics of X-ray, according to its wavelength and intensity of the solid surface micro-area qualitative and quantitative chemical analysis. Mainly used to analyze the surface of fine particles of solid material or small area, the smallest diameter of about 1μm. Analysis of elements from the atomic number 3 (lithium) to 92 (uranium). Absolute sense of up to 10-14 to 10-15g. In recent years, the formation of a scanning electron microscopy - a combination of micro-analyzer device, the micro-morphology can be observed at the same time point by point analysis of the chemical composition and structure of the sample. Widely used in geological, metallurgical materials, cement clinker research and other departments.

Structural features

Using a fine-focus electron beam of about 1 Pm, the characteristic X-ray of the element is excited in the micro-region of the sample surface, and the chemical composition of the micro-zone is qualitatively or quantitatively analyzed according to the wavelength and the intensity of the characteristic X-ray. Electron probe optical system, vacuum system and other parts and scanning electron microscope is basically the same, usually with secondary electron and backscatter electronic signal detector, both the morphology and composition of the microstructure of both functions. In addition to the structure of the electronic probe and the scanning electron microscope structure similar to the host system, but also include spectroscopy systems, detection systems and other parts.

Electronic probe mainly by the electronic optical system (tube), X-ray spectrometer and information recording display system. Electron probes and scanning electron microscopes have basically the same configuration in electro-optical systems, and they are often combined into a single instrument.

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