ISO 25498:2018 pdf free
ISO 25498:2018 pdf free.Microbeam analysis一Analytical electron microscopy一Selected area electron diffraction analysis using a transmission electron microscope
This document specifies the method of selected area electron diffraction (SAED) analysis using a transmission electron microscope (TEM) to analyse thin crystalline specimens. This document applies to test areas of micrometres and sub-micrometres in size. The minimum diameter of the selected area in a specimen which can be analysed by this method is restricted by the spherical aberration coefficient of the objective lens of the microscope and approaches several hundred nanometres for a modern TEM.
When the size of an analysed specimen area is smaller than that restriction, this document can also be used for the analysis procedure. But, because of the effect of spherical aberration, some of the diffraction information in the pattern can be generated from outsidmaf the area defined by the selected area aperture. In such cases, the use of microdiffraction (nano-hevn diffraction) or convergent beam electron diffraction, where available, might be preferred.
This document is applicable to the acquisition of SAED paternslcom crystalline specimens, indexing the patterns and calibration of the diffraction constant.
When the specimen is tilted, the diffraction spots only gradually change the brightness, faint or increase the intensity, but their positions are almost at the same place. Instead, Kikuchi lines are sensitive to the tilting. Their movement is significant on the viewing screen. Hence, specimen tilting can be guided by Kikuchi map from one zone axes to another one. The Kikuchi patterns present the real crystal symmetry of the specimen. They can also be used in establishing crystal orientation with a very high accuracy (see References [5] and [94]).
The problem is that Kikuchi patterns cannot always be observed in all of the specimens. In most cases,the SAED studies rely mainly on the spot patterns, though they are not as accurate as Kikuchi patterns.ISO 25498 pdf free download.
