Goniometer, texture

Complex Anisotropy is studied in texture goniometers (p. 193) as a function of sample orientation. If the study is aiming at quantitative analysis of scattering data, the absorption correction may become an issue. Conversely, by choosing a special kind of scanning modus (e.g., symmetrical reflection SAXS SRSAXS), the absorption correction problem can be simplified. 

In general, it is not recommended to study WAXS crystallinity of anisotropic materials. The recording of the corresponding data is laborious, because the WAXS must be recorded as a function of both scattering angle and sample orientation in a texture goniometer (cf. p. 193, Fig. 9.3) before the data can be isotropized. 

Whenever we are considering orientation, we are dealing with anisotropic scattering data. Orientation is most frequently analyzed in 2D scattering data with fiber symmetry or in pole-figure data recorded by means of a texture goniometer. 

Figure 9.3. Scattering geometry for the measurement of pole figures in a texture goniometer. The scattering angle 20/,/./ is fixed, (p and (// are scanned...

In practice, either a pole figure has been measured in a texture-goniometer setup, or a 2D SAXS pattern with fiber symmetry has been recorded. In the first case we take the measured intensity g (pole figure. In the second case we can choose a reflection that is smeared on spherical arcs and project in radial direction over the range of the reflection. From the measured or extracted intensities I (orientation parameter by numerical integration and normalization... 

Figure 3 shows a Siemens texture goniometer. The technique of pole figure measurement in the reflection mode was proposed by Schulz as early as 1949... 

Fig. 3. A Siemens texture goniometer a x ray tube 6 collimator c-c 0 and 20 circles d specimen e Eulerian craddle /. slits g detector...

Texture studies on wires and plates are very important. Initial information can be acquired from transmission and reflection patterns recorded with a flat-film camera (see Fig. 1.5). The type and degree of texture can be determined more or less exactly, depending on the object of investigation and the type of instrument used. One of the best-developed instruments is the Liicke texture goniometer [125]. With this apparatus, the distribution of given net planes can be directly imaged in a pole figure. 

The fully automated, computer-controlled X-ray texture goniometer sold by Seifert allows reflection and transmission measurements the background is measured and the appropriate correction applied automatically. Other corrections, e.g., absorption, are also performed automatically. The pole figure is output to a terminal. Several reflections can be measured in a fully automated programmed sequence. 

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