International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

© International Union of Crystallography 2006
International Tables for Crystallography (2006). Vol. C. ch. 2.3, pp. 53-54

Section 2.3.1.5. Microdiffractometry

W. Parrisha‡ and J. I. Langfordb

a IBM Almaden Research Center, San Jose, CA, USA, and bSchool of Physics & Astronomy, University of Birmingham, Birmingham B15 2TT, England

2.3.1.5. Microdiffractometry

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There are two types of microdiffraction: (a) only a very small amount of powder is available, and (b) information is required from very small areas of a conventional-size specimen. Small-volume samples have been analysed with a conventional diffractometer by concentrating the powder over a small spot centred on a single-crystal plate such as silicon (510) or an AT-cut quartz plate, or on Mylar for transmission. It is essential to rotate the specimen and increase the count time. A Gandolfi camera has also been used for very small specimens (see Section 2.3.4[link]). A high-brilliance microfocus X-ray source has been used with a collimator made of 10 to 100 μm internal-diameter capillary tube. An X–Y stage is used with an optical microscope to locate selected areas of the specimen.

A microdiffractometer has been designed for microanalysis, Fig. 2.3.1.15[link] (Rigaku Corporation, 1990[link]). It has been used to determine phases and stress in areas [\lt\, 10^4] μm2 (Goldsmith & Walker, 1984[link]). The key to the method is the use of an annular-ring receiving slit, which transmits the entire diffraction cone to the detector instead of a small chord as in conventional diffractometry, thereby utilizing all the available intensity. The pattern is scanned by translating the ring and detector along the direct-beam path so that [2\theta = \arctan (R _{\rm RS}/L), \eqno (2.3.1.26)]where [R_{\rm RS}] is the radius of the ring slit and L the distance from the fixed specimen. For RRS = 15 mm, L varies from 171 to 9 mm in the transmission range 5 to 60°2θ; a 50 mm diameter scintillation counter is used. A doughnut-shaped proportional counter (3/4 of a full circle) is used for the 30 to 150° reflection specimen mode. The slit width is 0.2 mm and the aperture varies with 2θ. The intensities fall off at the higher 2θ's because of the small incidence angles to the slit. An alternative method uses a position-sensitive proportional counter. Steinmeyer (1986[link]) has described applications of microdiffractometry.

[Figure 2.3.1.15]

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Rigaku microdiffractometer for microanalysis. C collimator, PC ring proportional counter, RS ring slit with radius r, S specimen, SC scintillation counter, PBS primary beam stop, PH pinhole for alignment, L specimen-to-receiving-slit distance.

By using synchrotron radiation (Section 2.3.2[link]), single-crystal data for structure determination can now be obtained from a microcrystal about 5–10 μm in size; see Andrews et al. (1988[link]), Bachmann, Kohler, Schultz & Weber (1985[link]), Harding (1988[link]), Newsam, King & Liang (1989[link]), Cheetham, Harding, Mingos & Powell (1993[link]), Harding & Kariuki (1994[link]), and Harding, Kariuki, Cernik & Cressey (1994[link]).

References

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 First citation Bachmann, R., Kohler, H., Schultz, H. & Weber, H.-P. (1985). Structure investigation of a 6 µm CaF2 crystal with synchrotron radiation. Acta Cryst. A41, 35–40.Google Scholar
 First citation Cheetham, G. M. T., Harding, M. M., Mingos, D. M. P. & Powell, H. R. (1993). Synthesis and microcrystal structure determination of [Au10(PPh3)7{S2C2(CN)2}2]. J. Chem. Soc. Chem. Commun. pp. 1000–1001.Google Scholar
 First citation Goldsmith, C. C. & Walker, G. A. (1984). Small area X-ray diffraction techniques; applications of the microdiffractometer to phase identification and strain determination. Adv. X-ray Anal. 27, 229–238.Google Scholar
 First citation Harding, M. M. (1988). The use of synchrotron radiation for Laue diffraction and for the study of very small crystals. Chemical crystallography with pulsed neutrons and synchrotron X-rays, edited by M. A. Carrondo & G. A. Jeffrey, pp. 537–561. NATO Advanced Study Institute Series C, Vol. 221. Dordrecht: Kluwer Academic Publishers.Google Scholar
 First citation Harding, M. M. & Kariuki, B. M. (1994). Microcrystal structure determination of AlPO4-CHA using synchrotron radiation. Acta Cryst. C50, 852–854.Google Scholar
 First citation Harding, M. M., Kariuki, B. M., Cernik, R. J. & Cressey, G. (1994). The structure of aurichalcite, (Cu,Zn)5(OH)6(CO3)2, determined from a microcrystal. Acta Cryst. B50, 673–676.Google Scholar
 First citation Newsam, J. M., King, H. E. Jr & Liang, K. S. (1989). X-ray diffraction using synchrotron radiation – a catalysis perspective. Adv. X-ray Anal. 32, 9–20.Google Scholar
 First citation Rigaku Corporation (1990). Brochure describing equipment.Google Scholar
 First citation Steinmeyer, P. A. (1986). Special applications of the Debye microdiffractometer. Adv. X-ray Anal. 29, 251–256.Google Scholar








































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