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Un goniomètre original très précis pour la diffraction des rayons X sur poudre à température controlée
Author(s) -
Bérar J. F.,
Calvarin G.,
Weigel D.
Publication year - 1980
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889880011934
Subject(s) - goniometer , diffraction , monoclinic crystal system , optics , reproducibility , materials science , triclinic crystal system , physics , analytical chemistry (journal) , crystallography , chemistry , crystal structure , chromatography
A new goniometer for X‐ray powder diffractometry and its setting are described. The diffraction angles are easily and quickly measured with high accuracy (10 −3 °θ), even if experiments require the use of some large or heavy device such as a cryostat or furnace. An original mechanical design allows a direct measurement of the angular position, 20, of the receiving slit, by means of an incremental (10 −3 °) photoelectric encoder. Three independent stepping motors, for the θ and 2θ scans and the sample translation, allow one to define with a very good reproducibility the `zero' goniometer position. Diagrams of Pb 3 O 4 and Pb(NO 3 ) 2 have been recorded in continuous scanning (0.05°θ/min): differences between θ of the two diffraction lines recorded on each side of the goniometer do not exceed ±2 × 10 −3 °, and reproducibility of measurements is better than +1 × 10 −3 °. Sensitivity of angular measurements is very good; it is proved by studying, in the range 9–40° (θ), the thermal expansion of Pb(NO 3 ) 2 between 273 and 291 K. Moreover, use of a large radius (500 mm) and of a set of undivergent slits improves angular resolution, principally for θ<20°, which is very important for molecular‐compound studies: an example is given showing diffraction line splitting due to a monoclinic triclinic phase transition.