CRYSTALLOGRAPHIC STUDIES OF BROOKITE(TiO2) WITH SYNCHROTRON RADIATION. Masahiko TANAKA, Photon Factory, National Laboratory for High Energy Physics, 1-1 Oho, Tsukuba, Ibaraki 305 Japan.

X-ray diffraction studies on single crystals of brookite(TiO2) with synchrotron radiation have been performed. It is found that extra reflections are observed, which is forbidden by the extinction rule for the brookite space group. It is well known brookite crystal have two kinds of crystal habit, one is platy and the other is pyramidal. This is an interesting problem why two kinds of crystal habit are observed from the point of crystal morphology. Hartman¹ suggested that platy habit crystal made by epitaxial growth of SiO2 on the {001} brookite as the result of PBC analyses. I think it may be possible to observe structural distortion caused by such epitaxial growth by using strong X-ray source, so I carry out single crystal X-ray diffraction studies of brookite with synchrotron radiation. A crystal with pyramidal habit from Magnet cove, Arkansas, USA used for diffraction studies. The diffraction experiments were done with vertical type 4-circle diffractometer at BL-10A, Photon Factory, National Laboratory for High Energy Physics, using radiation of the 0.7 Å wavelength. Intensity data of 1557 reflections were collected from the following range; 2-[[theta]] < 65 degrees, -17 < h < 17, 0, 0 < k,l < 16. As the results, some forbidden reflections for brookite space group Pbca, such as h00,k00,00l;h,k,l=2n+1, 0hk;h=2n+1, h0l;l=2n+1 or hk0;h=2n+1, are observed. The intensity of these reflections is lower than that of the fundamental reflection by three orders of magnitude. There is no reflection that suggests existence of super lattice by measurements of diffraction profile along h00. Diffraction studies using a platy habit single crystal are in progress. The reason these extra reflections appear and the relationship between the crystal habit and these extra reflections will be discussed.

¹ Hartman,P.(1965), C.N.R.S.,601-618