HIGH TEMPERATURE LAUE METHOD WITH POLYCHROMATIC SR: ITS APPLICATION TO QUARTZ PHASE TRANSITION

Kazumasa Ohsumi,^a Yoshikazu Miyata,^b Katsuhiro Kusaka,^a Takeshi Nakagawa,^a and

Kenji Hagiya^c

^aPhoton Factory, Inst. Materials Structure Science, KEK, Tsukuba, 305-0801, Japan; ^bGraduate School for Advanced Studies, KEK, Tsukuba, 305-0801, Japan; ^cFaculty of Science, Himeji Institute of Technology, Hyougo, 678-1297, Japan (kazumasa.ohsumi@kek.jp)

The Laue method is advantageous for obtaining diffraction data from a crystal at both low and high temperatures, because perturbative air-flow around the sample is reduced due to the stationary crystal when using polychromatic SR.

Low and high temperature equipment and a control system for observation through an optical microscope(LK-600PH; Linkam Scientific Instruments Ltd.) was developed and installed vertically on the Laue camera at BL-4B1 of the Photon Factory, KEK, Tsukuba. The Laue camera was originally developed for diffraction studies especially for sub-micrometer sized specimens and/or micrometer sized area of a larger sample[1],[2]. Taking into account the possibility of a thermal gradient within the sample, the Laue camera is suitable for our purpose. The low and high temperature system on the Laue camera was applied to the a–b phase transition of quartz(SiO₂), because it is well known that a modulated structure exists in the narrow temperature range between a–b quartz[3].

Diffraction data were obtained from a- to b-phase through the modulated structure region at 0.1 K steps. Satellite-reflection profiles and intensities around the main spots clearly changed at each temperature, partially shown in the figure below. Refinements of a- to b-quartz were carried out including substructure of the modulated structure region. The result indicates that the changes of positional and anisotropic thermal parameters describe the behavior of the oxygen atom through modulated structure region.

T_im : Temperature at maximum intensities of satellite reflections

References

1 Ohsumi, K., Hagiya, K. and Ohmasa, M. (1991) Jour.Appl.Cryst. 24, 340-348.

2 Ohsumi, K., Hagiya, K., Uchida, M., Suda, N., Miyamoto, M., Kitamura, M. and Ohmasa, M. (1995) Rev. Sci. Instrum. 66(2), 1448-1450.

3 van Tendeloo, G., van Landuyt, J. and Amelinckx, S.(1976) Phys. Stat. Sol. (a) 33, 723-735.