THE DETERMINATION OF CRYSTAL STRUCTURE AND TEXTURE PARAMETERS OF POLYCRYSTALLINE THIN FILMS USING MULTIPLE DIFFRACTION DATASETS. H. Toraya, Ceramics Research Laboratory, Nagoya Institute of Technology Asahigaoka, Tajimi 507, Japan

Polycrystalline thin film/powder samples often exhibit the texture (preferred orientation) effect. The intensity correction for texture effect is, however, apt to induce the correlation with other parameters, and makes a result of crystal structure analysis less reliable. In the present study, a new procedure using multiple differaction datasest for the determination of crystal structure and texture parameters of polycrystalline thin films is proposed.

A sample used for the present study was a polycrystalline Bi₃Fe₅O₁₂ thin film. A wide-angle two-axis thin-film diffractometer based on a parallel-beam optics was used for data collection. Multiple diffraction datasets were obtained by using an asymmetric 2 [[theta]] scan technique at various fixed incident angles ranging from 1deg. to 30deg.. An individual profile fitting technique was used for pattern decomposition. In asymmetric diffraction, the scattering vector does not coincide with the polar axis of the specimen. Thus each of these datasets exhibited the different degree of texture effect. In previous studies, a Rietveld refinement technique was applied separately to individual diffraction datasets [1,2].

In the present study, all integrated intensity datasets observed at different incident angles were simultaneously used for the least-squares determination of crystal structure and texture parameters of the specimen.

The function of symmetrized harmonics expansion [3] was used to correct the intensity for preferred orientation. The accuracy of refined parameters was improved compared to the result obtained by using single scan datasets. The present technique will be applied to powder specimens with preferred orientation effect.

[1] Toraya, H. and Okuda, T., J. Phys. Chem. Solids, 56, 1317-1322 (1995).

[2] Toraya, H. Proceedings for Europian Powder Diffraction Conference

(EPDIC) IV (1995) (submitted).

[3] Jarvinen, M., J. Appl. Cryst., 26, 525-531 (1993).