New Ferroelectric Ba_5Ti_2O_7CI_4

概要

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A new crystalline material grown by the flux method and identified chemically and through density and structure determination as Ba_5Ti_2O_7Cl_4 has been synthesized, and is shown to possess ferroelectric properties. The structure is found to be orthorhombic at room temperature using powder method of X-ray diffraction. The lattice constants at room temperature are a=8.526A, b=7.608A and c=11.696A with an uncertainty of ±0.0025A. The crystal has a space group Pmc2_1, and the atomic positions are shown to confirm with the observed X-ray reflection intensities. It is found that two lattices related to each other by the interchange of a and b axes describe the crystal structure, and the X-ray intensities can be explained by considering the ions present on both the lattices for a given(hkl)plane. The use of the atomic scattering factors available in literature give the correct X-ray intensities, if the microstructure present in the crystal in the form of pronounced twinnings on planes(100), (200), (010), (020), (001), (020), (110), (220)is taken into account. The calculations are done using trial and error method anticipating the atomic positions.
社団法人応用物理学会の論文
2000-05-15