Electronic Structures and Dielectric Properties of Substituted BaTiO_3

概要

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Electronic structures were investigated on BaTiO_3 substituted with other elements, such as Ca, Sr, Sc, Y, Ce and Gd for Ba, using a molecular orbital treatment that yielded net charge, bond order, density of states, energy levels and contour maps of electron density. By this method, the transformation into paraelectric material by ferroelectric material was discussed with respect to relative permittivity as measured experimentally. Furthermore, X-ray photoelectron spectroscopy (XPS) at the valence energy level was used on the Sr-substituted cluster, and the experimental spectrum was compared to the calculated one to evaluate the appropriateness of the cluster model. The overlap population between the A site in BaTiO_3 and oxygen showed either a covalent or ionic nature depending on the elements. In addition, the relative permittivity related to the overlap population between site A and Ti resulting in lower permittivity for the trivalent elements such as Y and Gd. The computer simulation can be applied to design properties of the ceramics in the microwave range.
社団法人応用物理学会の論文
1997-09-30