Structural studies on new ternary oxides <script type="math/tex">Ba_{8}Ta_{4}Ti_{3}O_{24}</script> and <script type="math/tex">Ba_{10}Ta_{7.04}Ti_{1.2}O_{30}</script>

Shpanchenko, R.V.; Nistor, L.; Van Tendeloo, G.; van Landuyt, J.; Amelinckx, S.

doi:10.1006/JSSC.1995.1086

Title

Structural studies on new ternary oxides $Ba_{8}Ta_{4}Ti_{3}O_{24}$ and $Ba_{10}Ta_{7.04}Ti_{1.2}O_{30}$

Author

Shpanchenko, R.V.

Nistor, L.

Van Tendeloo, G.

van Landuyt, J.

Amelinckx, S.

Abstract

The ternary oxides Ba8Ta4Ti3O24 and Ba10Ta7.04Ti1.2O30 were synthesized and their crystal structures and defects were studied by means of X-ray powder diffraction, electron diffraction, and high resolution electron microscopy. The crystal structure of Ba8Ta4Ti3O24 is based on the 8H (cchc)(2) close-packed stacking (a 10.0314 Angstrom, c = 18.869 Angstrom, SG P6(3)/mcm, Z = 3) and that of Ba10Ta7.04Ti1.2O30 and on the 10H (cchcc)(2) close-packed stacking (a = 5.7981 Angstrom, c = 23.755 Angstrom, SG P6(3)/mmc, Z = 1) of BaO3 layers. The structural refinements gave the following values for the R factors for Ba8Ta4Ti3O24 (Ba10Ta7.04Ti1.2O30) R(I) = 0.041 (0.039), R(P) = 0.108 (0.118), and R(wP) = 0.094 (0.099). The main feature of both structures is the presence of two types of face-sharing octahedra (FSO) with different occupancies by Ta atoms, Ti atoms, and vacancies, which results in the formation of a superstructure. It was shown that in the Ba8Ta4Ti3O24 structure these pairs of FSO occur in an ordered fashion and in the Ba10Ta7.04Ti1.2O30 structure in a disordered fashion. The existence of the wide range of solid solutions was shown to be also a consequence of the presence of one of the two types of face-sharing octahedra. (C) 1995 Academic Press, Inc,

Language

English

Source (journal)

Journal of solid state chemistry. - London

Publication

London : 1995

ISSN

0022-4596

DOI

10.1006/JSSC.1995.1086

Volume/pages

114 :2 (1995) , p. 560-574