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Structure refinement and X-ray powder diffraction data for kalipyrochlore (K,Sr,Na,Ca,H2O)2−m(Nb,Ti)2−xO6−wY1−n, with (0<m<0.8, x∼0.2, W = 0 and 0.2<n<1)

Published online by Cambridge University Press:  10 January 2013

S. Philippo ,
J. Naud ,
J. P. Declercq  and
J. Feneau-Dupont
S. Philippo
Affiliation:
Université Catholique de Louvain, Laboratoire de Géologie et Minéralogie, Pl. L. Pasteur, 3, 1348 Louvain-la-Neuve, Belgium
J. Naud
Affiliation:
Université Catholique de Louvain, Laboratoire de Géologie et Minéralogie, Pl. L. Pasteur, 3, 1348 Louvain-la-Neuve, Belgium
J. P. Declercq
Affiliation:
Université Catholique de Louvain, Laboratoire de Chimie Physique et de Cristallographie, Pl. L. Pasteur, 1, 1348 Louvain-la-Neuve, Belgium
J. Feneau-Dupont
Affiliation:
Université Catholique de Louvain, Laboratoire de Chimie Physique et de Cristallographie, Pl. L. Pasteur, 1, 1348 Louvain-la-Neuve, Belgium
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Abstract

The kalipyrochlore (K,Sr,Na,Ca,H2O)2−m(Nb,Ti)2−xO6−wY1−n, with (0<m<0.8, x∼0.2, w = 0 and 0.2<n<1) from Lueshe, Zaire is a defect pyrochlore species whose A-site weakly depleted. The measured powder diffraction is presented with a calculated figure of merit F(30) = 74.7(0.010,39). The structure has been refined by single-crystal from X-ray diffraction data collected on a Huber four-circle diffractometer and by Rietveld analysis from X-ray powder diffraction data. The slightly weathered crystal (studied by single crystal) has a cubic pyrochlore-type structure with the same atomic positions and a unit-cell parameter a = 10.603(5) Å, space group (S.G.): Fd3m. The highly weathered crystal (studied by Rietveld) has the same cubic pyrochlore-type structure except for the oxygen position. The oxygen moved from the 48f position with x, y, z equal to 0.284, 0, 0 to x = 0.308(5), y = 0.024(6) and z = –0.028(9). The cell parameter is a = 10.569(6)±0.0007 Å. These modifications of positions induce a distortion of the A-site into an hexagonal bipyramid and an elongation of the B-site along the c axis of the octahedron.

Keywords

kalipyrochloreX-ray diffractionstructure refinementpowder pattern
Type
Research Article
Information
Powder Diffraction , Volume 10 , Issue 3 , September 1995 , pp. 180 - 184
Copyright
Copyright © Cambridge University Press 1995

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