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Preparation and crystal data of the New Pyrochlores Pb 2 [M 1.5 Te 0.5 ]O 6.5 (M = Ti, Zr, Sn, Hf)
Author(s) -
Alonso J. A.,
Cascales C.,
Rasines I.
Publication year - 1986
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.19865370623
Subject(s) - crystallography , center (category theory) , materials science , oxygen , titanium , oxygen atom , x ray crystallography , crystal structure , diffraction , coordination number , analytical chemistry (journal) , chemistry , ion , physics , molecule , metallurgy , organic chemistry , chromatography , optics
From mixtures of PbO, MO 2 (M = Ti, Zr, Hf), SnO, and TeO 2 , four new oxides Pb 2 [M 1.5 Te 0.5 ]O 6.5 have been obtained as yellow powders giving X‐ray diffraction patterns characteristic of cubic pyrochlores, S.G. Fd 3 m (No. 227), Z = 8, and a/Å values from 10.3529(1) (M = Ti) to 10.7406(1) (M = Zr). The best R factors, from 0.0465 (M = Ti) to 0.0242 (M = Hf), were obtained for Pb in 16(c) positions, M and Te (3:1) randomly distributed in 16(d), oxygen atoms in 48(f) and in a half of the 8(a) sites, and x values for the oxygen positional parameter (origin at center, 3 m) from 0.436 (M = Ti) to 0.421 (M = Zr). For the compounds of Ti and Zr the angles of the coordination polyhedra around the metals are reported. For seven‐coordinated Pb II the stereochemical influence of the nonbonded electron pair is shown. Apparent interatomic distances agree with those calculated.