Structural Investigation of the Substituted Pyrochlore AgSbO3 through Total Scattering Techniques

• Published in: Inorganic chemistry Vol. 52; no. 19; pp. 11530 - 11537
• Main Authors: Laurita, Geneva, Page, Katharine, Sleight, A. W, Subramanian, M. A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 07-10-2013
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic401860j

Polycrystalline samples of the pyrochlore series Ag1–x M n x SbO3+x[(n–1)/2] (M = Na, K, and Tl) have been structurally analyzed through total scattering techniques. The upper limits of x obtained were 0.05 for Na, 0.16 for K, and 0.17 for Tl. The Ag+ cation occupies a site with inversion symmetry on a 3-fold axis. When the smaller Na+ cation substitutes for Ag+, it is displaced by about 0.6 Å perpendicular to the 3-fold axis to achieve some shorter Na–O bond distances. When the larger Tl+ cation substitutes for Ag+, it is displaced by about 1.14 Å along the 3-fold axis and achieves an environment typical of a lone pair cation. Some of the Tl3+ from the precursor remains unreduced, leading to a formula of Ag0.772(1)Tl+ 0.13(2)Tl3+ 0.036(1)SbO3.036(1). The position of the K+ dopant was effectively modeled assuming that K+ occupied the same site as Ag+. The expansion of the lattice caused by substitution of the larger K+ and Tl+ cations results in longer Ag–O bond lengths, which would reduce the overlap of the Ag 4d and O 2p orbitals that compose the valence band maximum. Substitution of the smaller Na+ results in a decrease in the Ag–O bond distance, thus increasing the overlap of the Ag 4d and O 2p orbitals. This will have a direct influence on the band composition and observed properties of this material of interest.