Synthesis, structural and physico-chemical characterization of new defect pyrochlore-type antimonates K0.42Lny′Sb2O6+z′ and Na0.36LnySb2O6+z (0 y, y′,z, z′ l; Ln = Y, Eu and Gd) prepared by soft chemistry route

Most of the pyrochlore-type compounds known and reported in the literature were prepared by solid state reactions, at elevated temperature (similar to1100degreesC). Alternatively, a new series of compounds, with formula K(0.42)Ln(y')Sb(2)O(6+z') and Na(0.36)Ln(y)Sb(2)O(6+z) (0 < y,y' (with 0 < y, y', z, z' < 1 and Ln = Y, Eu and Gd) was isolated, using a soft chemistry route from solutions. The good crystallinity of the samples allowed their structural determination using Rietveld refinement from X-ray powder diffraction data. They show a defect pyrochlore-type structure, with Fd3m space group and unit cell parameters close to 10.28 Angstrom. The occupied sites are: (Na, Ln) in site 16d, Sb in site 16c, O in site 48f, K and O' in site 8b. (C) 2003 Elsevier B.V. All rights reserved.