X-ray diffraction and Raman spectroscopy on Gd-2(Ti2-yTey)O-7 prepared at high pressure and high temperature

Abstract

A series of Te-substituted pyrochlores of stoichiometry Gd-2(Ti2-yTey)O-7 (y <= 0.2) were prepared under high-pressure and high-temperature conditions and characterized by X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. X-ray diffraction and X-ray photoelectron spectroscopy studies revealed that the Te4+ and Te6+ ions occupy the Ti4+ sites

the percentage of the contribution of Te6+ increases as tellurium content. These substitutions induce an increase of the volume of the TiO6 octahedron due to the increase in the Ti-O(2) bond length, which preserves the oxygen positional parameter (x(48f)) and the Gd-O(1) bond length. Results of Raman spectroscopy showed a significant shift to higher frequencies of the E-g mode associated to the O(2) sublattice, as well an increase in the full-width-at-half-maximum intensity (FWHM) of the F-2g mode (O-Gd-O bending) as the level of Te substitution for Ti increases. These results are discussed and compared with those reported in the literature. (C) 2010 Elsevier B.V. All rights reserved.