Determining the structure of tetragonal Y2WO6 and the site occupation of Eu3+ dopant

The compound Y2WO6 is prepared by solid state reaction at 750 degrees C using sodium chloride as mineralizer. Its structure is solved by ab-initio methods from X-ray powder diffraction data. This low temperature phase of yttrium tungstate crystallizes in tetragonal space group P4/nmm (No. 129), Z=2, a=5.2596(2) angstrom, c=8.4158(4) angstrom. The tungsten atoms in the structure adopt an unusual [YO6] distorted cubes coordination, connecting [YO6] distorted cubes with oxygen vacancies at the O-2 layers while other yttrium ions Y-2 form [YO8] cube coordination. Y3+ ions occupy two crystallographic sites of 2c (C-4v symmetry) and 2a (D-2d symmetry) in the Y2WO6 host lattice. With Eu3+ ions doped, the high resolution emission spectrum of Y2WO6:Eu3+ suggests that Eu3+ partly substituted for Y3+ in these two sites. The result of the Rietveld structure refinement shows that the Eu3+ dopants preferentially enter the 2a site. The uniform cube coordination environment of Eu3+ ions with the identical eight Eu-O bond lengths is proposed to be responsible for the intense excitation of long wavelength ultraviolet at 466-535 nm. (C) 2011 Elsevier Inc. All rights reserved.