Electronic, structural, and optical properties of Y2WO6, a host material for inorganic phosphors

Abstract

Optimization by first principles DFT-based electronic structure methods of the crystal structures for the five polymorphs of Y2WO6 reported in the literature yields results in good agreement with those determined experimentally by X-ray diffraction. The monoclinic P2/c phase appears to be the most stable one at ambient conditions, although high temperature orthorhombic phases with larger molar volumes could be favoured upon replacement of Y3þ cations by larger Ln3þ ones, and hence, provide plausible structures for Y2WO6:Ln3þ phosphors at ambient conditions. For all polymorphs the top of the valence band is dominated by O2p orbitals with a relatively narrow WO6-centred conduction band appearing just below a broad Y4d-centred band. Insertion energies for Eu3þ replacing Y3þ are estimated to be in the range of 3e4eV per cation, with the smaller values corresponding to substitutions into the larger octacoordinated Y3þ sites.