Crystal Structure, Electronic Structure, and Optical and Photoluminescence Properties of Eu(III) Ion-Doped Lu6Mo(W)O12

Lu6WO12 and Lu6MoO12 doped with Eu3+ ions have been prepared by using a citrate complexation route, followed by calcination at different temperatures. The morphology, structure, and optical and photoluminescence properties of the compounds were studied as a function of calcination temperature. Both compositions undergo transitions from a cubic to a hexagonal phase when the calcination temperature increases. All the compositions have strong absorption of near-UV light and show intense red luminescence under a near-UV excitation, which is related to the transfer of energy from the host lattices to dopant Eu3+ ions. Density functional theory calculations have also been performed. The calculation reveals that hexagonal Lu6WO12 and Lu6MoO12 are indirect bandgap materials, and the near-UV excitations are due to the electronic transitions from the O-2p orbitals to W-5d and Mo-4d orbitals, respectively. The lattice parameters and bandgap energies of hexagonal Lu6WO12 and Lu6MoO12 were determined.