Structural, vibrational study and UV photoluminescence properties of the system Bi(2−x)Lu(x)WO6 (0.1 ≤ x ≤ 1)

The bismuth lutetium tungstate series Bi (2− x ) Lu ( x ) WO 6 with 0.1 ≤ x ≤ 1 were synthesized by solid state reaction of oxide precursors at 1000 °C for 3 h. The as-prepared polycrystalline compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and photoluminescence (PL) analyses. Biphasic samples were obtained in the composition range of 0.1 ≤ x ≤ 0.3. Solid solutions were obtained in the composition range of 0.4 ≤ x ≤ 1, and their monoclinic crystal structure was refined using the Rietveld method. SEM micrographs showed that solid solutions presented homogeneous morphologies. Attributions of Raman vibrational modes were proposed. A shift in the vibrational wavenumber depending on the lutetium composition was observed. The specific broadening of the spectral bands was interpreted in terms of long range Bi/Lu disorder and local WO 6 octahedron distortions in the structure. The PL experiments were performed under UV-laser light irradiation. Each PL band was decomposed into three Gaussian components with energies close to 1.25, 1.80 and 2.1 eV. Their integrated intensities increased with the value of x . The presence of the near infrared band at 1.25 eV is discussed. This study on bismuth lutetium tungstates presents, for the first time, correlations between structure, vibrational and photoluminescence properties in the case of solid solutions Bi 2− x Lu x WO 6 . The origin of luminescence signals under UV excitation is discussed.