Refined structural studies on the fluorite-related polymorphs of sol-gel undoped and Eu-doped yttrium tantalates.

Compounds with the general formula REMO (RE = rare earth ions; M = Ta, Nb, Sb, Ru, Ir, Os, Re, .), crystallize as a fluorite-related structure, forming polymorphs with different space groups. The space group strongly depends on the RE and M ionic radii and processing conditions.

Red and near-infrared emitting phosphors based on Eu- or Nd-doped lanthanum niobates prepared by the sol-gel route.

We have evaluated the structural and luminescence properties of Eu- or Nd-doped lanthanum niobate systems synthesized a sol-gel route and containing different dopant contents. XRD analysis revealed that the orthorhombic LaNbO and monoclinic LaNbO crystalline phases were present in all the samples, regardless of the dopant concentration. The excitation spectra of the samples displayed a broad band due to Nb→O charge transfer; this band was quite sensitive to the increasing Eu content.

Phase-sensitive radioluminescence and photoluminescence features in Tm-doped yttrium tantalates for cyan and white light generation.

Radioluminescence and visible photoluminescence tunability features from a single Tm-doped yttrium tantalate phosphor prepared by a soft sol-gel method designed to afford cubic YTaO and monoclinic M'-YTaO crystalline phases are reported. The annealing temperature influenced the crystallization kinetics and stabilized a preferential phase. To investigate how the crystalline phase affected the Tm optical properties, excitation and emission spectra in the visible range were recorded for the samples annealed at 900 or 1100 °C.