Synthesis, structural characterization and luminescent properties of Tb3+-doped AgLaP2O7 phosphors

The unit cell parameters and the space group of all the family members were determined by PXRD data. The compounds crystallize in the orthorhombic Pnma space group, with the AgLaP2O7 cell constants equal to: a = 8.6706(1) angstrom, b = 5.3218(1) angstrom, c = 12.8839(1) angstrom and cell volume V = 594.51(1) angstrom(3). A decreasing trend for unit cell parameters was observed at increase of dopant concentration. For the pure phase, the investigation was completed with the structure solution via Direct Methods and Rietveld refinement. The crystal structure consists of compact layers of LaO9 polyhedra, down the c axis, bridged by P2O7 diphosphate groups and by zig-zag chains of AgO9 polyhedra down b.

Silver lanthanum diphosphates doped with terbium, AgLa1-xTbxP2O7 (x=0%, 1%, 5%, 10%, 15% and 20%), were prepared by solid state reaction at T = 500 degrees. The obtained compounds were investigated by means of a multi-methodological approach, involving the Scanning Electron Microscopy (SEM) equipped with energy dispersive X-Ray spectroscopy (EDS) for morphological investigation and semi-quantitative chemical analysis, respectively; powder X-ray diffraction (PXRD) for structural characterization and Rietveld refinement; Fourier Transform InfraRed (FTIR) and Raman spectroscopies for qualitative study. Finally, emission spectra were collected in order to detect the fluorescence properties of the compounds.