RESUMEN
The organic/inorganic La1-xLnxH(O3PCH3)2 (Ln = Eu, Tb) hybrids have been synthesized by hydrothermal synthesis. The crystal structure of LaH(O3PCH3)2 consists of chains of edge-sharing LaO8 polyhedra linked through PO3C tetrahedra. Photoluminescence of Eu(3+), Tb(3+) and Eu(3+)/Tb(3+) co-doped materials have been investigated. The Eu and Tb hybrids show no concentration quenching versus doping rate suggesting energy migration through a percolation model. The Eu hybrids exhibit a red emission while the Tb ones exhibit, with the Tb rate increasing, a blue to green emission under a 378 nm excitation wavelength and a cyan to green emission under a 262 nm excitation wavelength. The doping rate dependent red shift results from a cross relaxation phenomenon between closed Tb(3+) ions. The blue to cyan shift observed for the slightly doped materials, when excitation wavelength shifts from 378 nm to 262 nm, is due to different relaxation phenomena, from the (5)D3 level for a 378 nm excitation wavelength and from the (5)D4 level via the 4f5d level for a 262 nm excitation wavelength. Under a 378 nm wavelength, the co-doped La0.93Eu0.03Tb0.04H(O3PCH3)2 hybrid exhibits a white/cyan emission with CIE coordinates equal to x = 0.29, y = 0.37.
RESUMEN
A new aluminate Sr33Bi(24+delta)Al48O(141+3delta/2), having an F3m cubic structure (a = 25.090 angstroms, Z = 4) and forming a close packed face centered cubic array of "Al84" fullerene geometry, has been discovered. This original structure consists of corner-sharing AlO4 tetrahedra forming "Al84O106" cubic units whose assemblage delimits five types of cages, three of them being empty, one being occupied by strontium, and the fifth one forming the huge spheric fullerene-type cavity. In the latter, strontium, oxygen, and bismuth ions form concentric spheres, with an onion-skin-like configuration. The latter ions are disposed into a compact "Bi16O(52-n[]n)" anion whose the exceptional geometry is characterized by a strong stereoactivity of the 6s2 lone pair of Bi3+.
RESUMEN
A new mixed-valent monophosphate Sr(2)V(2)O(PO(4))(3) has been synthesized. Its 4-fold superstructure has been refined using the 4D formalism for modulated structures and using X-ray single-crystal diffraction data. The average structure can be described as a stacking of [V(2)P(3)O(13)](infinity) layers and [Sr(2)](infinity) layers. In these layers, the VO(6) octahedra, occupied by V(III), the VO(5) trigonal bipyramids, occupied by V(IV), and the PO(4) tetrahedra form chains running along b. The 4D description allows us to give a better description of the measured intensities in reciprocal space (main and first order satellite reflections) and particularly to explain why the second order satellite reflections are not observed using a classical X-ray source. The corresponding structural mechanism consists of an alternation of disordered ribbons of VO(5) bipyramids and PO(4) tetrahedra in two enantiomorphic configurations, separated by displacively modulated ribbons of VO(6) octahedra and PO(4) tetrahedra. Crystal data: monoclinic, superstructure space group P2(1)/c, Z = 8, a = 17.389(1) Å, b = 5.094(1) Å, c = 30.032(4) Å, beta = 132.17(1) degrees; superspace group P2(1)/m(0,0,(1)/(4))0s, Z = 2, c' = c/4.
