Sophie Boudin

Remarkable thermal stability of Eu(4-phosphonobenzoate): structure investigations and luminescence properties

A new 3D rare-earth hybrid material Eu(p-O(3)PC(6)H(4)COO) has been synthesised by a hydrothermal route from Eu(NO(3))(3) x 5 H(2)O and the rigid precursor, 4-phosphonobenzoic acid. The structure of Eu(p-O(3)PC(6)H(4)COO) has been solved by X-ray diffraction on a powder sample and is described as an inorganic network in which both carboxylic and phosphonic acid groups are linked to Eu ions forming a three-dimensional architecture. Thermal analysis performed on this compound has underlined its remarkable stability up to 510 degrees C and an optical study has been conducted to examine its luminescence properties that have been related to the structure of the material. The structural and luminescence properties have also been compared with the related material Eu phenylphosphonate.

A crystal chemical approach to tuning of emission properties in rare earth doped ternary niobates

The photoluminescence (PL) properties of two Dy3+ doped ternary niobates, LaNbO4 and CaNb2O6 with fergusonite and columbite structures, respectively are investigated and compared. When the emission line corresponding to electric dipole transition of Dy3+ at 574 nm is monitored, an intense band due to host excitation is observed in both LaNbO4:Dy3+ CaNb2O6:Dy3+ systems indicating host-to-activator energy transfer. The presence of a host emission band at 250–300 nm range under 574 nm excitation indicates that the energy transfer is incomplete. The presence of host lattice emission plays an important role in determining the intensity and spectral response of the phosphor compositions.

Two new diphosphates with SrV2(P2O7)2 structure: mercury and lead phases

Two new diphosphates of the AV2(P2O7)2 series involving a trans configuration of the bidentate P2O7 groups have been synthesized for A = Hg or Pb. Their structure, determined from a single-crystal X-ray diffraction study is similar to that of the Sr-phase. They crystallize in the P space group, Z= 1, a= 4.848(1)A, b= 6.892(1)A, c= 8.077(2)A, α= 92.65(1)°, β= 93.26(1)°, γ= 106.23(1)°, for the Hg phase and a= 4.804(1)A, b= 7.113(1)A, c= 7.898(2)A, α= 89.78(1)°, β= 92.62(1)°, γ= 106.10(2)°, for the Pb phase. The crystal structures, solved by the heavy-atom method, were refined. The final agreement factors are R= 0.027 and 0.033 for the Hg and Pb phases, respectively.A comparison with the other isotypic members of this series A = Sr, Cd and NaxMoP2O7(0.25 < x < 0.50) is presented. The great similarity between the lead and strontium phases is shown, demonstrating the absence of a lone-pair effect of PbII in this structure. The particular behaviour of the Hg phase is emphasized, due to the ability of this element to adopt the dumbbell (or 2 + 4) coordination; the strong covalent character of HgII induces a significant distortion of the PO4 tetrahedra, rarely observed to date in transition-metal phosphates.

(NH4)2(VO)(VP)O7, a Layered Structure Comprising Tetrahedral VPO7 Groups

The new mixed-valence ammonium vanadophosphate (NH 4 ) 2 (VO)(VP)O 7 (diammonium phosphorus divanadium octaoxide) is isostructural with K 2 VO(X 2 O 7 ) (X = P, V). Its structure consists of [V 2 PO 8 ]∞layers of corner-sharing VO 5 pyramids and VPO 7 groups, interleaved with NH 4 + ions. The unusual features of this structure are the existence of the VPO 7 groups involving VO 4 and PO 4 tetrahedra, and the simultaneous presence of V IV O 5 and V V O 4 polyhedra, observed here for the first time in this class of compounds. The VPO 7 groups are statistically distributed in the framework. Magnetic measurements and bond-valence calculations confirm the mixed-valence character of this phase and show that the VO 5 pyramids and VO 4 tetrahedra are occupied by V IV and V V , respectively.

CaV2O(PO4)2, isotypic with the Cd phase

The new V III monophosphate, calcium divanadium oxodiphosphate, CaV 2 O(PO 4 ) 2 , is isotypic with the Cd phase. Its structure consists of [V 2 PO 7 ]∞ layers, built up from [VO 4 ]∞ rutile chains and [VPO 8 ]∞ chains, interconnected through PO 4 tetrahedra. This framework delimits tunnels running along (011), at the intersection of which the calcium ions are located in a «6 + 1» coordination mode

Mixed (Sr1−xCax)33Bi24Al48O141 fullerenoids: the defect structure analysed by (S)TEM techniques

Abstract (Sr1−xCax)33Bi24+∂Al48O141+3∂/2 fullerenoid solid solutions have been synthesized and the effect of partial substitution of Sr by Ca has been characterized by (scanning) transmission electron microscopy, applying different imaging methods. Most of the defects commonly observed in face centered cubic compounds, have also been observed in (Sr1−xCax)33Bi24+∂Al48O141+3∂/2. Based on purely geometrical and topological models, structural presentations for the coherent twin boundaries and stacking faults have been constructed on the basis of complex spherical “(Al84O210”) units. The results are compared to defects observed in the crystallite fullerite C60.

New Barium Antimony Aluminates evidenced by TEM techniques

Due to their structural diversity and chemical stability, the aluminates are widely used for various applications as for example sorption, exchange, catalysis, luminescence or transparent conducting properties [1]. The characterization of original and complex frameworks of new aluminates could be limited because most of these compounds are only obtained in the form of polycrystalline samples. After the discovery of the first fullerenoid oxide [1-3] (complex alkaline earth bismuth aluminates), we decide to investigate the Ba/Sb/Al/O system towards new aluminate frameworks. Characterizations were carried out by combining electron microscopy and X-Ray powder diffraction techniques. The ab initio structural studies of new the phases were realized by determining first the cationic ratios by EDS analyses, the cell parameters and the space group by ED and secondly the crystal structure by X Ray powder diffraction. Then the crystal structure was comforted by comparison between the simulated and experimental HREM images. We present here the new aluminates Ba1.5SbAl5O11.5 [4] (Figures 1,2) and Ba4Sb8Al16O44 (Figure 3). The first Ba1.5+xSbAl5O11.5 oxide crystallizes in an hexagonal cell (P63/mmc, a = b = 5.664 A, c = 32.159 A). Its structure consists of a stacking of different layers, noted M, K and P. The M layer is a mixed layer containing SbO6 octahedra and AlO4 tetrahedra. The K layer is a Kagome layer made of AlO6 octahedra. In the P layer, “pillars” are built from Al2O7 groups. The Ba 2+ ions lie between the pillars of the P layer and between two successive M layers. The second oxide, Ba4Sb8Al16O44 adopts a Hollandite structure type with SbOx and AlOx polyhedra, forming double rutile chains with oxygen vacancies. The ordering of Sb and Al atoms within the rutile chains induced a tripling of the c parameter. The Ba 2+ ions are located inside the tunnels, parallel to the c direction, on two split sites. These characterizations of the present Barium Antimony Aluminates evidenced 2D and 1D structures where ionic mobility, insertions, exchanges can be expected. The studies of such properties will be undertaken.

Mixed (Sr1−xCax)33Bi24Al48O141fullerenoids: the defect structure analysed by (S)TEM techniques: Dedicated to Professor Dr. Knut Urban on the occasion of his 65th birthday

Abstract (Sr1−xCax)33Bi24+∂Al48O141+3∂/2 fullerenoid solid solutions have been synthesized and the effect of partial substitution of Sr by Ca has been characterized by (scanning) transmission electron microscopy, applying different imaging methods. Most of the defects commonly observed in face centered cubic compounds, have also been observed in (Sr1−xCax)33Bi24+∂Al48O141+3∂/2. Based on purely geometrical and topological models, structural presentations for the coherent twin boundaries and stacking faults have been constructed on the basis of complex spherical “(Al84O210”) units. The results are compared to defects observed in the crystallite fullerite C60.

Mixed (Sr_{1-x}Ca_{x})_{33}Bi_{24}Al_{48}O_{141} fullerenoids: the defect structure analysed by (S)TEM techniques

Abstract (Sr1−xCax)33Bi24+∂Al48O141+3∂/2 fullerenoid solid solutions have been synthesized and the effect of partial substitution of Sr by Ca has been characterized by (scanning) transmission electron microscopy, applying different imaging methods. Most of the defects commonly observed in face centered cubic compounds, have also been observed in (Sr1−xCax)33Bi24+∂Al48O141+3∂/2. Based on purely geometrical and topological models, structural presentations for the coherent twin boundaries and stacking faults have been constructed on the basis of complex spherical “(Al84O210”) units. The results are compared to defects observed in the crystallite fullerite C60.

CdV2(P2O7)2

Cadmium vanadium diphosphate, CdV 2 (P 2 O 7 ) 2 , is isotypic with AV 2 (P 2 O 7 ) 2 (A=Ca, Sr) and Na x MoP 2 O 7 (0.25<x<0.50). Its structure consists of similar [VP 4 O 14 ]∞ columns which are built up from VO 6 octahedra and P 2 O 7 pyrophosphate groups, and linked together through VO 6 octahedra. This framework delimits tunnels in which the Cd ions are located with octahedral coordination. A comparison with AV 2 (P 2 O 7 ) 2 (A=Ca, Sr) is given