Single Crystal Structure of the Divalent Europium Chloroapatite Eu 5 (PO 4 ) 3 Cl

The chloroapatite Eu 5 (PO 4 ) 3 Cl has been synthesized by a solid-state reaction route using a salt flux. Its structure has been solved and refined from single crystal X-ray data: apatite type, P6 3 /m, a = 988.36(4), c = 720.32(3) pm, Z = 2, R(F) = 0.021 and wR(F 2 ) = 0.063 for 748 unique reflections and 40 variables. The Eu 5 (PO 4 ) 3 Cl structure contains isolated (PO 4 ) 3− tetrahedra and two crystallographically independent divalent europium sites. The Eu1 2+ ion at the 4 f position is located in a distorted tri-capped trigonal prism whereas the Eu2 2+ ion at the 6h position is located in a strongly distorted square anti-prism. The chloride ions have octahedral europium coordination (307 pm Eu-Cl)

non disponible

Contrary to their homologous LiMPO4 (M: transition metal) which crystallize with the olivine type structure, the vanadates LiMVO4 crystallize with the spinel type structure or Na2CrO4 type structure. In general, few compounds crystallize with this last structural type. This is due to the strong steric constraints existing within this structure. Thus the study of the substitution of cadmium for lithium in the LiCdVO4 compound highlighted the existence of modulated structures for compositions (Li1 xCdx/2)CdVO4 (0,4 In order to extend our comprehension of the structural differences between phosphates and vanadates of general formula AA' BO4 (A : alkali and d10 cation, A' : transition metal, B : P et V), the AMnPO4 and AMnVO4 series were studied and this made it possible to synthesize and characterize the new AMnVO4 compounds with A: Cu, Na, Ag, K, Rb and AMnPO4 with A: Rb and Ag. A very surprising result was obtained with the new compound KMnVO4, which crystallizes in a new oxygen-deficient perovskite type structure.Contrairement à leurs homologues LiMPO4 (M : métal de transition) de structure olivine, les vanadates LiMVO4 cristallisent avec des structures type spinelle ou Na2CrO4. De façon générale, peu de composés cristallisent avec ce dernier type structural car de fortes contraintes stériques existent au sein de cette structure. Ainsi l'étude de la substitution du cadmium au lithium dans le composé LiCdVO4 a mis en évidence l'existence de structures modulées pour des compositions (Li1 xCdx/2)CdVO4 (0,4 L'étude du système homologue au sodium (Na1xCdx/2)CdVO4 (0 ≤ x ≤ 1) n'a pas permis d'isoler des phases modulées. La substitution du sodium au cadmium engendre de fortes contraintes stériques qui sont à l'origine d'une transition structurale de la structure type Na2CrO4 à la structure maricite. Cette transition a permis d'étendre le système jusqu'au composé limite (Cd1/2)CdVO4 (x = 1).Afin d'étendre notre compréhension des différences structurales entre les phosphates et les vanadates de formule générale AA'BO4 (A : alcalin et cation d10, A' : métal de transition, B : P et V), les séries AMnPO4 et AMnVO4 ont été étudiées et ceci a permis de synthétiser et caractériser les nouveaux composés AMnVO4 avec A : Cu, Na, Ag, K, Rb et AMnPO4 avec A : Rb et Ag. Un résultat surprenant a été obtenu avec le nouveau composé KMnVO4 qui cristallise avec une structure de type pérovskite déficitaire en oxygène

Synthesis, structures and magnetic properties of the new vanadates AgMnVO4 and RbMnVO4

The new compounds, AgMnVO4 and RbMnVO4 have been synthesized by solid state reaction route. Their crystal structures were determined from single-crystal X-ray diffraction data for RbMnVO4 and powder X-ray diffraction data for AgMnVO4. AgMnVO4 crystallizes with the maricite-type structure in space group Pnma, a=9.5778(6) Å, b=6.8518(4) Å, c=5.3734(3) Å and Z=4. RbMnVO4 crystallizes in space group P63 with a stuffed tridymite-type structure, a=11.2584(3), c=8.9893(13) Å and Z=8. A merohedral twinning was taken into account for its structural refinement. To our knowledge this is the first vanadate showing this structural type. AgMnVO4 and RbMnVO4 were characterized by magnetic susceptibility and specific heat measurements. AgMnVO4 is antiferromagnetic with a Néel temperature of 12.3 K determined by specific heat measurements. RbMnVO4 exhibits canted antiferromagnetism with a Néel temperature of 6.5 K

Crystal structure of the new phosphate AgMnPO₄

The new compound AgMnPO4 has been synthesized by a solid-state reaction route. Its crystal structure was determined from single-crystal X-ray diffraction data..

Crystal structures of new pyrovanadates A2MnV2O7 (A = Rb, K)

The new compounds A2MnV2O7 (A = K, Rb) with structures related to the melilite-type have been synthesized by a solid state reaction route. The crystal structures of K2MnV2O7, Rb2MnV2O7 and KRbMnV2O7 have been determined using X-ray single crystal diffraction data..

Structure and magnetic properties of the new phosphates RbMnPO4

The new compound RbMnPO4 has been synthesized using a solid state route. Its structure has been determined at room temperature by Rietveld refinement of X-ray powder diffraction data. The space group is P21 with the cell parameters a = 8.9476(3), b = 5.4511(2), c = 9.1655(3) Å and β = 90.2912(8)°. The framework of RbMnPO4 has the same topology as that of zeolite ABW-type structures..

Sodium calcium orthovanadate, NaCa4(VO4)3

Single crystals of sodium tetracalcium trivanadium dodecaoxide were prepared by melting a powder sample of NaCa4(VO4)3 at 1673 K, followed by slow cooling to room temperature..

Crystal structures of new pyrovanadates A2MnV2O7 (A = Rb, K)

The new compounds A2MnV2O7 (A = K, Rb) with structures related to the melilite-type have been synthesized by a solid state reaction route. The crystal structures of K2MnV2O7, Rb2MnV2O7 and KRbMnV2O7 have been determined using X-ray single crystal diffraction data..