Synthèse et caractérisation physico-chimique de nouveaux phosphates de magnésium : (A¹₂ ou B²)Mg₂M³(PO₄)₃ (A = Na, Ag ; B = Ca, Pb, Sr, Ba ; M = Fe, In)

Thèse sous embargo de l’auteur jusqu’au 29-11-2022. Pour les membres de la communauté universitaire (hors UPHF), ce document est accessible via le Prêt entre bibliothèques (s’adresser à votre bibliothèque universitaire).This study is a part of contribution to the investigation program aiming to elaborate and to characterize new phosphate-based materials, particularly, with the alluaudite and/or α- CrPO₄ type structure. These compounds are characterized by their wide physico-chemical properties that they can exhibit in several fields of application such as catalysis and electrochemistry.We have isolated and determined the structure of eleven new phosphates by means of single crystal X-ray diffraction.The phosphate PbMg₃(HPO₄)(PO₄)₂ was synthesized by hydrothermal method. Its structure was resolved in monoclinic system with space group I2/m.The substitution of one cation Mg²⁺ by Fe³⁺ has allowed us to isolate five new compounds using solid-state diffusion method. Four compounds of general formula MMg₂Fe(PO₄)₃ (M = Ba, Sr, Pb, Ca) exhibit two different structural types. The Sr or Ba based compounds are related to the α-CrPO₄ type structure and crystallize with the space group Imma of the orthorhombic system. Besides, the Ca or Pb based phosphates crystallize with the P21/n space group of the monoclinic system. The fifth phase, namely Ca₂MgFe₂(PO₄)₄, crystallizes in orthorhombic system with a Pbca space group.Finally, we have succeeded to synthesize five new Mg, Fe and monovalent elements based phosphates, namely NaMg₃(HPO₄)₂(PO₄), Na₂Mg₂Fe(PO₄)₃, Ag₁,₆₇Mg₂,₃₃Fe₀,₈₉(PO₄)₃, Na₁,₈₅Mg₁,₈₅In₁,₁₅(PO₄)₃ and Ag₁,₆₉Mg₁,₆₉In₁,₃₁(PO₄)₃, using both the hydrothermal and the solid-state diffusion methods. All these phosphates crystallize in the monoclinic system with C2/c space group and are similar to the alluaudite type structural. The powder of stoichiometric compounds A₂Mg₂Fe(PO₄)₃ (A = Na, Ag) were synthesized by solid-state method and characterized by X-Ray powder diffraction. Conductivity’s studies by impedance spectroscopic method have allowed determining values for Na₂Mg₂Fe(PO₄)₃ (σ = 0.12.10⁻⁴ S.cm⁻¹ at 500°C) and for Ag₂Mg₂Fe(PO₄)₃ (σ = 4.10⁻³ S.cm⁻¹ at 500°C) due to cations migration in the channels of the structure.Ce travail de thèse s’inscrit dans le cadre de la contribution au programme de valorisation des matériaux phosphatés et plus particulièrement, les phosphates de type alluaudite ou α-CrPO₄. Ces composés se distinguent par leurs propriétés physico-chimiques aussi variées qu’importantes et sont très convoités dans plusieurs domaines d’applications comme la catalyse et l’électrochimie.Nous avons pu isoler onze nouveaux phosphates et déterminer leur structure par la diffraction des rayons X sur monocristal.Le phosphate PbMg₃(HPO₄)(PO₄)₂ a été préparé par la méthode hydrothermale. Sa structure cristalline a été résolue dans le système monoclinique I2/m.La substitution d’un cation Mg²⁺ par un fer trivalent (Fe³) dans le composé PbMg₃(HPO₄)(PO₄)₂ a permis d’isoler cinq nouveaux composés par voie solide. Quatre phosphates de formule MMg₂Fe(PO₄)₃ (M = Ba, Sr, Pb, Ca) s’apparentent à deux types structuraux différents. Les composés contenant Sr et Ba sont de type α-CrPO₄ et cristallisent dans une maille orthorhombique de groupe d’espace Imma. Quant à ceux contenant Ca ou Pb, leur structure s’affine dans le groupe d’espace P21/n du système monoclinique. Le cinquième phosphate est de formule Ca₂MgFe₂(PO₄)₄ cristallisant dans le système monoclinique avec un groupe d’espace Pbca.Enfin, nous avons synthétisé cinq nouveaux phosphates à base de Mg, de Fe et d’élément monovalents : NaMg₃(HPO₄)2(PO₄), Na₂Mg₂Fe(PO₄)₃, Ag₁,₆₇Mg₂,₃₃Fe₀,₈₉(PO₄)₃, Na₁,₈₅Mg₁,₈₅In₁,₁₅(PO₄)₃ et Ag₁,₆₉Mg₁,₆₉In₁,₃₁(PO₄)₃, en utilisant aussi bien la méthode hydrothermale que la synthèse par voie solide. Ces phosphates cristallisent dans le système monoclinique de groupe d’espace C2/c et s’apparentent au type structural alluaudite. La poudre cristalline des phases stoechiométriques A₂Mg₂Fe(PO₄)₃ (A = Na, Ag) a été synthétisée par voie solide et caractérisée par la diffraction de rayons X sur poudre. L’étude de la conductivité en fonction de la température de ces deux composés conduit à σ = 0,12x10⁻⁴ S.cm⁻¹ pour Na₂Mg₂Fe(PO₄)₃ et à σ = 4x10⁻³ S.cm⁻¹ pour Ag₂Mg₂Fe(PO₄)₃ à 500°C

Synthesis and physicochemical characterization of new magnesium phosphates : (A¹₂ ou B²)Mg₂M³(PO₄)₃ (A = Na, Ag ; B = Ca, Pb, Sr, Ba ; M = Fe, In)

Ce travail de thèse s’inscrit dans le cadre de la contribution au programme de valorisation des matériaux phosphatés et plus particulièrement, les phosphates de type alluaudite ou α-CrPO₄. Ces composés se distinguent par leurs propriétés physico-chimiques aussi variées qu’importantes et sont très convoités dans plusieurs domaines d’applications comme la catalyse et l’électrochimie.Nous avons pu isoler onze nouveaux phosphates et déterminer leur structure par la diffraction des rayons X sur monocristal.Le phosphate PbMg₃(HPO₄)(PO₄)₂ a été préparé par la méthode hydrothermale. Sa structure cristalline a été résolue dans le système monoclinique I2/m.La substitution d’un cation Mg²⁺ par un fer trivalent (Fe³) dans le composé PbMg₃(HPO₄)(PO₄)₂ a permis d’isoler cinq nouveaux composés par voie solide. Quatre phosphates de formule MMg₂Fe(PO₄)₃ (M = Ba, Sr, Pb, Ca) s’apparentent à deux types structuraux différents. Les composés contenant Sr et Ba sont de type α-CrPO₄ et cristallisent dans une maille orthorhombique de groupe d’espace Imma. Quant à ceux contenant Ca ou Pb, leur structure s’affine dans le groupe d’espace P21/n du système monoclinique. Le cinquième phosphate est de formule Ca₂MgFe₂(PO₄)₄ cristallisant dans le système monoclinique avec un groupe d’espace Pbca.Enfin, nous avons synthétisé cinq nouveaux phosphates à base de Mg, de Fe et d’élément monovalents : NaMg₃(HPO₄)2(PO₄), Na₂Mg₂Fe(PO₄)₃, Ag₁,₆₇Mg₂,₃₃Fe₀,₈₉(PO₄)₃, Na₁,₈₅Mg₁,₈₅In₁,₁₅(PO₄)₃ et Ag₁,₆₉Mg₁,₆₉In₁,₃₁(PO₄)₃, en utilisant aussi bien la méthode hydrothermale que la synthèse par voie solide. Ces phosphates cristallisent dans le système monoclinique de groupe d’espace C2/c et s’apparentent au type structural alluaudite. La poudre cristalline des phases stoechiométriques A₂Mg₂Fe(PO₄)₃ (A = Na, Ag) a été synthétisée par voie solide et caractérisée par la diffraction de rayons X sur poudre. L’étude de la conductivité en fonction de la température de ces deux composés conduit à σ = 0,12x10⁻⁴ S.cm⁻¹ pour Na₂Mg₂Fe(PO₄)₃ et à σ = 4x10⁻³ S.cm⁻¹ pour Ag₂Mg₂Fe(PO₄)₃ à 500°C.This study is a part of contribution to the investigation program aiming to elaborate and to characterize new phosphate-based materials, particularly, with the alluaudite and/or α- CrPO₄ type structure. These compounds are characterized by their wide physico-chemical properties that they can exhibit in several fields of application such as catalysis and electrochemistry.We have isolated and determined the structure of eleven new phosphates by means of single crystal X-ray diffraction.The phosphate PbMg₃(HPO₄)(PO₄)₂ was synthesized by hydrothermal method. Its structure was resolved in monoclinic system with space group I2/m.The substitution of one cation Mg²⁺ by Fe³⁺ has allowed us to isolate five new compounds using solid-state diffusion method. Four compounds of general formula MMg₂Fe(PO₄)₃ (M = Ba, Sr, Pb, Ca) exhibit two different structural types. The Sr or Ba based compounds are related to the α-CrPO₄ type structure and crystallize with the space group Imma of the orthorhombic system. Besides, the Ca or Pb based phosphates crystallize with the P21/n space group of the monoclinic system. The fifth phase, namely Ca₂MgFe₂(PO₄)₄, crystallizes in orthorhombic system with a Pbca space group.Finally, we have succeeded to synthesize five new Mg, Fe and monovalent elements based phosphates, namely NaMg₃(HPO₄)₂(PO₄), Na₂Mg₂Fe(PO₄)₃, Ag₁,₆₇Mg₂,₃₃Fe₀,₈₉(PO₄)₃, Na₁,₈₅Mg₁,₈₅In₁,₁₅(PO₄)₃ and Ag₁,₆₉Mg₁,₆₉In₁,₃₁(PO₄)₃, using both the hydrothermal and the solid-state diffusion methods. All these phosphates crystallize in the monoclinic system with C2/c space group and are similar to the alluaudite type structural. The powder of stoichiometric compounds A₂Mg₂Fe(PO₄)₃ (A = Na, Ag) were synthesized by solid-state method and characterized by X-Ray powder diffraction. Conductivity’s studies by impedance spectroscopic method have allowed determining values for Na₂Mg₂Fe(PO₄)₃ (σ = 0.12.10⁻⁴ S.cm⁻¹ at 500°C) and for Ag₂Mg₂Fe(PO₄)₃ (σ = 4.10⁻³ S.cm⁻¹ at 500°C) due to cations migration in the channels of the structure

Na1.85Mg1.85In1.15(PO4)3 and Ag1.69Mg1.69In1.31(PO4)3 with alluaudite-type structures

Single crystals of two new phosphates, sodium magnesium indium(III) tris(orthophosphate) and silver magnesium indium(III) tris(orthophosphate), were obtained from solid-state reactions. The two phosphates are isotypic and exhibit alluaudite-type structures. They are characterized by a cationic disorder of the Mg and In sites and a partial occupation of the Na and Ag sites, respectively. The structure of both phosphates is made up of chains of edge-sharing [(Mg,In)O6] octahedra extending parallel to [10\overline{1}]. Adjacent chains are linked by PO4 tetrahedra to form a three-dimensional framework delimiting two types of channels parallel to [001] in which the monovalent cations are situated. The coordination numbers of the Na+ cations are 6 and 8, and for both Ag+ cations 6. The corresponding coordination spheres are considerably distorted

Crystal structure of alluaudite-type NaMg3(HPO4)2(PO4)

The title compound, sodium trimagnesium bis(hydrogen phosphate) phosphate, was obtained under hydrothermal conditions. In the crystal, two types of [MgO6] octahedra, one with point group symmetry 2, share edges to build chains extending parallel to [10-1]. These chains are linked together by two kinds of phosphate tetrahedra, HPO4 and PO4, the latter with point group symmetry 2. The three-dimensional framework delimits two different types of channels extending along [001]. One channel hosts the Na+ cations (site symmetry 2) surrounded by eight O atoms, with Na—O bond lengths varying between 2.2974 (13) and 2.922 (2) Å. The OH group of the HPO4 tetrahedron points into the other type of channel and exhibits a strong hydrogen bond to an O atom of the PO4 tetrahedron on the opposite side

Two novel phosphates Na2Mg2Fe(PO4)3 and Ag2Mg2Fe(PO4)3 with alluaudite structure: Synthesis, crystal structure and electrical properties

International audienc

Synthesis, crystal structure and magnetic behavior of a new calcium magnesium and iron orthophosphate Ca2MgFe2(PO4)4

International audienceThe structure of the new calcium magnesium iron orthophosphate, Ca2MgFe2(PO4)4 was determined from single crystal X-ray diffraction data. It crystallizes in the orthorhombic system, space group Pbca, with all atoms in general positions among which two sites are disordered. The crystal structure of this phosphate is build up from PO4 tetrahedra linked to FeO6 octahedra and to (Fe/Mg)O5 polyhedra via common vertices. In fact, each of the two mixed sites (Fe/Mg) is surrounded by five oxygen atoms which form either a pyramid with a square base or a bi-pyramid with a triangular base. The interconnection of these polyhedra leads to a three-dimensional structure delimiting cavities where Ca2+ cations are localized. The powder of this compound was successfully obtained by solid state reaction and its X-ray diffraction diagram was refined by pattern matching method. The magnetic measurements show multiple transition assigned to frustrated triangles locally present in AFM (antiferromagnetic) magnetic layered units