X-ray Thermodiffractometry Research Articles

Synthesis, characterisation and luminescent properties of a new three-dimensional lanthanide trimesate: M((C6H3)–(CO2)3) (M = Y, Ln) or MIL-78

A new three-dimensional europium-doped yttrium 1,3,5-benzenetricarboxylate has been obtained under hydrothermal conditions. The structure of MIL-78(Y, Eu) or Y1−xEux((C6H3)–(CO2)3) (x ∼ 0.024) has been solved from X-ray powder diffraction data (a = 6.941(1) Å, b = 14.700(2) Å, c = 8.488(1) Å, β = 107.73(1)°, V = 824.9(4) Å3, space group C2/m (no. 12)). Its structure is built up from chains of edged-sharing eight-coordinated monocapped square antiprism polyhedra and trimesate anions, creating a three-dimensional structure. The same structure is formed by replacing yttrium by a rare-earth element. The thermal behaviour of MIL-78(Y, Eu) has been investigated using TGA and X-ray thermodiffractometry and indicates that MIL-78(Y, Eu) is stable up to 450 °C. The study of the optical properties of samples doped with different rare-earths reveals strong fluorescence under VUV radiation.

Synthesis, structure determination and magnetic behaviour of the first porous hybrid oxyfluorinated vanado(iii)carboxylate: MIL-71 or Viii2(OH)2F2{O2C-C6H4-CO2}·H2O

A new type of three-dimensional vanadium(III) dicarboxylate, MIL-71 or VIII2(OH)2F2{O2C-C6H4-CO2}·H2O, has been obtained under hydrothermal conditions from aqueous mixtures of vanadium, 1,4-benzenedicarboxylic acid, and HF. MIL-71cal or VIV2O2F2{O2C-C6H4-CO2} is obtained by calcination of the parent compound in air at 250 °C. The three-dimensional structure of MIL-71 (S.G.: Cmmm; a = 21.4477(8) A, b = 7.1449(2) A, c = 3.8246(2) A, and Z = 2) consists of layers built from corner-sharing {VIIIO2(OH)2F2} octahedra connected by the terephthalate linkers. The role of fluorine in this structure is understood by comparison with the already known hybrid vanado(III)carboxylates. The thermal behavior of the two solids has been investigated using TGA and X-ray thermodiffractometry. Finally, magnetic measurements performed on both MIL-71 and MIL-71cal reveal a canted antiferromagnetic behavior with Neel temperatures below 20 K.

Polymorphism of Bi 1− xLn xO 1.5 phases (0< x

The Bi 1− x Ln x O 1.5 solid solutions (Ln=La, Pr, Nd), of the β 2/β 1/ε (Bi–Sr–O) structural type, have been investigated in their Ln-rich domains. For Ln=La, Pr, and Nd, the upper limits are 0.35, 0.35 and 0.33, respectively. The Bi 4Ln 2O 9 ε phase ( x=0.33) appears to be the single definite compound. For Bi 4La 2O 9, Bi 4Pr 2O 9 and Bi 4Nd 2O 9, the ε-type cells are respectively: a=9.484(4) Å, b=3.982(2) Å, c=7.030(3) Å, β=104.75(3)°; a=9.470(5) Å, b=3.945(2) Å, c=6.968(4) Å, β=104.73(3)° and a=9.439(3) Å, b=3.944(2) Å, c=6.923(2) Å, β=105.03(3)°. Upon heating, each monoclinic (ε) compound transforms successively into rhombohedral phases (β 2/β 1) and finally into a cubic fluorite-type phase. For La- and Pr-based compounds, all transitions are reversible; for Nd, depending on the thermal treatment, the reversibility of ε→β 2 can be incomplete. These transformations are characterized using X-ray thermodiffractometry, differential thermal analysis, dilatometry and impedance spectroscopy versus temperature. Examination of Bi 4(Ln, Ln′) 2O 9 samples allows to correlate the evolution of the thermal behavior and of the unit cell parameters, to the lanthanide size. A partial plot of the (Bi 2O 3) 1− x –(La 2O 3) x phase diagram (0≤ x≤0.40) is proposed.

Very large breathing effect in the first nanoporous chromium(III)-based solids: MIL-53 or Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)] x [HO(2)C-C(6)H(4)-CO(2)H](x) x H(2)O(y).

The first three-dimensional chromium(III) dicarboxylate, MIL-53as or Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)].[HO(2)C-C(6)H(4)-CO(2)H](0.75), has been obtained under hydrothermal conditions (as: as-synthesized). The free acid can be removed by calcination giving the resulting solid, MIL-53ht or Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)]. At room temperature, MIL-53ht adsorbs atmospheric water immediately to give Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)] x H(2)O or MIL-53lt (lt: low-temperature form, ht: high-temperature form). Both structures, which have been determined by using X-ray powder diffraction data, are built up from chains of chromium(III) octahedra linked through terephthalate dianions. This creates a three-dimensional structure with an array of one-dimensional large pore channels filled with free disordered terephthalic molecules (MIL-53as) or water molecules (MIL-53lt); when the free molecules are removed, this leads to a nanoporous solid (MIL-53ht) with a Langmuir surface area over 1500 m(2)/g. The transition between the hydrated form (MIL-53lt) and the anhydrous solid (MIL-53ht) is fully reversible and followed by a very high breathing effect (more than 5 A), the pores being clipped in the presence of water molecules (MIL-53lt) and reopened when the channels are empty (MIL-53ht). The thermal behavior of the two solids has been investigated using TGA and X-ray thermodiffractometry. The sorption properties of MIL-53lt have also been studied using several organic solvents. Finally, magnetism measurements performed on MIL-53as and MIL-53lt revealed that these two phases are antiferromagnetic with Néel temperatures T(N) of 65 and 55 K, respectively. Crystal data for MIL-53as is as follows: orthorhombic space group Pnam with a = 17.340(1) A, b = 12.178(1) A, c = 6.822(1) A, and Z = 4. Crystal data for MIL-53ht is as follows: orthorhombic space group Imcm with a = 16.733(1) A, b = 13.038(1) A, c = 6.812(1) A, and Z = 4. Crystal data for MIL-53lt is as follows: monoclinic space group C2/c with a = 19.685(4) A, b = 7.849(1) A, c = 6.782(1) A, beta = 104.90(1) degrees, and Z = 4.

Hydrothermal Synthesis, Structure Determination, and Thermal Behavior of New Three-Dimensional Europium Terephthalates: MIL-51LT,HT and MIL-52 or Eu2n(OH)x(H2O)y(O2C−C6H4−CO2)z (n = III, III, II; x = 4, 0, 0; y = 2, 0, 0; z = 1, 1, 2)

Three-dimensional europium terephthalates have been obtained under hydrothermal conditions and their structures solved using either X-ray powder diffraction or single-crystal data. MIL-51LT or Eu2III(H2O)2(OH)4(O2C−C6H4−CO2) and MIL-51HT or Eu2III(OH)4(O2C−C6H4−CO2) contain only trivalent europium, while MIL-52 or EuII(O2C−C6H4−CO2) involves only europium(II) metallic centers. Their structures are built up from eight- or nine-coordinated europium polyhedra and terephthalate anions, creating pillared structures. Inorganic layers of MIL-51LT,HT are closely related to those of europium hydroxide. Oxygen atoms of the inorganic sheets are either water molecules, hydroxyl groups, or oxygen atoms of the dicarboxylates. In the case of MIL-52, anions are oxygen atoms from the organic moities. In both structures, elongated hydrophobic channels are present but with no real porosity. Thermogravimetric analysis and X-ray thermodiffractometry have shown that MIL-51LT and MIL-51HT are correlated. Crystal data for MIL-51...

Hydrothermal synthesis, structure determination from powder data of a three-dimensional zirconium diphosphonate with an exceptionally high thermal stability: Zr(O3P-(CH2)-PO3) or MIL-57

Zr(O3P-(CH2)-PO3) or MIL-57 was prepared in a pure form under hydrothermal conditions (3 days, 493 K, autogenous pressure). Its structure was solved ab initio from laboratory powder X-ray diffraction data. This compound is monoclinic (space group P21 (no. 14)) with a = 7.589(1), b = 8.110(1), c = 5.056(1) A, β = 103.934(1)°, V = 302.14(1) A3 and Z = 2. Its three-dimensional structure is built up from zirconium(IV) octahedra linked together via diphosphonate groups. This delimits a three-dimensional network with three and seven-member-ring tunnels along the c axis. The thermal behaviour, deduced from TGA and X-ray thermodiffractometry has been investigated and reveals that MIL-57 is stable under air atmosphere up to 1023 K, which is the highest temperature reported to date for a hybrid inorganic–organic solid. A brief comparison between structures of MIL-57 and ZrP2O7 is also reported.

Hydrothermal synthesis, thermal behaviour and structure determination from powder data of a porous three-dimensional europium trimesate: Eu3(H2O)(OH)6[C6H3(CO2)3]·3H2O or MIL-63

A new three-dimensional microporous europium carboxylate has been obtained under hydrothermal conditions using trimesic acid and its structure solved from X-ray powder diffraction data. MIL-63 or Eu3(H2O)(OH)6[C6H3(CO2)3]·3H2O crystallises in monoclinic symmetry with a = 17.640(1), b = 3.689(2), c = 12.385(1) A, β = 91.245(1)°, V = 805.74(4) A3, space group P21 (no 4). Its structure is built up from nine-coordinate monocapped square antiprism europium polyhedra and trimesate anions, creating pillared structures. The inorganic layers of MIL-63 are similar to those of europium hydroxide, but with a periodic oscillation that leaves within the interlayer space two types of pores along the b axis that contain both free and bound water molecules. The thermal behaviour of MIL-63 has been investigated using TGA and X-ray thermodiffractometry, and indicates that MIL-63 is stable up to 723 K and exhibits zeolitic behaviour.

The layered perovskite K2SrTa2O7: hydration and K+/H+ ion exchange

We present a full characterization of the anhydrous layered material K2SrTa2O7 related to Ruddesden–Popper type phases. The unit cell, determined from powder X-ray diffraction, is tetragonal with a = 3.9858(1) A and c = 21.785(1) A (space group I4/mmm, Z = 2). The layered structure allows spontaneous water intercalation when the product is kept in air at ambient temperature. During hydration, a reversible structural transformation from an I to a P Bravais lattice is observed. By using K+/H+ ion exchange, in dilute HNO3 or in acetic acid, we obtained the protonated phase H2SrTa2O7·xH2O which is compared to the one synthesized from Li2SrTa2O7 previously reported by us. For both compounds, the hydration–dehydration behavior, studied by DTA/TGA and X-ray thermodiffractometry is discussed. In addition, we carried out an electron microscopy study of anhydrous K2SrTa2O7 by selected area electron diffraction (SAED).

A study of the Na 2O–CaO–P 2O 5–SiO 2 system with respect to the behaviour of phosphate bonded basic refractories at high temperature

Investigating various phosphate bonded basic refractories by means of powder X-ray diffraction, energy dispersive spectroscopy and X-ray fluorescence analyses, reveals a relation between good mechanical properties at high temperature and the presence of a silicophosphate bond ( T>1200°C). The silicophosphate formation mechanism was studied using X-ray thermodiffractometry. From room temperature up to 500°C, a mixed calcium sodium phosphate gel is formed. It transforms around 500°C into a crystalline calcium sodium phosphate which is not stable at room temperature. Above 1200°C, the silicophosphate belongs to a Na 2− x Ca 5+ x (PO 4) 4− x (SiO 4) x type solid solution with x>0 identified by studying the Na 2O–CaO–P 2O 5–SiO 2 system. The Na 2− x Ca 5+ x (PO 4) 4− x (SiO 4) x solid solution structure was shown to be a superstructure of the glaserite-type structure. Good mechanical properties of the refractory material are maintained as long as the silicophosphate glaserite-type unit cell superstructure is kept. That is achieved using starting raw materials with a high CaO SiO 2 ratio and a high calcium content.

Hydrothermal Synthesis and Characterization of an Ethylenediamine-Templated Mixed-Valence Titanium Phosphate

The mixed-valence compound TiIIITiIV(HPO4)4·C2N2H9·H2O (1) is synthesized hydrothermally from titanium powder, phosphoric and boric acids, and ethylenediamine. The compound is structurally stable up to 650 °C. It loses the template and the water molecule above 250 °C, all titanium becomes TiIV at 600 °C, and the result is the new compound TiIVTiIV(HPO4)4 (2). The structures of the two compounds were determined ab initio from powder diffraction data. Crystal data: TiIIITiIV(HPO4)4·C2N2H9·H2O, I41, a = 6.371(2), c = 16.571(1) A, V = 672.5(1) A3, Z = 2; TiIVTiIV(HPO4)4, I41/a, a = 6.335(2), c = 16.389(1) A, V = 657.7(1) A3, Z = 2. Both structures are of the open type, and the frameworks are nearly identical. Compound 2, τ-Ti(HPO4)2, is the first three-dimensional titanium hydrogen phosphate. Results of magnetization, TGA, BET, X-ray thermodiffractometry, and density measurements are also presented.

Hybrid Open Frameworks. 8. Hydrothermal Synthesis, Crystal Structure, and Thermal Behavior of the First Three-Dimensional Titanium(IV) Diphosphonate with an Open Structure: Ti3O2(H2O)2(O3P−(CH2)−PO3)2·(H2O)2, or MIL-22

Ti3O2(H2O)2(O3P−(CH2)−PO3)2·(H2O)2, or MIL-22, was prepared in a pure form under hydrothermal conditions (4 days, 493 K, autogenous pressure). Its structure was determined from single-crystal X-ray diffraction data. This compound is monoclinic (space group P21/c (no. 14)), with a = 6.3845(2) A, b = 11.1816(4) A, c = 11.7003(5) A, β = 99.994(1)°, V = 822.60(5) A3, and Z = 2. Its three-dimensional structure is built up from corner-shared trimeric units of titanium(IV) octahedra linked together via diphosphonate groups. This delimits a three-dimensional network with cross-linked 10-, 7-, and 6-membered ring tunnels along a, b, and c, respectively, at the intersection of which free water molecules are interacting with the terminal water bound to the titanium atoms. The thermal behavior, deduced from TGA and X-ray thermodiffractometry, is described.

Tl2Nb2O6+x (0 ≤ x ≤ 1): A Continuous Cubic Pyrochlore Type Solid Solution

Thallium metaniobate, Tl2Nb2O6, belongs to the cubic pyrochlore structural type (space group Fd3m). It is demonstrated by TGA, chemical analysis, and X-ray thermodiffractometry that it gives a continuous solid solution Tl2Nb2O6+x (0 ≤ x ≤ 1) under oxidation; the cubic pyrochlore structure is maintained with a continuous decreasing unit cell edge: x oxide ions being progressively incorporated into the network while x Tl3+ ions substitute to x Tl+ ones. Rietveld refinements of X-ray powder diffraction data reveal that, in the classical model of the pyrochlore structure, Tl+ and Tl3+ are disordered on half of the 32e positions for 0 ≤ x < 0.5 and on the 16d ones for 0.5 < x ≤ 1. Bond valence calculations are in good agreement with the decrease in the splitting of Tl cations from 32e to 16d positions when x increases, provided that a correlation exists between oxygen insertion and the Tl3+ distribution: each extra oxygen O' oxidizes one of its closest Tl neighbors to +3 while the three remaining monovalent Tl cations are repelled.

Preparation of europium doped barium bromofluoride thin films by physical vapour deposition

A new vapour phase deposition method of preparation of BaFBr:Eu 2+ phosphor films for digital X-ray imaging computed radiography has been developed. The thin films were obtained by coevaporation of EuF 2 and of the mixture BaFBr+10%(mole) BaF 2. The doping concentration and the film thickness can be respectively controlled by the temperatures of the vessels and the deposition times. The dehydration of BaBr 2.2H 2O and the synthesis of BaFBr were studied by X-ray thermodiffractometry. No oxihalide formation was detected in these experiments.

Oxyfluorinated Microporous Compounds: V. Synthesis and X-Ray Structural Determination of ULM-3, a New Fluorinated Gallophosphate Ga3P3O12F2, H3N(CH2)3NH3, H2O

Ga3P3O12F2, H3N(CH2)3NH3, H2O was obtained by hydrothermal synthesis (453 K, 24 hr, autogeneous pressure) from a mixture of Ga2O3, P2O5, HF, 1,3-diaminopropane, and H2O in the ratio 1:1:2:1.3:80. It is orthorhombic (space group Pbca (No. 61) with a = 10.154(1)Å, b = 18.393(2)Å, c = 15.773(2) Å, V = 2945.8(9) Å, Z = 8. The three-dimensional network is built up from corner-linked [Ga3(PO4)3F2] units composed of three PO4 tetrahedra, two GaO4F trigonal bipyramids, and one GaO4F2 octahedron. Fluorine atoms are shared between the octahedron and the bipyramid. The framework delimits 10-membered ring channels along [100] and 8-membered ones along [101] and [10-1]. The amine and the water molecule are inserted in the 10-membered ring channels. The hydrogen bonding scheme is discussed and shows that the water is principally linked to the amine within the tunnel and that the template might be the amine monohydrate. The thermal behavior of the title compound is studied by TGA and X-ray thermodiffractometry.

Synthesis, X-ray single crystal structure determination, and dehydration study of BaZr 2F 10 · 2H 2O by X-ray powder thermodiffractometry

Single crystals of BaZr 2F 10 · 2H 2O were prepared from BaF 2ZrF 4 mixtures in aqueous HCl solution. The crystal structure has been solved in the orthorhombic Pnam space group: a = 7.8974(3)Å, b = 7.9076(3)Å, c = 14.7227(4)Å, R F = 0.017, and R I = 0.023 from a twinned crystal whose apparent space group was P4 22 12. The bidimensional structure is built up from infinite corner-sharing in the (001) plane of [Zr 2F 14] 6− bipolyhedra formed by edge-sharing of two [ZrF 8] 4− trigonal dodecahedra; between each [Zr 2F 10] 2− layer, Ba atoms and H 2O molecules ensure the cohesion of the structure. The dehydration process has been studied by TGA and X-ray thermodiffractometry; at 130°C the first H 2O molecule reversibly leaves without damaging the crystal structure which becomes isotypic to that of TlZrF 5; above 150°C the second H 2O molecule continuously leaves up to 210°C, where the crystal structure collapses.