Growth and shape control of orthorhombic Fe5(PO4)4(OH)3·2H2O single crystalline dendrites

Orthorhombic Fe₅(PO₄)₄(OH)₃·2H₂O single crystalline dendritic nanostructures have been synthesized by a facile and reproducible hydrothermal method without the aid of any surfactants. The influences of synthetic parameters, such as reaction time, temperature, the amount of H₂O₂ solution, pH values, and types of iron precursors, on the crystal structures and morphologies of the resulting products have been investigated. The formation process of Fe₅(PO₄)₄(OH)₃·2H₂O dendritic nanostructures is time dependent: amorphous FePO₄·nH₂O nanoparticles are formed firstly, and then Fe₅(PO₄)₄(OH)₃·2H₂O dendrites are assembled via a crystallization-orientation attachment process, accompanying a color change from yellow to green. The shapes and sizes of Fe₅(PO₄)₄(OH)₃·2H₂O products can be controlled by adjusting the amount of H₂O₂ solution, pH values, and types of iron precursors in the reaction system.     

Crystal growth of ferroelastic K2Cd2(SO4)3 and the K2SO4-CdSO4 phase diagram

Crystals of congruently melting K₂Cd₂(SO₄)₃ (having the langbeinite structure with a ferroelastic transition temperature of 156°C) were grown by the Bridgman and Czochralski techniques. The former yielded colorless crystals when using oxygen under pressure; the latter yielded tan crystals of slightly smaller unit cell volume and are assumed to be oxygen deficient. The ferroelastic transition was studied by thermal expansion measurements. Reexamination of the phase diagram showed the existence of a previously unreported phase K₆Cd(SO₄)₄ which is stable only between 520°C and the melting point of about 890°C.     

Crystal structure of M4[(UO2)2C2O4(SO4)2(NCS)2] ( M = K+, Rh+) and K4[(UO2)2C2O4(SeO4)2(NCS)2]

Three heteroacidoligand uranyl complexes M ₄[(UO₂)₂C₂O₄(SO₄)₂(NCS)₂] (M = K⁺ (I), Rb⁺ (II)) and K₄[(UO₂)₂C₂O₄(SeO₄)₂(NCS)₂] (III) have been synthesized and their crystal structure has been determined by X-ray diffraction analysis. The compounds I–III are isostructural and crystallized in the monoclinic system, sp. gr. P2₁/c, Z = 2, a = 11.5548(3) ?, b = 7.0847(1) ?, c = 13.5172(3) ?, β = 93.130(1)°, V = 1104.90(4), R = 0.015 (I); a = 11.5854(9) ?, b = 7.3841(6) ?, c = 13.9072(9) ?, β = 95.754(3)°, V = 1183.74(15), R = 0.0235 (II); a = 11.6715(3) ?, b = 7.1418(2) ?, c = 13.8546(1) ?, β = 93.539(1)°, V = 1152.66(5), R = 0.0126 (III). Basic structural units of these crystals are [(UO₂)₂C₂O₄(XO₄)₂(NCS)₂]⁴⁻ chains, which belong to the crystallochemical group A ₂ K ⁰² B ₂² M ₂¹ (A = UO₂²⁺, K ⁰² = C₂O₂₋⁴, B ² = SO₄²⁻ or SeO₄²⁻, M ¹ = NCS⁻) of uranyl complexes. Uranium-containing chains are connected into a 3D framework via a system of electrostatic interactions with potassium or rubidium cations from outer spheres. Original Russian Text ? I.V. Medrish, E.V. Peresypkina, A.V. Virovets, L.B. Serezhkina, 2008, published in Kristallografiya, 2008, Vol. 53, No. 3, pp. 495–498.     

Crystal structure of PbUO2(CH3COO)4(H2O)3

Single crystals of PbUO₂(CH₃COO)₄(H₂O)₃ have been investigated by X-ray diffraction (R = 0.029 for 3175 reflections). The structure of this compound is formed by [Pb(CH₃COO)(H₂O)₃]⁺ chains, which are oriented along the [100] axis and limited by one-core complexes [UO2(CH₃COO)₃]⁻. The coordination numbers of the Pb(II) and U(VI) atoms are 8, and the coordination polyhedron of uranium is a hexagonal bipyramid whose vertices contain oxygen atoms of three bidentate cyclic acetate groups and the uranyl group. Taking into account the different crystallographic roles of acetate ions, the crystal-chemical formula of [PbUO₂(CH₃COO)₄(H₂O)₃] chains can be written as AA′B ²¹ B ¹¹(B ⁰¹)₂ M ₃¹, where A = Pb; A′ = UO₂²⁺; M ¹ = H₂O; and B ²¹, B ¹¹, and B ⁰¹ are CH₃COO⁻ groups.     

Synthesis and crystal structure of (NH4)3[UO2(CH3COO)3]2[UO2(CH3COO)(NCS)2(H2O)]

Single crystals of the compound (NH₄)₃[UO₂(CH₃COO)₃]₂[UO₂(CH₃COO)(NCS)₂(H₂O)] (I) are synthesized, and their structure is investigated using X-ray diffraction. Compound I crystallizes in the monoclinic system with the unit cell parameters a = 18.3414(6) ?, b = 16.3858(7) ?, c = 12.4183(5) ?, β = 92.992(1)°, space group C2/c, Z = 4, V = 3727.1(3) ?³, and R = 0.0253. The uranium-containing structural units of crystals I are mononuclear complexes of two types with an island structure, i.e., the [UO₂(CH₃COO)₃]⁻ anionic complexes belonging to the crystal-chemical group (AB ₃⁰¹ = UO₂²⁺, B ⁰¹ = CH₃COO⁻) of the uranyl complexes and the [UO₂(CH₃COO)(NCS)₂(H₂O)]⁻ anionic complexes belonging to the crystal-chemical group AB ⁰¹M₃¹ (A = UO₂²⁺, B ⁰¹ = CH₃COO⁻, M ¹ = NCS⁻ or H₂O).     

Characteristic features of the change of domain structure in mixed [(NH4)1?xRbx]3H(SO4)2 crystals in the vicinity of superprotonic phase transition

X-ray diffraction measurements of mixed [(NH₄)_1−x Rb_x]₃H(SO₄)₂ crystals of different compositions are performed. The characteristics of the change of the domain structure in the vicinity of the supeprotonic-ferroelastic phase transition in crystals of different compositions are studied and compared with the variations of the crystal structure in the course of gradual substitution of ammonium by rubidium. This phase transition is theoretically described based on the phenomenological theory of a high-temperature phase transition. __________ Translated from Kristallografiya, Vol. 50, No. 1, 2005, pp. 115–121. Original Russian Text Copyright ? 2005 by Kirpichnikova, Polomska, Pietraszko, Shakhmatov, Hilczer.     

Crystal structure and phase transitions in the new crystals of [(CH3)2NH2]2CuCl4[(CH3)2NH2]Cl

Crystals grown from a solution of dimethylammonium and copper chlorides are studied using electron paramagnetic resonance (EPR) and X-ray diffraction. The dielectric properties of the crystals grown are measured. It is established that the crystals have the composition [(CH₃)₂NH₂]₂CuCl₄[(CH₃)₂NH₂]Cl and, in phase I at room temperature, are described by the orthorhombic space group Pna2₁ with the unit cell parameters a = 11.338 Å, b = 9.981 Å, and c = 15.675 Å. At temperatures of 279 K and 253 K, the crystals undergo jumpwise phase transitions into the incommensurate modulated ferroelectric phase II and commensurate modulated phase III, respectively. __________ Translated from Kristallografiya, Vol. 49, No. 1, 2004, pp. 92–100. Original Russian Text Copyright ? 2004 by Kirpichnikova, Pietraszko, Bednarski, Waplak, Sheleg. Dedicated to the 80th Birthday of L.A. Shuvalov     

Synthesis and crystal structure of rare earth selenates Nd(HSeO4)3, Sm(HSeO4)3, and Nd2(SeO4)3 · 5H2O

Single crystals of rare earth (RE) selenates of the compositions Nd(HSeO₄)₃, Sm(HSeO₄)₃, and Nd₂(SeO₄)₃ · 5H₂O are synthesized and studied by X-ray diffraction analysis at T = 297 and 180 K. It is established that Nd and Sm hydrogen selenates are isostructural to one another and to the corresponding hydrogen sulfates. Neodymium selenate pentahydrate is not isostructural to the analogous RE sulfates, although their structural motifs are similar. __________ Translated from Kristallografiya, Vol. 49, No. 5, 2004, pp. 835–840. Original Russian Text Copyright ? 2004 by Zakharov, Troyanov, Kemnitz.     

Effect of the number of defect density waves on the dynamics of the soliton system in [N(CH3)4]2CuCl4 and [N(CH3)4]2Zn0.98Ni0.02Cl4 crystals

The time dependences of the birefringence and thermal conductivity of [N(CH₃)₄]₂CuCl₄ and [N(CH₃)₄]₂Zn_0.98Ni_0.02Cl₄ crystals in the incommensurate phase at a constant temperature have been studied. A multiwave state of modulated superstructure is found to be formed in the presence of defect density waves in the crystal. It is shown that, depending on the number of defect density waves in the crystal, either a superposition of existing modulation waves or a domainlike structure arise in it.     

A novel representative {[Rb1.94(H2O,OH)3.84](H2O)0.1}{Al4(OH)4[PO4]3} in the pharmacosiderite structure type

The crystal structure of a new synthetic aluminophosphate {[Rb_1.94(H₂O,OH)_3.84](H₂O)_0.1}{Al₄(OH)₄[PO₄]₃} synthesized under mild hydrothermal conditions (T = 280°C, P = 100 atm) in the Rb₂O-Al₂O₃-P₂O₅-H₂O system is determined using X-ray diffraction (Stoe IPDS diffractometer, λMoK _α, graphite monochromator, 2θ_max = 64.33°, R = 0.032 for 312 reflections). The main crystal data are as follows: a = 7.4931(6) ?, space group P 3m, Z = 1, and ρ_calcd = 2.76 g/cm³. It is shown that the synthesized compound belongs to the pharmacosiderite structure type with a characteristic mixed open microporous framework composed of octahedra and tetrahedra. A comparative crystal chemical analysis of related phases is performed, and the chemical compositions of promising absorbents, i.e., hypothetical compounds potentially possible in the structure type under consideration, are proposed. It is established that pharmacosiderite and rhodizite are homeotypic to each other. Original Russian Text ? O.V. Yakubovich, W. Massa, O.V. Dimitrova, 2008, published in Kristallografiya, 2008, Vol. 53, No. 3, pp. 442–449.     

A new dabco templated metal sulfate, (C6H14N2)[Mn (H2O)6](SO4)2. Chemical preparation, hydrogen-bonded structure and thermal decomposition

The crystal structure of manganese sulfate templated by 1,4-diaza-bicyclo[2.2.2]octane (abbreviated dabco), (C₆H₁₄N₂)[Mn(H₂O)₆](SO₄)₂, was investigated using single crystal X-ray diffraction data. It crystallises in the monoclinic system (space group P2₁/c) with the following unit-cell parameters: a = 12.1392(2) ?, b = 12.3117(2) ?, c = 12.2765(2) ?, β = 104.607(1)°, V = 1775.47(5) ?³ and Z = 4. The structure has been solved using direct methods and refined by least-squares analysis [R ₁ = 0.0381, wR ₂ = 0.1082]. The crystal structure of the title compound is built from isolated [Mn(H₂O)₆]²⁺ octahedral cations, 1,4-diaza-bicyclo[2.2.2]octandiium cations (C₆H₁₄N₂)²⁺ and sulfate anions (SO₄)²⁻ connected by a three-dimensional hydrogen-bond network. The thermal decomposition of the precursor, studied by thermogravimetry and temperature-dependent X-ray powder diffraction, proceeds through four stages giving rise to the mixture of Mn₂O₃and Mn₃O₄. Supplementary Material CCDC 620298 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.     

Crystal structure of the UO2SO4 · 2SO(CH3)2 compound: A new type of uranyl sulfate ribbons and the UO2SO4 · 2SO (CH3)2-UO2SO4 · 2CO(NH2)2 morphotropic transition

Single crystals of bis(dimethyl sulfoxide) uranyl sulfate are prepared, and their crystal structure is determined using X-ray diffraction analysis. The crystals are monoclinic, space group P2₁/c, a = 12.9189(8) ?, b = 7.9008(5) ?, c = 12.1405(7) ?, β = 95.677(1)°, R ₁ = 0.0216, wR ₂ = 0.0468 for 2761 unique reflections with F > 2σ(F). The crystal structure of the UO₂SO₄ · 2Dmso compound (where Dmso is dimethyl sulfoxide) is built up of infinite uncharged ribbons of the composition [UO₂SO₄ · 2Dmso]_∞, in which the SO₄ tetrahedron is tridentately coordinated to two uranyl groups. The differences between the structures of the uranyl sulfate compounds formed upon replacement of dimethyl sulfoxide by other molecules are considered. Original Russian Text ? E.V. Alekseev, E.V. Suleĭmanov, E.V. Chuprunov, G.K. Fukin, E.V. Baranov, 2007, published in Kristallografiya, 2007, Vol. 52, No. 2, pp. 283–286.     

Structural Correlations in High-Spin Complexes of [Fe{HC(3,5-Me2pz)3}2]2+: Solid State Structure of [Fe{HC(3,5-Me2pz)3}2][Fe2OCl6]

Abstract  The cation in the solid state structure of [Fe{HC(3,5-Me₂pz)₃}₂][Fe₂OCl₆] (pz = pyrazolyl ring) contains an octahedral iron(II) center with an average Fe–N bond distance of 2.17 Å, indicating that the iron(II) is in the high-spin form. While M–N bond distances of this length with κ³-[HC(3,5-Me₂pz)₃] ligands generally cause tilting of pz to open up the “bite” angle, in this structure the average tilting angle is only 3.1°, a much lower value than observed in earlier structures of this same cation paired with different anions. The crystals are monoclinic, space group P2₁/n, with a = 11.1671(12) Å, b = 10.8091(11) Å, c = 17.4385(17) Å, α = γ = 90°, β = 95.685(2)°, and Z = 2. Graphical Abstract  The cation in the solid state structure of [Fe{HC(3,5-Me₂pz)₃}₂][Fe₂OCl₆] (pz = pyrazolyl ring) contains an octahedral iron(II) center in the high-spin form with unusual orientations of the pyrazolyl rings.      

Gel-glass transformation in the SiO2Fe2O3 system

Gel-glass transformation has been studied by Mössbauer spectroscopy, DTA-TG analyses and X-ray diffractometry for four compositions in the SiO₂Fe₂O₃ system (A: 5 wt% Fe₂O₃, B: 10 wt% Fe₂O₃, C: 20 wt% Fe₂O₃, D: 40 wt% Fe₂O₃).The gels were prepared by the hydrolysis of silicon tetraethoxide and iron triethoxide and successively dried and heated in oxygen in the temperature range 40–1000°C.Samples A and B gave typical amorphous X-ray patterns up to 700°C; heating at higher temperature yielded the precipitation of quartz, cristobalite and hematite in sample A, cristobalite and hematite in sample B. Crystallization was also detected by DTA in sample A for which X-ray diffraction exhibited a larger effect.In samples C and D crystallization took place starting from 300°C with the precipitation of hematite, which remained the only crystalline phase up to 1000°C.The presence of hematite was confirmed by the obtained Mössbauer spectra which showed the characteristic sextet. The apportion of iron ions in the Fe³⁺ and Fe²⁺ oxidation states was also determined, together with the attribution of the probable coordination states for Fe³⁺ ions.Complex magnetic structure appeared in samples treated above 800°C.     

Magnetic behaviour of 20Fe2O380[3B2O3(1−χ)PbOχAs2O3] glasses

The results of magnetic measurements performed on 20Fe₂O₃80[3B₂O₃(1?χ)PbOχAs₂O₃] glasses, in the temperature range 4.2 to 300 K are reported. By decreasing the temperature a downward curvature of reciprocal susceptibility is observed for T<50 K. The composition dependence of the paramagnetic Curie temperatures and Curie constants is discussed.     

Glass formation through hydrolysis of Si(OC2H5)4 with NH4OH and HCl solution

Monolithic silica glass was obtained by heating the gels prepared by hydrolyzing Si(OC₂H₅)₄ with NH₄OH and HCl solution. The effect of the condition of hydrolysis of Si(OC₂H₅)₄ on glass formation was examined by measuring the bulk density, the infrared spectra and the thermal shrinkage of the gel on heating. The gel prepared by hydrolysis with NH₄OH solution consisted of numerous spherical particles, the bulk density being about 0.8. This gel abruptly shrank at about 1050°C, being converted to the pore free material similar to fused silica. The conversion of the gel to glass followed the sintering model in which the viscous flow controlled the sintering process. The viscosity and the activation energy for viscous flow were calculated on the basis of the Frenkel equation. On the other hand, the spherical particles were not observed in the gel prepared by hydrolysis with HCl solution. The bulk density of the gel was about 1.8. This gel was converted to glass at about 700°C, which was lower than the temperature of glass formation for the gel obtained by hydrolysis with NH₄OH solution.     

Crystal growth of NdAl3(BO3)4 from K2O/MoO3/Nd2O3/B2O3/KF flux

NdAl₃(BO₃)₄ single crystals were grown by the flux method and the TSSG technique using a K₂O/3MoO₃/B₂O₃/0.5Nd₂O₃/KF flux system. Light-violet clear crystals could be obtained. The effects of fluoride on the growth of NAB crystals were investigated. As the content of KF was gradually increased, the growth form of NAB was changed from the equant to the columnar and the primary crystalline region of NAB was shrinked. At the ratio of KF/K₂O = 0.75, NAB crystals could not be grown.     

X-ray diffraction study of phase transitions in Na3Sc2(PO4)3 and Ag3Sc2(PO4)3 single crystals in temperature range from 160 to 500 K

Two phase transitions are revealed for the first time in Ag₃Sc₂(PO₄)₃ single crystals in the vicinity of the temperatures 303 and 165–180 K. It is established that the phase transition at 303 K corresponds to the well-known phase transition to the superionic state in Na₃Sc₂(PO₄)₃ single crystals in the temperature range 423–433 K, whereas the phase transition observed in the temperature range 170–180 K corresponds to the phase transition from the rhombohedral to monoclinic phase at about 320 K in the monoclinic Na₃Sc₂(PO₄)₃ single crystals. It is also established that rhombohedral Na₃Sc₂(PO₄)₃ single crystals undergo the second phase transition. __________ Translated from Kristallografiya, Vol. 50, No. 1, 2005, pp. 122–126. Original Russian Text Copyright ? 2005 by Shilov, Atovmyan, Kovalenko.     

Solubility phase diagrams of Me 2SO4-NiSO4-H2O systems and the growth of Me 2Ni(SO4)2 · n H2O crystals [ Me = Na, Rb, Cs; n = 4, 6]

On the basis of the physicochemical analysis of the solubility phase diagrams for the Me ₂SO₄-NiSO₄-H₂O ternary systems (Me = Na, Rb, or Cs), the optimum concentration and temperature conditions for the crystallization of the Me ₂Ni(SO₄)₂ · nH₂O solid phases were found. Techniques for growth of single crystals of these binary salts have been developed. Such techniques allow application of mother liquors containing hydrates or anhydrous sulfates of Na, Rb, Cs, and Ni as raw materials. Na₂Ni(SO₄)₂ · 4H₂O, Rb₂Ni(SO₄)₂ · 6H₂O, and Cs₂Ni(SO₄)₂ · 6H₂O single crystals (28–34) × (8–13) × (5–10) mm³ in size have been grown from aqueous solutions in the dynamic regime. Original Russian Text ? L.V. Soboleva, 2007, published in Kristallografiya, 2007, Vol. 52, No. 6, pp. 1141–1144.