Crystal Growth in Magnetic Fields (II) Crystallization of Co(NH4)2(SO4)2 · 6 H2O from Aqueous Solutions in High Magnetic Fields

The displacement rate of (110) single crystal faces of Co(NH₄)₂(SO₄)₂ · 6 H₂O has been measured in dependence on the supersaturation of aqueous solutions in the zero field and at magnetic flux densities of 7 T. The results show that in a given external field measurable effects near the equilibrium don't occur (thermostatic field effect). On the contrary a marked influence at extreme relative supersaturations can be observed (kinetic field effect).     

Preparation and studies of new crystals in the K3H(SO4)2-(NH4)3H(SO4)2-H2O system

To elucidate the effect of isomorphic substitution on the kinetics of phase transitions, single crystals of (K _x (NH₄)_1?x ) _m H _n (SO₄)_{(m + n)/2} · yH₂O solid solutions are grown from the K₃H(SO₄)₂-(NH₄)₃H(SO₄)₂-H₂O system, whose end members are known to undergo superprotonic phase transitions of fundamentally different kinetics. The chemical composition of the single crystals grown is determined by energy dispersive X-ray microanalysis. The thermal and optical behavior of (K,NH₄)₉H₇(SO₄)₈ · H₂O single crystals is studied in the temperature range 295–420 K and the crystal structure at 295 K is determined. A comparison of the results of the studies with data for crystal K₉H₇(SO₄)₈ · H₂O published earlier shows that the substitution of ammonium for potassium atoms lowers the temperature of the structural phase transition by 8 K.     

Formation of solution inclusions in bicrystals of potassium-cobalt/potassium-nickel and ammonium-cobalt/ammonium-nickel sulfates

The crystallization of epitaxial layers from aqueous solutions in the K₂Co(SO₄)₂ · 6H₂O-K₂Ni(SO₄)₂· 6H₂O and (NH₄)₂Co(SO₄)₂· 6H₂O-(NH₄)₂Ni(SO₄)₂ · 6H₂O systems has been studied. A mechanism is proposed to explain the experimentally observed phenomena, taking into account the effect that elastic stresses have on the crystallization kinetics.     

The Characteristics of the Mixed Crystals of the K2SO4-(NH4)2SO4-H2O System at 298 K

Equilibrium studies of the K₂SO₄-(NH₄)₂SO₄-H₂O system at 298 K have been conducted. The isotherm of solubility and the curve of distribution have been mathematically described. The parameters of the crystal lattice and the enthalpy of crystallization of the [K_x(NH₄)_1-x]₂SO₄ solid solutions as a function of their composition have been presented.     

Crystal structure of octapotassium octasulfatodiceriate pentahydrate

Single crystals without Co and Ni have been crystallized by the substitution method in the K₂Ni(SO₄)₂-Ce(SO₄)₂-H₂SO₄-H₂O system using K₂Co(SO₄)₂ · 6H₂O, K₂ (Co,Ni)(SO₄)₂ · 6H₂O, or K₂Ni(SO₄)₂ · 6H₂O as protocrystals. The structure of the single crystals obtained has been established by X-ray diffraction analysis. The crystal structure contains dimer complex anions [Ce₂(μ-SO₄)₂(SO₄)₆]⁸⁻, K⁺ cations, and crystallization water molecules.     

Cs2Ni(SO4)2 · 6H2O (CNSH) crystal: Growth and some properties

Large single crystals of cesium-nickel sulfate hexahydrate Cs₂Ni(SO₄)₂ · 6H₂O of optical quality were grown for the first time. The crystal structure and the optical and thermogravimetric properties of this compound were investigated.     

Crystal growth,structure, crystalline perfection and characterization of zinc magnesium ammonium sulfate hexahydrate mixed crystals ZnxMg(1−x)(NH4)2(SO4)2·6H2O

Mixed crystals Zn_xMg_(1?x)(NH₄)₂(SO₄)₂·6H₂O of the two well-known Tutton's salts Zn(NH₄)₂(SO₄)₂·6H₂O and Mg(NH₄)₂(SO₄)₂·6H₂O were grown with varying molar proportions (x=0.10–0.90) by slow evaporation solution growth technique. The mixed crystal Zn_0.54Mg_0.46(NH₄)₂(SO₄)₂·6H₂O is crystallizing in monoclinic system with space group P2₁/c and cell parameters a=6.2217(4) Å, b=12.5343(7) Å, c=9.2557(6) Å, β=106.912(3)°. The coexistence of zinc and magnesium ions in the mixed crystal was confirmed by inductively coupled plasma (ICP), atomic absorption spectroscopy (AAS) and energy dispersive X-ray spectroscopy (EDS). Compositional dependence of lattice parameters follows Vegard's relations. Slight variations are observed in FT-IR and XRD of pure and mixed crystals. Comparison of crystalline perfection as evaluated by high-resolution X-ray diffraction (HRXRD) for mixed crystals of various proportions reveals a reasonably good crystalline perfection for the mixed crystal with nearly equimolar ratio of Zn and Mg. The surface morphology of the mixed crystals changing with composition was studied by scanning electron microscopy (SEM). UV–vis studies reveal that the transparency of the mixed crystals was not much affected.     

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.     

Superconducting Transition of (TMTSF)2CLO4 in Magnetic Fields

Abstract

Superconducting transition of (TMTSF)₂ClO₄ was studied by conductivity measurements along the most conductive a-axis in magnetic fields applied along three different principal crystallographic axes. The GL coherence lengths at OK along the a-, b-, and c*-axes, ?_a(0)≈ 600A, ?(0) ≈ 540A, and ?_c*(0) ≈ 60A were obtained from the measurements of the temperature dependence of the upper critical field H_C2 near the transition temperature. The anisotropy is discussed in terms of the dimensionality arising from the crystal structure and of the conductivity anisotropy in the normal state.     

Crystalloluminescence and Mechanoluminescence Spectra of Ba(ClO3)2 · H2O and 2 K2SO4 · Na2SO4 Crystals

Crystalloluminescence and mechanoluminescence of Ba(ClO₃)₂ · H₂O and 2 K₂SO₄ · Na₂SO₄ crystals are investigated. The crystalloluminescence spectra are almost similar to the photoluminescence spectra; however, they differ completely from the mechanoluminescence spectra. The crystalloluminescence excitations may take place due to the various processes: (i) the recombination of ions, (ii) from amorphous to crystalline transition, (iii) from the phase change during the crystallization, and (iv) from the dielectric breakdown by the electric field produced due to the creation of microfracture during the crystal growth. It is concluded that the crystalloluminescence excitation in Ba(ClO₃)₂ · H₂O and 2K₂SO₄ · Na₂SO₄ crystals may be chemical in origin.     

Mosaic microinhomogeneity in crystals of (Co,Ni)K2(SO4)2 · 6H2O solid solutions

The mosaic microinhomogeneity in mixed crystals of the isomorphic series (Co,Ni)K₂(SO₄)₂ · 6H₂O has been studied. The growth processes have been observed in situ in optical and confocal microscopes and the distribution of composition components has been studied by the energy-dispersive method. The results make it possible to develop model concepts about the formation of composition microinhomogeneity in solid solutions.     

IR and X-Ray Powder Diffraction Studies on Ba2Me(HCOO)6. 4 H2O (Me = Co,Ni, Zn)

It has been established that the double salts Ba₂Me(HCOO)₆. 4 H₂O (Me = Co, Ni, Zn) are isostructural with Ba₂Cu(HCOO)₆. 4 H₂O (trinclinic space group P1 = C¹_i). The infrared spectra of the double salts and their deuterated analogues have been recorded and the internal modes of the formate groups and the water molecules are reported. The analysis of the infrared spectra indicates that some of the internal formate modes (v₃ and v₄) reflect the existence of three crystallographically independent formate ions. The comparatively large frequency separations between the asymmetric and symmetric C–O stretching modes is a criterion for the different C–O bond lengths within each formate groups. The number and the positions of the bands in the high frequency range (4000–2300 cm⁻¹) are evidence for the existence of two inequivalent water molecules. The apearance of four uncoupled O–D modes in the spectra of the isotopically dilute samples shows that the water molecules are asymmetric. The librational modes of the water molecules are discussed as well.     

Synthesis and physicochemical characterization of a porous coordination polymer of Sn-Cu xylarate: The structure of [Sn4Cu8.5(HL)2(L)4O2(OH)(H2O)12.5] · 17.2H2O

A porous coordination polymer of Sn-Cu xylarate [Sn₄Cu_8.5(HL)₂(L)₄O₂(OH)(H₂O)_12.5] · 17.2H₂O (H₅ L is xylaric acid) is synthesized for the first time and characterized by chemical analysis, IR spectroscopy, and X-ray diffraction. Centrosymmetric heterometallic fragments [Sn₄Cu₆(HL)₂(L)₄O₂(H₂O)₆] (A) including copper Cu1–3 and tin Sn1,2 atoms are distinguished in the structure. The Cu4(OH)_0.5(H₂O)_2.5 bridges connect A units into chains running along the c axis, and the Cu5(OH)(H₂O) bridges connect A fragments into layers perpendicular to the c axis. The Cu4,5 atoms form a framework whose voids accommodate the crystallization water molecules.     

Growth of R 2 Me(SO4)2 · 6H2O single crystals with due regard for solubility diagrams of the R 2SO4-MeSO4-H2O systems (R = K, NH4; Me = Ni, Co)

The optimum conditions for growing R ₂ Me(SO₄)₂ · 6H₂O crystals are found from the analysis of the _{R 2} ⁺ SO₄-Me ²⁺SO₄-H₂O systems (R = K, NH₄; Me = Ni, Co) in the temperature range from 55 to 25°C. A new economical technology for growth of single crystals of double sulfate hexahydrates is developed, which allows the use of starting presynthesized solutions of hydrated or anhydrous K, Ni, Co, and (NH₄) sulfates. Transparent K₂Ni(SO₄)₂ · 6H₂O, K₂Co(SO₄)₂ · 6H₂O, and (NH₄)₂Ni(SO₄)₂ · 6H₂O crystals (35–55) × (25–40) × 10 mm in size are grown on seeds by the method of slow cooling.     

Vickers microhardness of K<Subscript>2</Subscript>Co(SO<Subscript>4</Subscript>)<Subscript>2</Subscript> · 6H<Subscript>2</Subscript>O single crystals and fracture geometry around impressions of vickers,knoop, and spherical indenters

The microhardness on the (010) and (001) planes in K₂Co(SO₄)₂ · 6H₂O crystal has been measured by the Vickers indentation method. Its values are, respectively, 11500 and 1300 MPa. No microhardness anisotropy of the first kind is revealed on either plane. The fracture geometry under indentation by a spherical indenter and Vickers and Knoop indenters is studied. The crystal has lower brittleness than the isomorphic Cs₂Ni(SO₄)₂ · 6H₂O crystal.     

Growth of Er2(SO4)3 ⋅ 8H2O crystals and study of their structure and properties

New crystals of the composition Er₂(SO₄)₃ ? 8H₂O have been synthesized by the method similar to that used for synthesis of (CH₃)₂NH₂Al(SO₄)₂ ? 6H₂O. The synthesized crystals were studied by the X-ray diffraction method. The crystals are monoclinic C2/c) and contain no (CH₃)₂NH₂ ions. It is established that, contrary to DMAAS crystals, Er₂(SO₄)₃ ? 8H₂O crystals undergo no phase transitions and possess neither ferroelectric nor ferroelastic properties.     

Electronic Structure of [Cu(C7H4NO3S)2(H2O)4] · 2H2O Crystal

The electronic absorption spectrum and ESR spectrum of the crystal of the title compound [Cu(C₇H₄NO₃S)₂(H₂O)₄] · 2 H₂O, are measured. The experimental results are discussed quantitatively by using the ligand field theory and the radial wave function of non-free Cu(II). The electronic structure of the compound is in agreement with its crystal structure.     

Structural features of a new [Fe(nicotinamide)2(H2O)4]·[Fe(H2O)6]·(SO4)2·2H2O complex

A new nicotinamide complex of Fe(II) cation was prepared by reaction between ferrous sulfate and nicotinamide in aqueous solution. The complex was characterized on the basis of elemental analysis, FT IR and UV–VIS spectroscopy, electrochemistry (cyclic voltammetry) and X–ray crystallography. The complex consists of the molecular composition of [Fe(nicotinamide)₂(H₂O)₄]· [Fe(H₂O)₆]·(SO₄)₂·2H₂O. The complex crystallizes in the monoclinic space group P 2₁/c [a = 12.862(3), b = 7.110(3), c = 16.382(3) Å; β = 95.79(2)°]. It has been proven that nicotinamide is coordinated to Fe(II) through the nitrogen atom of its heterocyclic ring. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Studies on the preparation and characterization of the Ce2(SO4)3 · 8(H,D)2O

Cerium Sulfate octohydrate crystals were crystallized from aqueous solutions under controlled conditions. The solubility measurements were carried out on temperatures between 10 and 80°. Thermoanalytical methods were applied for the study of the thermal behaviour of this compound. Raman spectra of polycrystalline Ce₂(SO₄)₃ · 8H₂O and Ce₂(SO₄)₃ · 8D₂O recorded at 80 K are reported. The vibrational modes have been assigned by comparing the spectrum of both compounds and using structural considerations.     

Synthesis and characterization of Ce2(SO4)3 · 5(H,D)2 O

The synthesis of cerium sulphate pentahydrate and its structure investigated by X-ray diffraction methods are reported. Analysis of the precession and Weissenberg photographs show that the crystals are twinned perfectly, in the sense that they are made of two single crystals with the true space group Cc. The dehydration of this compound has been studied using thermogravimetry and differential scanning calorimetric analysis in the temperature range 360 to 650 K. Powder Raman spectra of Ce₂(SO₄)₃ · 5 H₂O and Ce₂(SO₄)₃ · 5 D₂O have been measured at room temperature and the spectral assignments have been carried out by comparing these spectra with each other. Evidence of intermolecular hydrogen bonding has been found.