Growth and Physical Characterization of Double Cation Hydrogen Double Sulphate System Li2NaH(SO4)2 · H2O

Single crystals of Li₂NaH(SO₄)₂ H₂O are grown from aqueous solution, containing equimolar amounts of Li₂SO₄ H₂O and NaHSO₄ from 80°C down to 30°C over a period of 15 days, resulting in large good quality crystals. The as-grown crystals are verified by using XRD powder technique. The local structure is discussed in the light of vibrational spectroscopy. Water of crystallization is evidenced from both IR and Raman spectra. Several endothermic and an exothermic phase transition anomalies have been observed from DTA scan. Considerable weight loss is observed at 108°C from thermogravimetric study (TGA). The melting point of the material is found to be 450 °C. The density of the compound is measured to be 2.5217 g/cm³.     

Growth,Morphology, Structure and Properties of Na3BaCl5 2H2O Crystals

Single crystals of Na₃BaCl₅ 2H₂O were obtained from saturated aqueous solutions at two different temperatures (27° C and 32° C). The crystal size increases with increasing temperature. The crystals obtained were subjected to a systematic morphological, X-ray and thermal analyses. The study of as-grown crystal morphology and surface morphology of Na₃BaCl₅ 2H₂O crystals clearly indicate the requirement of a slow rate of evaporation at temperatures 27 to 28° C, moderate supersaturation in order to obtain high quality single crystals of Na₃BaCl₅ 2H₂O. The X-ray diffraction studies give the following cell parameters for the title compound: monoclinic, P21/n, a = 8.5773(9), b = 9.5502(4), c = 5.2873(3) A, β =92.069°, V = 432.8 A³, Z = 2. The study of TGA curves indicate the occurrence of dehydration process at around 200° C and not the decomposition of the compound. Similarly, the low temperature DSC study indicates a thermal anomaly at 267 K, and the high temperature DSC study (323 K to 873 K) indicates the transition from dihydrate to monohydrate and in turn anhydrous state at 454.6 K for Na₃BaCl₅ 2H₂O crystals. Thus both the TGA and DSC curves conclude that the Na₃BaCl₅ 2H₂O crystals contain two molecules of water of crystallization and its molecular formula is Na₃BaCl₅ 2H₂O.     

X‐Ray Powder Diffraction,DTA and Vibrational Studies of CdNH4PO4.6H2O Crystals

Cadmium Ammonium Phosphate Hexahydrate (CAPH) is analogous to naturally occurring struvite. CAPH crystals are grown by slow evaporation technique. These crystals are characterised by X‐ray, TG‐DTA and Infra‐red studies. Powder X‐ray pattern indicates the orthorhombic crystal structure analogous to struvite. TG‐DTA analysis suggests loss of water of hydration (6H₂O) between 113 and 391°C. Later the substance melts and only Cd remains around 780 °C. Infra Red spectrum is characteristic of H₂O, PO₄^3‐ and NH₄⁺ radicals.     

Synthesis,growth and characterization of a new nonlinear optical crystal: l‐arginine maleate dihydrate

A new nonlinear optical material L‐arginine maleate dihydrate, C₆H₁₄N₄O₂,C₄H₄O₄,2H₂O (LAMD) was synthesized and single crystals were grown by slow cooling and also by slow evaporation method at constant temperature from its aqueous solution. Quality and size of the crystals are found to be dependent on pH of the solution and best crystals were obtained at pH = 4. Single crystal X‐ray diffraction analysis reveal that the crystal lattice of LAMD is triclinic with unit cell parameters a = 5.264(3)Å, b = 8.039(3)Å, c = 9.784(3)Å, α = 106.19(3)°, β = 97.24(3)°, γ = 101.66(2)°. Second harmonic generation efficiency is found to be about 6.8 times that of quartz. It is optically transparent down to 300 nm and possesses a large optical window between 300–2000 nm. The compound is thermally stable up to 93.4 °C. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Corrosion and crystallization at the inner surfaces of glass bricks

Glass bricks are important transparent building materials. They are produced by joining two halves of glass pressings at 600–700 °C. During this production process alkali oxides evaporate and are redeposited at the cooler inner front surfaces of the bricks. This surface layer reacts with H₂O and CO₂ from the residual brick atmosphere, leading to the formation of an alkali-rich silicate-hydrate layer of ?50 nm thickness, which could be evidenced leading to a reduced nano-hardness of similar thickness, and from which NaHCO₃ crystals can finally grow. Climate chamber experiments (repeated cooling between at ?8 and ?14 °C and reheating to 0 to 15 °C) resulted in reversible NaHCO₃ crystallization and redissolution, presumably influenced by water evaporation or condensation and driven by the NaHCO₃ supersaturation of the silicate-hydrate layer. Depending on the time–temperature schedule, different crystal morphologies became visible in this closed system, e.g. isolated spherical crystals, crystals arranged in chains and in double-chains, respectively, which can limit already the transmittance of the glass bricks. When a crack occurs or the brick is opened, the hygroscopic NaHCO₃ crystals take up more H₂O from the ambient, react irreversibly with the glass surface, finally leading to a total loss of transmittance.     

Precipitation of nesquehonite from homogeneous supersaturated solutions

The homogeneous (unseeded) precipitation of nesquehonite (MgCO₃·3H₂O) was studied over the temperature range of 10‐40 °C. Precipitation was triggered by the supersaturation created by mixing MgCl₂ solution (0.5‐1.5 M) with Na₂CO₃ solution in the same concentration range. The Meissner's method was adopted in the calculation of supersaturations during the MgCl₂‐Na₂CO₃ reaction to monitor the precipitation. Solids were identified using X‐ray diffraction (XRD) analysis and scanning electron microscope (SEM) images. In the temperature range of 10‐40 °C, MgCO₃·3H₂O with needle‐like or gel‐like morphology was precipitated. It was seen that the length, width and surface smoothness of the particles changed with reaction temperature and supersaturation. The supersaturation (S) was in the range of 1.09‐58.68 during titration of Na₂CO₃ solution. The dimension of the crystals increased with longer addition time (or lower initial concentration of reactant) at the same temperature. Slower addition via titration of 2 h followed by 2 h of equilibration at 40 °C proved successful in producing well developed needle‐like MgCO₃·3H₂O crystals of 30‐50 μm long and 3‐6 μm wide. MgCO₃·3H₂O obtained were calcined to produce highly pure magnesium oxide (MgO) at 800 °C. The morphology of MgO was similar to that of their corresponding precursors. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hydrothermal Synthesis of Zeolite Crystals Using Natural Scolecite

Natural scolecite is converted into analcime type zeolite by hydrothemal method at 180 °C at autogeneous pressure for 24 to 160 hours growth runs. Mordenite is detected in the final product. Cube and spheroid crystals of the products are illustrated and described. Crystals synthesized are characterized by X-ray diffraction, infrared spectroscopy EDAX and scanning electron microscopy. Particle size is estimated as 20–60 microns, induction period for nucleation as 12 hrs, and lattice parameter of cube crystals as 13.70 Å. Mechanism of growth, influence of anions and duration of growth etc. are discussed. It is established that the crystals grow in the system Na₂O Al₂O₃ SiO₂ H₂O.     

Synthesis and characterization of ZSM-8-type zeolite crystals

Procedure for hydrothermal synthesis of ZSM-8-type zeolite crystals, using TEA—OH as a template, in the system having molar composition 16.2 (Na₂O) — Al₂O₃ — 117 (SiO₂) — 4.8 (TEA)₂O — 3887 H₂O at 170 °C is described. Results of characterization of these crystals by XRD, IR, EDAX, SEM, TGA, and adsorption studies are described and discussed. X-ray diffraction studies establish that the crystals are ZSM-8-type with structure similar to that of ZSM-5-type crystals. Crystals have prismatic bipyramidal morphology with average size 18–25 microns. Degased calcined samples adsorb xylenes in the order p > m > 0. Pore length per unit cell, estimated from n-hexane adsorption studies, is 46 Å.     

Kristallstrukturänderungen des Magnesiumnitrats-Hexahydrats,die infolge isodimorpher Substitution durch Co(II)- und Ni(II)-Ionen entstehen

The physico-chemical analysis data on the systems Mg(NO₃)₂ Co(NO₃)₂ H₂O and Mg(NO₃)₂ Ni(NO₃)₂ H₂O at 25.0°C have shown that due to isodimorphous substitution of Mg²⁺ in the crystals of Mg(NO₃)₂ · 6 H₂O for Co²⁺ or Ni²⁺, above a specific degree of ionic substitution, changes in the crystal structure of Mg(NO₃)₂ · 6 H₂O appear.     

Growth of single crystals of NaH2PO4 (NaDP), NaH2PO4 · H2O (NaDP · H2O), and NaH2PO4 · 2H2O (NaDP · 2H2O) sodium dihydrogenphosphate based on the analysis of the Na2O-P2O5-H2O phase diagram

The crystallization conditions for the NaH₂PO₄, NaH₂PO₄ · H₂O, and NaH₂PO₄ · 2H₂O solid phases have been established from the analysis of the phase diagram of solubility of the ternary Na₂O-P₂O₅-H₂O system in the temperature range from 0 to 100°C. Based on these data, the methods for growing sodium dihydrogenphosphate single crystals of the above compositions are developed. The initial components for preparing mother solutions were H₃PO₄ and NaOH solutions taken in certain weight ratios. For the first time, NaDP, NaDP · H₂O, and NaDP · 2H₂O single crystals were grown on a seed by the method of temperature decrease. The habits of the NaDP and NaDP · H₂O single crystals are determined. __________ Translated from Kristallografiya, Vol. 47, No. 5, 2002, pp. 937–944. Original Russian Text Copyright ? 2002 by Soboleva, Voloshin.     

Growth of CuSO4 · 5H2O single crystals and study of some of their properties

Large single crystals of copper sulfate pentahydrate CuSO₄ · 5H₂O of optical quality have been grown; they can be applied as broadband UV optical filters. Their transmission spectra are measured. The crystal thermal stability is investigated and the onset temperature of dehydration is determined to be 46°C.     

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.     

Structural defects and their genesis in corundum monocrystals

Besides the formation of dislocations and block boundaries behind the crystallization front, there is much experimental evidence indicating the presence of rather big aggregates in various crystal-forming media. Experimental facts are given proving them to exist in Al₂O₃ melt. The perfection of a grown crystal depends on aggregation degree of the melt which can be controlled by both impurity cncentration and supercooling of the melt. E.g. in Verneuil-grown crystals a change in Cr concentration from 1 ṁ 10⁼³ to 1% leads to a change in aggregate sizes from 100 to 1000 Å. With Stepanov-, Czochralski-, and horizontally directed crystallization methods a variation in supercooling the melt enables to change the size of the aggregates from 150 to 400 Å. High values of the diffusion coefficient are accounted for by a higher concentration of the holes. The main reason increasing the number of holes in the crystals grown by the mentioned methods is the presence of the boundaries between incoherently accreted aggregates.     

Crystallization studies by thermometric methods (II). Calorimetric determination of chrystallization kinetics of sodium sulfate and sodium carbonate decahydrates

A calorimetric method was applied for the determination of crystallization kinetics of vibrationally mixed suspensions of Na₂SO₄ · 10 H₂O and Na₂CO₃ · 10 H₂O at 25°C with supersaturations up to 0.083 and 0.119 g hydrate/g free water, resp. The characteristic dimension of crystals was 0.125–0.63 mm.     

Crystal growth of mixed‐valence ammonium vanadates

A new method has been developed for the synthesis of mixed‐valence ammonium vanadate crystals. Single crystals of (NH₄)₂V₃O₈ were synthesized on a large scale by hydrothermal reduction of NH₄VO₃ in ethanol‐H₂O solutions in the presence of triblock copolymer Pluronic P123. The crystals are shining thin plates with (001) cleavage planes. Calcination of the (NH₄)₂V₃O₈ crystals at 300°C or above resulted in pure phases of V₂O₅. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of dopants and preparation method on the thermoluminescence properties of corundum crystals

Thermoluminescence (TL) of several types of corundum crystals is described. Undoped crystals showed a weak TL at 15 and 110°C with emission at 330 and 495 nm. Good TL response at 275°C is shown by Cr doped (0.03 wt%) crystals grown by Verneuil method in the oxygen cone of the flame annealed in hydrogen at 1500–1800°C. The most intensive TL response is shown by crystals doped with Ti and Mo (∼ 10⁻³wt.%) grown by Czochralski method in reducing conditions. The former may be used to the detection of γ-rays dose ≥ 10⁻³ − 10⁻² Gy, the latter ≥ 10⁻⁷ − 10⁻⁶ Gy.     

Induced growth of Pb0.97La0.02(Zr0.66Sn0.27Ti0.07)O3 antiferroelectric single crystals with a platinum wire

Relaxor antiferroelectric (Pb,La)(Zr,Sn,Ti)O₃ (PLZST) with the composition near the morphotropic phase boundary shows excellent electrical properties. However, the crystal growth of PLZST is limited by the incongruent melting of the materials. Crystal growth of PLZST was induced by a platinum wire in the flux solution with 50 wt% PbO‐PbF₂‐B₂O₃ as a solvent. The obtained PLZST single crystals are optical transparent with light yellow color. The size of the crystals in regular rectangular shape varies from 0.5 mm to 1 mm. The PLZST single crystals exhibit tetragonal phase structure. The element contents of the crystals were measured by inductively coupled plasma atomic emission spectrometry. The results show that the composition of as‐grown crystals is a little bit deviated from the starting composition. The single crystals show two dielectric peaks at 115 °C and 182 °C, corresponding to antiferroelectric‐ferroelectric and ferroelectric‐paraelectric phase transitions. The dielectric data of as‐grown crystals indicate there is typical relaxor behavior near 182 °C. The value of relaxor factor n is 1.49642.     

Synthesis,characterization, and crystal structure of 5,5″-Difluoro-1<Emphasis Type="Italic">H</Emphasis>,1″<Emphasis Type="Italic">H</Emphasis>-[3,3′:3′,3″-terindol]-2′(1′<Emphasis Type="Italic">H</Emphasis>)-one

The new indole derivative, 5,5′′-Difluoro-1H,1′′H-[3,3′:3′,3′′-terindol]-2′(1′H)-one C₂₄H₁₅F₂N₃O, is synthesized in 87% yield, and its crystal structure is determined by X-ray structure analysis. The crystals are monoclinic, sp. gr. P2₁/n, a = 15.4563(7), b = 10.8340(6), c = 16.4718(6) Å, β = 102.403(4)°, Z = 4. Bicyclic indole moieties form dihedral angle of 61.92(5)° with each other; the oxindole ring is twisted with respect to them at angles of 85.70(5)° and 75.62(5)°. The crystal structure is stabilized by N–H···O and C–H···O hydrogen bonds involving both the DMSO solvent molecules. In addition, one C–H···π interaction is observed.     

Study of the Growth Morphology of Ammonium Oxalate Monohydrate Crystals Obtained from Aqueous Solutions

The experimental results of the growth morphology of ammonium oxalate monohydrate [(NH₄)₂C₂O₄ · H₂O; AO] single crystals obtained from aqueous solutions at 30 and 40 °C and supersaturation up to 9% are presented. The observations are compared with the theoretical morphology predicted by PBC analysis and Braivais-Donnay-Harker law.     

Change in the crystal structure of zink(II) sulphate heptahydrate and magnesium(II) sulphate heptahydrate due to isodimorphous substitution by copper(II), iron(II), and cobalt(II) ions

The physico-chemical analytical data on the systems ZnSO₄(MgSO₄)–CuSO₄(FeSO₄, CoSO₄ resp.)–H₂O at 25.0°C have shown that due to isodimorphous substitution of Zn²⁺, Mg²⁺ resp., in the orthorhombic crystals of ZnSO₄ · 7 H₂O MgSO₄ · 7 H₂O, resp. for Cu²⁺, Fe²⁺ or Co²⁺ above a specific degree of ionic substitution, the orthorhombic crystals are converted into monoclinic mixed crystals. The crystal phases are characterized by X-ray diffraction, microscopic and optical studies. The dominant effect of the admixed Cu²⁺, Fe²⁺, Co²⁺ ions is explained in terms of their electronic configurations, for which, owing to the operation of the Jahn-Teller effect, a deformation of the regular octahedral arrangement of the water ligands about the metal ion is found to occur. The strongest deforming effect is that of Cu²⁺ ions followed by the Fe²⁺ ions, the weakest deforming effect being that of Co²⁺ ions.