Ca for Er substitution in tetragonal ErPO4 · H2O crystallised from phosphoric acid solution

Erbium phosphate monohydrate with limited Ca for Er substitution, obtained through crystallisation from boiling phosphoric acid solution has been characterised by X‐ray diffraction, Ir‐spectroscopy and thermal analysis (TGA‐DTA) methods. The difference in the electric charge between di‐valent calcium and tri‐valent erbium in the solid crystallised was compensated by simultaneous substitution of HPO₄^2‐ for PO₄^3‐. Ca incorporation in erbium phosphate made expansion of tetragonal ErPO₄ · H₂O unit cell. After ignition at 900 °C the tetragonal crystal modification was maintained but the unit cell parameters of all the investigated phosphates, whether Ca‐substituted or Ca‐free, contracted to the same level. The unique contraction of the unit cell was resulted from recrystallisation of Ca‐substituted into Ca‐free erbium phosphate, while Ca was transferred into Ca(PO₃)₂ formed as a separate phase. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Composition and morphology control of Fex(PO4)y(OH)z·nH2O microcrystals

A series of Fe_x(PO₄)_y(OH)_z·nH₂O microcrystals were prepared by the hydrothermal reaction at 150 °C. The ratio of Fe²⁺/Fe³⁺ in Fe_x(PO₄)_y(OH)_z·nH₂O microcrystals can be adjusted by using Na₂S₂O₃·5H₂O as a reducing agent. The morphology control of Fe_x(PO₄)_y(OH)_z·nH₂O microcrystals was realized through regulating the molar ratio of LiAc·2H₂O/FeCl₃. Further, the morphology, structure and composition of Fe_x(PO₄)_y(OH)_z·nH₂O microcrystals were also investigated by x‐ray diffraction (XRD), x‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) techniques. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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.     

On the crystal structure type of 2 CsCl · CoCl2 · 2 H2O

The following three-component systems have been studied: CsCl MnCl₂ H₂O at 25 °C; 2 CsCl · CuCl₂ · 2 H₂O—2 CsCl · CoCl₂ H₂O at 10 °C and 2 CsCl · MnCl₂ · 2 H₂O—2 CsCl · CoCl₂ H₂O at 25 °C and 10 °C. It was established that Co²⁺-ions do not substitute isodimorphously the Cu²⁺-ions in the tetragonal salt 2 CsCl · CuCl₂ · 2 H₂O, whereas in the case of the triclinic salt 2 CsCl · MnCl₂ · 2 H₂O they can substitute isodimorphously the Mn²⁺-ions. The theoretical considerations supported by the results obtained allow to predict the existence of the double salt 2 CsCl · CoCl₂ · 2 H₂O as well as the type of its crystal structure — triclinic, space group P1 .     

Crystallization of Calcium and Magnesium Phosphates from Solutions of Medium and Low Concentrations

Calcium phosphates are precipitated at 25 °C from solutions of medium (Ca = P = 50 mM) and low (Ca = P = 10 mM) concentrations in the presence of magnesium. Experiments are also performed with solutions in which Ca + Mg = P = 50 mM and Ca + Mg = P = 10 mM. An amorphous calcium phosphate, Ca₃ (PO₄)₂ · nH₂O, and brushite, CaHPO₄ · 2 H₂O, are the phases first nucleated. The phases occurring one year later are brushite in the more concentrated solutions, hydroxyapatite (Ca₅OH(PO₄)₃) and whitlockite (Ca₉MgH(PO₄)₇) in the others. Octacalciumphosphate, Ca₈H₂ (PO₄)₆ · 5H₂O, occurs as transitory phase. The effects of concentration, pH, supersaturation and magnesium on the precipitation and evolution of calcium phosphates, and the conditions for phase stability are discussed.     

The crystal structure of calcium aqua{ethylenediaminetetraacetato(3-)}nickelate(II) tetrahydrate,Ca[Ni(H<Emphasis Type="Italic">Edta</Emphasis>)(H<Subscript>2</Subscript>O)]<Subscript>2</Subscript>·4H<Subscript>2</Subscript>O

The crystal structure of Ca[Ni(HEdta)(H₂O)]₂ · 4H₂O (HEdta ^3?is a protonated anion of ethylenediaminetetraacetic acid) is determined. The unit-cell parameters are as follows: a = 7.706(1), b = 14.923(9), and c = 26.570(5) Å; V = 3055.6(2.4) ų; Z = 8; and space group Pbcn. Crystals are shaped as tetragonal prisms and colored green, which is not characteristic of this class of compounds. The structure is built of Ca²⁺ cations, octahedral [Ni(HEdta)(H₂O)]^? complex anions, and crystallization water molecules. In the complex anion, one of the acetate branches is free of coordination, whereas the remaining three branches coordinate the central atom forming glycinate metallocycles. The structure is based on sandwich layers, which are formed by networks of flat tetragonal Ca[Ni(HEdta)(H₂O)]₄(H₂O)₂ fragments adjoining one another by vertices.     

Equilibrium coefficients of co‐crystallization of M2+ ions with MgSeO4·6H2O and their dependences on various physicochemical factors

Equilibrium co‐crystallization coefficients of low amounts of M²⁺ions (M²⁺ = {Ni²⁺, Cu²⁺, Co²⁺, Zn²⁺, Mn²⁺, Cd²⁺}) with MgSeO₄·6H₂O at 25 °C have been determined. Their values are comprised in the range: 0.058 (for Cd) < k_eq < 1.57 (for Co) and depend on some physicochemical and crystal chemical properties of both: co‐crystallizing salts (MSeO₄·nH₂O) and co‐crystallizing ions (M²⁺). These dependences are sometimes such strong, that they make it possible to derive simple formulae permitting estimation of k_eq coefficients at average error not exceeding 17%. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of cadmium on crystallization of calcium phosphates

The precipitation of calcium phosphates in the presence of increasing cadmium amount was studied at 25 °C in dilute ammoniacal solutions ([Ca] = [P] = 0.005 M). An amorphous precipitate, an apatite‐like calcium phosphate and the compound Cd₅H₂(PO₄)₄·4H₂O are found according to pH and Cd concentration. The nucleation of hydroxyapatite is greatly delayed by cadmium, which influences also its crystallinity, but the effect tends to vanish with time. The role of cadmium is discussed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystallization of MIGe2(PO4)3 (MI – Na,K, Ag) from molten phosphate media

A number of NASICON‐related M^IGe₂(PO₄)₃ (M^I – Na, K, Ag) have been prepared using a high‐temperature solution method in the molten system M^I‐Ge‐P‐O (M^I – Na, K) based on the solubility data for GeO₂ at 1123 K for the Na‐P‐O system and 1173 K for the K‐P‐O one. The single crystals of AgGe₂(PO₄)₃ were obtained after crystallization of a melt with Ag/P = 1.4. It crystallizes in the trigonal system, space group R‐3, cell parameters a = 8.06340(1) Å, c = 21.8385(4) Å, Z = 6. The framework is built up from two GeO₆ units that are isolated from each other by PO₄ tetrahedra to form the main building block of the structure [Ge₂(PO₄)₃]⁻. Two types of silver cations M1 and M2 are found to have different coordination requirements shown by the bond valence sum calculations.     

Crystal chemistry of the salts Me+Cl · Me2+Cl2 · 2 H2O

The crystal chemistry of the double salts Me⁺Cl · Me²⁺Cl₂ · 2 H₂O (where (Me⁺ = K, Rb, Cs; Me²⁺ = Mn, Fe, Co, Ni) is considered. It is concluded that these salts crystallize in three types of structures, the Me⁺ ion size being decisive for the structure type. Salts containing the large Cs⁺ ions crystallize in an orthorhombic structure in which [Me²⁺ (H₂O)₂Cl₄] octahedra form chains having common Cl⁻ corners. Salts with the smaller K⁺ ions crystallize in a tricline system, the [Me²⁺ (H₂O)₂Cl₄] octahedra being connected by a common Cl–Cl edge and forming dimers. When the intermediate in size Rb⁺ ions are present in the salts, either of the above structures is possible as well as a monoclinic structure which is intermediate in symmetry. The expected isostructure of the cesium salts was checked by studing the CsCl · NiCl₂ · 2 H₂O–CsCl · MnCl₂ · 2H₂O–H₂O system. A continuous series of mixed crystals is found.     

Crystal structure and spectroscopic studies of a new organic monohydrogenmonophosphate dihydrate

The crystal synthesis and structure of a new organic monohydrogenmophosphate (3,4‐Cl₂‐CH₂C₆H₃NH₃)₂HPO₄·2H₂O are reported. This compound crystallizes in the monoclinic P2₁/n with a = 9.081(7) Å, b = 6.501(5) Å, c = 35.423(12) Å, β = 91.09(5)°, V = 2090.9(2) ų, and Z = 4. Crystal structure was solved and refined to R = 0.042, using 2543 independent reflections. It can be described by inorganic layers, including the HPO₄^‐ anions and the H₂O molecules, parallel to (a, b) planes and situated at z = 0 and z = 1/2. The interlayer spacing is occupied by the organic molecules which perform different interactions around the 3D network cohesion. A characterization of this compound by solid‐state (¹³C, ³¹P) MAS NMR and IR spectroscopies is also reported. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure of a new neodymium hexamolybdotellurate,Nd<Subscript>2</Subscript>TeMo<Subscript>6</Subscript>O<Subscript>24</Subscript> · 19H<Subscript>2</Subscript>O

The crystal structure of a new compound, namely, Nd₂TeMo₆O₂₄ · 19H₂O, is determined using X-ray diffraction. The crystal has a chain structure and consists of [Nd₂TeMo₆O₂₄ · 14H₂O]_n neutral chains aligned parallel to the [010] direction and crystallization water molecules. In a chain, each Nd atom links two heteropoly anions. The Nd³⁺ environment includes seven water molecules and two oxygen atoms of the two heteropoly anions adjacent in the chain. The polyhedron is a monocapped tetragonal antiprism. In the previously studied complex of similar composition, namely, Nd₂TeMo₆O₂₄ · 18H₂O, the Nd coordination polyhedron has the shape of a tricapped trigonal prism formed by six water molecules and three oxygen atoms of the two heteropoly anions adjacent in the chain.     

Crystal structure,thermal analysis and IR spectroscopy investigations of N,N‐dimethyl‐1,3‐propanediammonium monohydrogenmonophosphate trihydrate

A new organic monohydrogenmonophosphate (C₅H₁₆N₂)HPO₄.3H₂O (abbreviate as MPAP) is prepared by reacting H3PO4 with N, N‐dimethyl‐1,3‐propanediamine. This compound crystallizes in the orthorhombic crystal system, space group Pca2₁. Unit cell parameters are a % 8.1445(1) Å, b % 11.7734(2) Å, c % 12.9021(2) Å, with, Z % 4 and ρ_m % 1.31 g cm⁻³. The structure was solved, using the direct methods and refined against F² to a reliability R factor of 0.0257. Three types of hydrogen bonds participate to the structural cohesion: O(P)—H…O, O(W)—H…O and N—H…O. The first one connects HPO₄ groups in infinite chains. This organization of the phosphoric groups creates voids in which are located the water molecules which are themselves connected by the second type of hydrogen bonds to the adjacent phosphoric groups that lead to a typical layer organization of a polyanion [HPO₄.(H₂O)₃ ]²ⁿ⁻_n. The third hydrogen bond type is responsible for the cohesion between the two‐dimensional polyanions. Thus, a framework in a threedimensional way is then created. The thermal decomposition of MPAP shows a large endothermic effect corresponding to the elimination of the water molecules and a set of endotherms which are probably due to the evolution of ammonia from the structure and the decomposition. The title compound was also characterized by IR spectroscopy, the interpretation of the spectra is based on theoretical analyses and literature data. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electron paramagnetic resonance of Gd3+ in Eu2Zn3(NO3)12·24H2O single crystals

Electron paramagnetic resonance of Gd³⁺ in Eu₂Zn₃(NO₃)₁₂·24H₂O single crystals is studied at ≈9.45 GHz and at 298 and 77 K. Gd³⁺ substitutes for the Eu³⁺ site. In addition to the allowed fine structure lines, forbidden transitions (ΔM = ±2,±3,±4,±5) are observed. The superposition model is applied to the zero‐field splitting parameter b₂⁰. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hydrothermal synthesis and formation of 4ZnO·B2O3·H2O whiskers via a new route

4ZnO·B₂O₃·H₂O whiskers were prepared from 2ZnO·3B₂O₃·3.5H₂O under hydrothermal process at 160 °C for 10 h. The synthesized product was characterized by XRD, SEM, TG‐DSC and FT‐IR. SEM results showed that the synthesized 4ZnO·B₂O₃·H₂O whiskers' length was about 3–10 μm and the diameter was 0.2–0.3 μm. Further study on the whiskers' growth process and mechanism showed that the formation of the whiskers went through three stages and the morphology of 4ZnO·B₂O₃·H₂O changed from irregular particles to rod‐like structures and finally to whiskers. The variation of the morphology of the 4ZnO·B₂O₃·H₂O whisker with the concentration of the starting material was investigated. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and the crystal and molecular structures of a germanium(IV)-copper(II) heteronuclear diethylenetriaminepentaacetate complex, [Cu(μ-H<Emphasis Type="Italic">Dtpa</Emphasis>)<Subscript>2</Subscript>{Ge(OH)}<Subscript>2</Subscript>] · 12H<Subscript>2</Subscript>O

A procedure for synthesizing a mixed Cu-Ge complex with diethylenetriaminepentaacetic acid (H₅Dtpa) is worked out, the compound [Cu{Ge(OH)(HDtpa)}₂] · 12H₂O is synthesized, and its crystal structure is studied by X-ray diffraction. In the centrosymmetric trinuclear molecular complex, the octahedral coordination of the peripheral Ge atom involves three O and two N atoms of the HDtpa^4? ligand and the O atom of the hydroxo ligand. The central Cu atom is coordinated by four O and two N atoms of two HDtpa^4? ligands, which form a tetragonal bipyramid (4 + 2). The HDtpa^4? ligand fulfills an octadentate hexachelate bridging function (3N, 5O). The molecular complexes and crystallization water molecules are linked by an extended hydrogen-bond network.     

The crystal structure of aluminium,iron (III), and gallium acid phosphites

The structures of three acid phosphites of trivalent metals [Al(HPO₃H)₃(H₂O)] · H₂O (I), K[Fe(HPO₃H₄)] (II), and Rb₃[Ga(HPO₃H)₆] (III) have been determined. Structure I is layered, complex anions [Fe(HPO₃H)₄]⁻ form polymer chains in structure II, and structure III is insular.     

Coarse crystal layer growth and liquid entrapment study with gradient freeze technology

The coarse crystal layer growth and liquid entrapment processes were investigated with gradient freeze technology in this paper. The research system was hemihydrate phosphoric acid (H₃PO₄·0.5H₂O) crystal‐phosphoric acid aqueous solution. The distribution coefficients of ions (Ca²⁺, Fe³⁺ and Na⁺) in this system were measured. The effect of supercooling degree gradient on layer growth and the effect layer growth rate on ions redistribution were studied. The result indicated that the layer growth rate increased with supercooling degree gradient as an exponential curve. The distribution coefficient tended to increase as an approximate ‘S’ curve when coarse crystal layer growth rate increased. The ‘three region’ theory was applied to explain this phenomenon. Each ion's diffusion parameter was obtained, which contributed to explain the separation differences between different ions. The work in this paper also indicated that layer crystallization was an effective separation technology for electronic grade phosphoric acid preparation.     

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)_0.5M_1.25(H₂O)_1.5[BP₂O₈]·H₂O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO₄, PO₄, and (MO₄)OM(H₂O)₂ groups with hexagonal, P 6₁ 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigation of the crystallization of the system KAl(Cr)(SO4)212 H2O under various conditions

The crystallization of the isomorphous system KAl(Cr)(SO₄)₂ · 12 H₂O under various conditions has been studied. It has been found that the rate of linear crystallization of the face (100) passes through a maximum on the interval of Cr³⁺ concentrations 0.02–0.08 g ions/l which is shifted to the right with increasing temperature. Under the same conditions, the equilibrium coefficient of distribution of the microcomponent D has been determined in single crystals. D decreases with the increase of the Cr³⁺ concentration and the crystallization temperature. These results can be explained with the formation of complexes of Cr³⁺ in the solution which decreases the active concentration of the ion and are selectively adsorbed on the face (100). At the same Cr³⁺ concentration (0.058 g ion/l), the temperature dependence of the rate of growth of the face (100), as well as the influence of supersaturation on the rate of growth of the faces (100) and (111), have been studied. The apparent activation energy of crystallization of the face (100) has been determined to be E = 11.2 Kcal. · mol⁻¹. The data obtained are compared with analogical results for pure KAl(SO₄)₂ 12 H₂O.