Beiträge zum thermischen Verhalten und zur Kristallchemie von wasserfreien Phosphaten XXXII [1] Neue Orthophosphate des zweiwertigen Chroms — Mg3Cr3(PO4)4, Mg3, 75Cr2, 25(PO4)4, Ca3Cr3(PO4)4 und Ca2, 00Cr4, 00(PO4)4

Contributions on Crystal Chemistry and Thermal Behaviour of Anhydrous Phosphates. XXXII. New Orthophosphates of Divalent Chromium — Mg₃Cr₃(PO₄)₄, Mg_{3, 75}Cr_{2, 25}(PO₄)₄, Ca₃Cr₃(PO₄)₄ and Ca_{2, 00}Cr_{4, 00}(PO₄)₄ Solid state reactions via the gas phase led in the systems A₃(PO₄)₂ / Cr₃(PO₄)₂ (A = Mg, Ca) to the four new compounds Mg₃Cr₃(PO₄)₄ ( A ), Mg_3.75Cr_2.25(PO₄)₄ ( B ), Ca₃Cr₃(PO₄)₄ ( C ), and Ca_2.00Cr_4.00(PO₄)₄ ( D ). These were characterized by single crystal structure investigations [( A ): P2₁/n, Z = 1, a = 4.863(2) Å, b = 9.507(4) Å, c = 6.439(2) Å, β = 91.13(6)°, 1855 independend reflections, 63 parameters, R1 = 0.035, wR2 = 0.083; ( B ): P2₁/a, Z = 2, a = 6.427(2) Å, b = 9.363(2) Å, c = 10.051(3) Å, β = 106.16(3)°, 1687 indep. refl., 121 param., R1 = 0.032, wR2 = 0.085; ( C ): P‐1, Z = 2, a = 8.961(1) Å, b = 8.994(1) Å, c = 9.881(1) Å, α = 104.96(2)°, β = 106.03(2)°, γ = 110.19(2)°, 2908 indep. refl., 235 param., R1 = 0.036, wR2 = 0.111; ( D ): C2/c, Z = 4, a = 17.511(2) Å, b = 4.9933(6) Å, c = 16.825(2) Å, β = 117.95(1)°, 1506 indep. refl., 121 param., R1 = 0.034, wR2 = 0.098]. The crystal structures contain divalent chromium on various crystallographic sites, each showing a (4+n)‐coordination (n = 1, 2, 3). For the magnesium compounds and Ca_2.00Cr_4.00(PO₄)₄ a disorder of the divalent cations Mg²⁺/Cr²⁺ or Ca²⁺/Cr²⁺ is observed. Mg_3.75Cr_2.25(PO₄)₄ adopts a new structure type, while Mg₃Cr₃(PO₄)₄ is isotypic to Mg₃(PO₄)₂. Ca₃Cr₃(PO₄)₄ and Ca_2.00Cr_4.00(PO₄) ₄ are structurally very closely related and belong to the Ca₃Cu₃(PO₄)₄‐structure family. The orthophosphate Ca₉Cr(PO₄)₇, containing trivalent chromium, has been obtained besides C and D .     

Quantum chemical and spectroscopic analysis of calcium hydroxyapatite and related materials

Amorphous calcium hydroxyapatite was examined by vibrational spectroscopy (Raman and infra-red (IR)) and quantum chemical simulation techniques. The structures and vibrational (IR, Raman and inelastic neutron scattering) spectra of PO₄³⁻ ion, Ca₃(PO₄)₂, [Ca₃(PO₄)₂]₃, Ca₅(PO₄)₃OH, CaHPO₄, [CaHPO₄]₂, Ca₃(PO₄)₂·H₂O, Ca₃(PO₄)₂·2H₂O and Ca₃(PO₄)₂·3H₂O clusters were quantum chemically simulated at ab initio and semiempirical levels of approximation. A complete coordinate analysis of the vibrational spectra was performed. The comparison of the theoretically simulated spectra with the experimental ones allows to identify correctly the phase composition of the amorphous calcium hydroxyapatite and related materials. The shape of the bands in the IR spectra of the hydroxoapatite can be used in order to characterize the structural properties of the material, e.g., the PO₄³⁻ ion status, the degree of hydrolysis of the material and the presence of hydrolysis products.     

Phase equilibria in the tricalcium phosphate-mixed calcium sodium (potassium) phosphate systems

Phase equilibria in the quasi-binary sections Ca₃(PO₄)₂-CaMPO₄ (M = Na, K) are distinguished by high-temperature isomorphism of glaserite-like phases α’-Ca₃(PO₄)₂ and α-CaMPO₄. The main differences of the Ca₃(PO₄)₂-CaKPO₄ system from the Ca₃(PO₄)₂-CaNaPO₄ system are a shift of invariant equilibria toward higher temperatures, deceleration of phase transformations, and the emergence of polymorphism of an intermediate phase of an ordered solid solution based on α-CaKPO₄. The low-temperature modification of this phase of a composition near Ca₈K₂(PO₄)₆ has the apatite structure with unoccupied hexagonal channels.     

Einige Cadmiumapatite sowie die Verbindungen Cd2XO4F mit X = P,As und V

The Cadmiumapatites Cd₅(PO₄)₃OH und Cd₅(PO₄)₃F as well as the yet unknown iodoapatite Cd₅(VO₄)₃I were synthesized and investigated by X-ray powder and single crystal methods. All single crystal diagrams exhibit hexagonal symmetry. The iodine compound has such a low c constant (about 6.5 Å) that is seems essential to discuss the halide positions in the structure. The reflexions of Cd₅(PO₄)₃F show splitting which is indicative of a triclinic distortion of the apatite structure and of twinning. At about 150–350°C the deformation disappears reversibly. Cd₅(AsO₄)₃F, Cd₅(VO₄)₃F and the corresponding OH-compounds could not be prepared, but the new isotypic compounds Cd₂XO₄F (X = P, As, V) were synthesized by thermal and hydrothermal reactions. Single crystal investigations and the morphology of Cd₂PO₄F proved the space group C2/c. There are structural relations to the minerals of the wagnerite group. In connexion with the synthesis of Cd₂XO₄F a discussion of the relative stabilities of different apatites is given.     

Eu luminescence—a structural probe in BiCa4(PO4)3O, an apatite related phosphate

Eu³⁺ luminescence is studied in apatite-related phosphate BiCa₄(PO₄)₃O. Compositions of the formula Bi_1−xEu_xCa₄(PO₄)₃O [x=0.05, 0.1, 0.3, 0.5, 0.8 and 1.0] are synthesized and they are isostructural with parent BiCa₄(PO₄)₃O. Room temperature photoluminescence shows the various transitions ⁵D₀→⁷F_J(=0,1,2) of Eu³⁺. The emission results of compositions with different Eu³⁺ content show the difference in site occupancy of Eu³⁺ in Bi_1−xEu_xCa₄(PO₄)₃O. The intense ⁵D₀-⁷F₀ line at 574 nm for higher Eu³⁺ content is attributed to the presence of strongly covalent Eu-O bond that is possible by substituting Bi³⁺ in the Ca(2) site. This shows the preferential occupancy of Bi³⁺ in Ca(2) site and this has been attributed to the 6s² lone pair electrons of Bi³⁺. This is further confirmed by comparing the emission results with La_0.95Eu_0.05Ca₄(PO₄)₃O.     

Synthesis and characterization of phosphates in molten systems Cs2O-P2O5-CaO-M2O3 (M—Al, Fe, Cr)

The crystallization of complex phosphates from the melts of Cs₂O-P₂O₅-CaO-M^III₂O₃ (M^III—Al, Fe, Cr) systems have been investigated at fixed value Cs/P molar ratios equal to 0.7, 1.0 and 1.3 and Са/Р=0.2 and Ca/М^III=1. The fields of crystallization of CsCaP₃O₉, β-Ca₂P₂O₇, Cs₂CaP₂O₇, Cs₃CaFe(P₂O₇)₂, Ca₉M^III(PO₄)₇ (M^III—Fe, Cr), Cs_0.63Ca_9.63Fe_0.37(PO₄)₇ and CsCa₁₀(PO₄)₇ were determined. Obtained phosphates were investigated using powder X-ray diffraction and FTIR spectroscopy. Novel whitlockite-related phases CsCa₁₀(PO₄)₇ and Cs_0.63Ca_9.63Fe_0.37(PO₄)₇ have been characterized by single crystal X-ray diffraction: space group R3c, a=10.5536(5) and 10.5221(4) Å, с=37.2283(19) and 37.2405(17) Å, respectively.     

Optical,thermal, and magnetic properties of a microporous fluorinated iron phosphate: (H3O)2[Fe4(H2O)2F4(PO4)2(HPO4)2](H2O)

The non-centrosymmetric microporous fluorinated iron phosphate, (H₃O)₂[Fe₄(H₂O)₂F₄(PO₄)₂(HPO₄)₂](H₂O), is endowed with properties. In fact, the thermogravimetric analysis study shows a mass loss evolution as a temperature function. The optical study was also examined by UV–vis absorption. The magnetic results reveal the appearance of a ferromagnetic behavior at low temperature (Tc = 11.64 K).     

Investigating the Crystallization Process of Boron-Bearing Silicate-Phosphate Glasses by Thermal and Spectroscopic Methods

Glasses and devitrificates from the SiO₂–B₂O₃–P₂O₅–K₂O–CaO–MgO system with constant contents of SiO₂ and P₂O₅ network formers, modified by the addition of B₂O₃, were analyzed. All materials were synthesized by the traditional melt-quenching technique. The glass stability (GS) parameters (K_rg, ∆T, K_W, K_H) were determined. The effect of the addition of B₂O₃ on the GS, liquation phenomenon, crystallization process, and the type of crystallizing phases were examined using SEM-EDS, DSC, XRD, and Raman spectroscopy imaging methods. It was observed that the addition of B₂O₃ increased the tendency of the glass to crystallize. Both phosphates (e.g., Ca₉MgK(PO₄)₇, Mg₃Ca₃(PO₄)₄), and silicates (e.g., K₂Mg₅(Si₁₂O₃₀), CaMg(Si₂O₆), MgSiO₃) crystallized in the studied system. The Raman spectrum for the orthophosphate Mg₃Ca₃(PO₄)₄ stanfieldite type was obtained. Boron ions were introduced into the structures of crystalline compounds at high crystallization temperatures. The type of crystallizing phases was found to be related to the phenomenon of liquation, and the order of their occurrence was dependent on the Gibbs free enthalpy.     

Verbindungen des Typs MII3MIII(PO4)3 mit Eulytinstruktur (MII = Pb,Sr, Ba; MIII = La,Lanthanide, Y,Sc, Bi,In, TI)1

A number of new phosphates of the formula M^II₃M^III(PO₄)₃ has been prepared. They have the cubic structure of eulytite (Bi₄(SiO₄)₃). Obviously all combinations of the cations being specified in the title for M^II and M^III seem to be possible; moreover, Ca₃Bi(PO₄)₃ does exist. The ions M^II and M^III are distributed on the positions of Bi in a statistical manner. The peculiar dependence of the lattive constants of the lanthanide compounds Pb₃Ln(PO₄)₃ (including La) on the (Atomic number of the lanthanide ions suggests the conclusion that the small trivalent cations (r < 1 Å) do not have a close contact with the surrounding oxygen ions forming a distorted octahedron.     

Contribution a l'etude des systemes Ca3(PO4)2-MSO4 (M=Sr,Ba)

In the systems Ca₃(PO₄)₂-MSO₄ (M = Sr, Ba), the series of single phase Ca_21?3xM_2xI(PO₄)_14?2x(SO₄)_2x with 0<x<0.15 forM=Sr and 0<x<0.1 forM = Ba have been prepared. These solid solutions, respectively strontium phosphosulfate and barium phosphosulfate, are isostructural with anhydrous tricalcium orthophosphate. They have been characterized by their infrared spectra and their crystallographic unit cell parameters.     

Heat Conductivity of Zirconium and Alkali Metal (Na,Cs) Phosphates of the NaZr2(PO4)3 Family

The heat conductivity of porous Zr₃(PO₄)₄, NaZr₂(PO₄)₃, CsZr₂(PO₄)₃, and Na₅Zr(PO₄)₃ samples was studied in the range 298-673 K. The heat conductivity coefficients of the zero-porosity phosphates under study were calculated and prospects for their application were considered.     

Über die Löslichkeit schwerlöslicher Salze,insbesondere gefällter Calciumphosphate

Zusammenfassung Schwerlösliche Salze (z. B. viele Hydroxide, Sulfide, Phosphate) liegen in der Fällungsform als äußerst feindisperse, kolloide Anteile mit meist nicht stöchiometrischer Zusammensetzung vor. Das Löslichkeitsverhalten der Substanzen weicht unter diesen Bedingungen von dem der kristallisierten Formen ab. Die hierbei auftretenden Reaktionstypen und die bisher bekannten quantitativen Beziehungen werden an Ca₅(PO₄)₃OH und Ca₄H(PO₄)₃·2H₂O diskutiert.

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Precipitations of salts of low solubility (hydroxides, sulfides, phosphates) have primary the form of extremely fine colloidal dispersions, usually not of stoichiometric composition. The solubility behaviour of substances under these conditions is different from the behaviour of the crystalline phases. Thereby occurring types of reactions and already known quantitative relations are beeing discussed, using Ca₅(PO₄)₃OH and Ca₄H(PO₄)₃·2 H₂O as examples.

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Mit 18 Abbildungen

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Unter Mitarbeit vonHelga Schmidt. Mit Unterstützung der Deutschen Forschungsgemeinschaft, Bad Godesberg. Anschrift des Verfassers: Priv.-Doz. Dr.Heinrich Newesely, Forschungsgruppe für Mikromorphologie im Fritz-Haber-Institut (Max-Planck-Gesellschaft), 1 Berlin 33, Dahlem, Faradayweg 16.     

Organic radicals in natural apatites according to EPR data: Potential genetic and paleoclimatic indicators

In a group of natural marine apatites Ca₅(PO₄)₃(F, OH), organic ?H₃, ?H₂—R, HO?HR, (CH₃)₂—?R, and —?_org radicals are identified by EPR. The relation between the EPR spectra of the observed organic radicals, the valence form, and the structural location of impurity vanadium ions (V⁴⁺ (VO²⁺) on the Ca²⁺ II site or V⁵⁺ (VO₄)^3- → (PO₄)^3-) is established. The structure of organic radicals correlates with the type of organic matter in the sample under analysis: sapropelic or humic, depending on the climatic conditions of mineral genesis.     

Mechanochemical synthesis of nanostructured fluorapatite/fluorhydroxyapatite and carbonated fluorapatite/fluorhydroxyapatite

Powder mixture of Ca(OH)₂-P₂O₅-CaF₂ were milled in planetary ball mill. A carbonated fluorhydroxyapatite, FHA Ca₁₀(PO₄)_1−y(CO₃)_y(PO₄)₅(OH)_2−2x1(F)_2x1 was formed after 5 h of milling and carbonated fluoroapatite Ca₁₀(PO₄)_1−y(CO₃)_y(PO₄)₅(F)₂ was formed after 9 h of milling. Complete transformation of the carbonated form of FA into then single phase of FA occurred after 9 h milling and thermally treating. The various experimental techniques like X-ray Diffraction (XRD), Differential Thermal Analysis (DTA), Infrared Spectroscopy (IR), Transmission Electron Microscopy and Scanning Electron Microscopy (SEM) were used to characterize the synthesized powders and to postulate reaction mechanisms’ steps- transformations of reactants involved.     

Characterization of sol-gel processing of calcium phosphate thin films on silicon substrate by FTIR spectroscopy

Calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, CHAp) films were obtained on silicon substrates by a sol-gel method using a spin-coating technique. In the sol-gel process, ethylendiamintetraacetic acid and 1,2-ethandiol, triethanolamine and polyvinyl alcohol were used as complexing agents and gel network forming agents, respectively. The samples were annealed at 1000 °C for 5 h in air after each spinning procedure. Spin-coating and annealing procedures were repeated 5, 8 and 10 times. The coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDX) and Fourier Transform infrared spectroscopy (FTIR). FTIR-spectroscopy allowed us to predict the formation of oxyhydroxyapatite Ca₁₀(PO₄)₆(OH)_2-2xO_x on the Si substrate. Moreover, according to the FTIR results, the side phase β-Ca₃(PO₄)₂ has been formed instead of α-Ca₃(PO₄)₂. In addition, the anhydrous dicalcium, phosphate phase CaHPO₄ was also detected spectroscopically.     

Apatites of divalent europium

The preparation methods of Eu₃(PO₄)₂, Eu₅(PO₄)₃F, Eu₃(PO₄)Cl and Eu₅(AsO₄)₃OH are described. Eu₃(PO₄)₂ crystallizes in a rhombohedral unit cell and the apatite like compounds in the $\text{P6}{}_3\text{m}$ hexagonal structure. All the compounds are isomorphous with the corresponding Sr compounds, and similar in size. Magnetic susceptibility measurements show that Eu₃(PO₄)₂ is magnetically ordered below 5 K and Eu₅(PO₄)₃F and Eu₅(PO₄)₃Cl are paramagnetic. Solid solution of the Eu_5?xCa_x(PO₄)₃F system obey Vegard's law, while the Eu_5?xBa_x(PO₄)₃F and Eu_5?xBa_x(PO₄)₃Cl systems show a trend to form ordered solid solutions.     

The system YPO4Ca3(PO4)2Ca2P2O7

The ternary system YPO₄Ca₃(PO₄)₂Ca₂P₂O₇ has been investigated by differential thermal analysis, powder X-ray diffraction, and microscopy in reflected light. Its phase diagram and isothermal section at room temperature have been determined. The system contains only one double phosphate which is formed at the 1:1 molar ratio YPO₄:Ca₃(PO₄)₂, i.e., Ca₃Y(PO₄)₃.     

The system Y2O3−CaO−P2O5

The ternary system Y₂O₃?CaO?P₂O₅ has been examined by DTA, X-ray diffraction, IR and microscopic methods. Its phase diagram has been provided within the composition range YPO₄?Ca₃(PO₄)₂?P₂O₅. The occurrence of four mixed phosphates: Ca₃Y(PO₄)₃, CaYP₃O₁₀, CaY(PO₃)₅, Ca₂Y(PO₃)₇ has been discovered in the system. Basic X-ray data have been determined for these newly discovered compounds and several methods of their synthesis developed.     

Die Kristallstruktur von Ca9(Ca x Mg1−x )(AsO4)6(AsO3OH) mitx ∼ 0,5

The crystal structure of Ca₉(Ca _x Mg_1–x )(AsO₄)₆(AsO₃OH) withx 0.5 (a=10.73,c=37.74 Å; space group R3c-C _3v ⁶ ;Z=6) was solved from 985 independent X-ray intensities collected on a 4-circle diffractometer, and refined toR=5.7% for all data. This compound is isotypic to Ca₉Mg(PO₄)₆(PO₃OH), a structure of the whitlockite-type.

     

Crystallographic studies of the role of Mg as a stabilizing impurity in β-Ca3(PO4)2. The crystal structure of pure β-Ca3(PO4)2

β-Ca₃(PO₄)₂ crystallizes in the rhombohedral space group R3c with unit cell parameters a = 10.439(1), c = 37.375(6) Å (hexagonal setting) and cell contents of 21 [Ca₃(PO₄)₂]. The structure was refined to R_w = 0.026, R = 0.030 using 1143 X-ray intensities collected from a single crystal by counter methods. Corrections were made for absorption, secondary extinction, and anomalous dispersion.The structure is related to that of Ba₃(VO₄)₂, but has lower symmetry because of the widely different ionic sizes of Ca and Ba. Seven [Ca₃(PO₄)₂] units occupy a volume corresponding to eight [Ba₃(PO₄)₂] units. The requirement of the c glide in β-Ca₃(PO₄)₂ has been shown in the least squares refinements to be attained by disorder of one cation over two sites. This disorder has a far-reaching effect on the structure.