ZnF2 Research Articles

Order parameter criticality of the d = 3 random-field Ising antiferromagnet Fe0.85Zn0.15F2.

The critical exponent beta=0.16+/-0.02 for the random-field Ising model order parameter is determined using extinction-free magnetic x-ray scattering for Fe0.85Zn0.15F2 in magnetic fields of 10 and 11 T. The observed value is consistent with other experimental random-field critical exponents, but disagrees sharply with Monte Carlo and exact ground state calculations on finite-sized systems.

Mechanochemical Synthesis of Ternary Fluorides with Perovskite Structures

Abstract Mechanochemical synthesis of ternary zinc fluorides, AZnF3 (A = K, Na and NH4) with perovskite structures was attempted by grinding equimolar mixtures of zinc fluoride (ZnF2) and one of fluorides, i.e., potassium fluoride (KF), sodium fluoride (NaF) and ammonium fluoride (NH4F), respectively, in air using a planetary ball mill. The grinding enables us to synthesize these compounds, and the crystallinity of them is improved as the grinding progresses. The synthesized materials formed in the ground mixtures seem to be agglomerates of fine particles having diameters of about several tens nanometer.

Synchrotron X-ray analysis of the electron density in CoF2 and ZnF2

Accurate structure factors for small crystals of the rutile-type structures CoF(2), cobalt difluoride, and ZnF(2), zinc difluoride, have been measured with focused lambda = 0.8400 (2) A synchrotron X-radiation at room temperature. Phenomenological structural trends across the full series of rutile-type transition metal difluorides are analysed, showing the importance of the metal atom in the degree of distortion of the metal-F(6) octahedra in these structures. Multipole models reveal strong asphericities in the electron density surrounding the transition metals, which are consistent with expectations from crystal field theory and the structural trends in these compounds. Transition metal 3d-orbital populations were computed from the multipole refinement parameters, showing significant repopulation of orbitals compared with the free atom, particularly for CoF(2).

Thermodynamic modelling of magnesium fluoride precipitation in concentrated zinc sulphate environment

Most electrolytic zinc plants have to deal with dissolved magnesium in their process liquors as zinc sulphide concentrates contain small amounts of magnesium. Applied magnesium bleed method are generally expensive and environmetally unfriendly. Recently, a new approach was suggested and discussed in which magnesium fluoride is selectively precipitated from purified zinc sulphate solutions by addition of zinc fluoride solution. Magnesium fluoride can be converted into magnesium hydroxide with sodium hydroxide solution and regeneration of chemicals is accomplished by electrolysis of the resulting sodium fluoride solution in a membrane cell. In this paper, a thermodynamic model of the precipitating system is evaluated in order to predict the residual fluoride content of the solution as a function of pH and temperature. This is an important parameter as residual fluoride can cause detrimental effects in the electrowinning stage (pitting of the aluminium chatodes). The model predictions are compared with experimental data. The presented thermodynamic model is a tool that contributes to the determination of the optimum precipitation conditions.

Ordering in the dilute weakly anisotropic antiferromagnetMn0.35Zn0.65F2

The highly diluted antiferromagnet Mn(0.35)Zn(0.65)F2 has been investigated by neutron scattering in zero field. The Bragg peaks observed below the Neel temperature TN (approximately 10.9 K) indicate stable antiferromagnetic long-range ordering at low temperature. The critical behavior is governed by random-exchange Ising model critical exponents (nu approximately 0.69 and gamma approximately 1.31), as reported for Mn(x)Zn(1-x)F2 with higher x and for the isostructural compound Fe(x)Zn(1-x)F2. However, in addition to the Bragg peaks, unusual scattering behavior appears for |q|>0 below a glassy temperature Tg approximately 7.0 K. The glassy region T<Tg corresponds to that of noticeable frequency dependence in earlier zero-field ac susceptibility measurements on this sample. These results indicate that long-range order coexists with short-range nonequilibrium clusters in this highly diluted magnet.

Magnesium removal in the electrolytic zinc industry

Most electrolytic zinc plants have to deal with dissolved magnesium in their process liquors, as zinc sulphide concentrates contain small amounts of magnesium. Applied magnesium bleed methods are generally expensive and environmentally unfriendly. In this paper, a new approach is suggested and discussed in which magnesium fluoride is selectively precipitated from purified zinc sulphate solutions. The magnesium fluoride is contacted with sodium hydroxide solution and thus converted into magnesium hydroxide, which could be saleable product. It is shown that the resulting sodium fluoride solution can be electrolysed in a membrane cell consisting of a zinc anode and an inert cathode. This yields zinc fluoride and sodium hydroxide solutions, which both can be recycled to the magnesium removal process. Various experiments, which are discussed in this paper, confirm that the proposed process is possible.

Specific heat and optical birefringence ofFe0.25Zn0.75F2

The specific heat (Cm) and optical birefringence (\Delta n) for the magnetic percolation threshold system Fe(0.25)Zn(0.75)F2 are analyzed with the aid of Monte Carlo (MC) simulations. Both \Delta n and the magnetic energy (Um) are governed by a linear combination of near-neighbor spin-spin correlations, which we have determined for \Delta n using MC simulations modeled closely after the real system. Near a phase transition or when only one interaction dominates, the temperature derivative of the birefringence [{d(\Delta n)}/{dT}] is expected to be proportional Cm since all relevant correlations necessarily have the same temperature dependence. Such a proportionality does not hold for Fe(0.25)Zn(0.75)F2 at low temperatures, however, indicating that neither condition above holds. MC results for this percolation system demonstrate that the shape of the temperature derivative of correlations associated with the frustrating third-nearest-neighbor interaction differs from that of the dominant second-nearest-neighbor interaction, accurately explaining the experimentally observed behavior quantitatively.

Equilibrium Random-Field Ising Critical Scattering in the AntiferromagnetFe0.93Zn0.07F2

It has long been believed that equilibrium random-field Ising model (RFIM) critical scattering studies are not feasible in dilute antiferromagnets close to and below Tc(H) because of severe non-equilibrium effects. The high magnetic concentration Ising antiferromagnet Fe(0.93)Zn(0.07)F2, however, does provide equilibrium behavior. We have employed scaling techniques to extract the universal equilibrium scattering line shape, critical exponents nu = 0.87 +- 0.07 and eta = 0.20 +- 0.05, and amplitude ratios of this RFIM system.

Fluoroaluminate glass containing Cd, Zn, and La fluorides

In order to obtain glass with an increased index of refraction, oxygen-free fluoroaluminate glass samples containing cadmium, zinc, and lanthanum fluorides were synthesized. Their main physicochemical properties were studied. According to the data from x-ray phase analysis cadmium, zinc, and lanthanum fluorides do not form crystal phase matrices with the components and are present in the form of independent phases. The optical constants of this glass vary within the range of 1.4278–1.4303 at an aperture of 0.1.

Synthese von 2,2-DiphenylethyI-substituierten Silanen -Molekülstruktur von Trichlor-2,2-diphenylethylsilan /Syntheses of 2,2-Diphenylethyl-Substituted Silanes -Molecular Structure of Trichloro-2,2-diphenylethylsilane

Abstract Hydrosilylation of 1,1-diphenylethylene with trichlorosilane leads in high yields to trichloro-2.2-diphenylethylsilane (1), which was investigated spectroscopically as well as by X-ray structure determination. The compound crystallizes monoclinically in the acentric space group Cc {a = 1002.4, b = 1573.8, c = 979.7 pm, β = 106.27°, Z = 4}; the bonding parameters show no special features. By fluorination with zinc(II) fluoride in diethylether and by reduction with “Red-Al” in toluene, the corresponding SiF3 (2) and SiH3 derivatives (3) are received, respectively.

Alkali fluorozirconate glasses

Glass formation was investigated in fluoride systems based on ZrF 4 in association with aluminum and zinc fluoride and containing large amounts of alkali fluorides. Properties of the glasses including chemical durability in the 50(ZrF 4–ZnF 2–AlF 3)–5YF 3–10BaF 2–35LiF system were measured. Then lithium fluoride was substituted by NaF and KF in the 20ZrF 4–10ZnF 2–20AlF 3–5YF 3–10BaF 2–35LiF glass. Finally, glass formation in the pseudo ternary system 85(ZrF 4–NaF–LiF)–5AlF 3–10BaF 2 was investigated. Glasses with refractive index equal to 1.445 could be obtained. Glass transition temperature ranges from 200 to 265°C for glasses containing 35 to 45 mol% in alkali fluorides.

Effect of LnF3(Ln = Y, La, Gd and Yb) on the properties of ZnF2–ZrF4–AlF3glasses

Effect of LnF₃(Ln = Y, La, Gd and Yb) on the properties of ZnF₂–ZrF₄–AlF₃glasses

(enH2)0.5][Zr2(PO4)2(HPO4)F]·H2O: A Unique Zirconium Fluoride Phosphate with a Cavity Structure

Medium-sized channels pass through the structure of the first zinc fluoride phosphate (section of the structure is shown on the right). The framework is constructed from ZrO6 and ZrO5F octahedra and PO4 and PO3(OH) tetrahedra. Further cavity-containing compounds of this type should be accessible by variation of the amine used as a template.

Facile syntheses of tris(trifluoromethyl)phosphine and difluorotris (trifluoromethyl) phosphorane

Tris(trifluoromethyl) phosphine is easily available in high yield using the three component system D(NAt) 2) 3/NF 3Ar/(DhI) 3D in IIDA. Addition of chlorine and fluorination with zinc difluoride yield difluorotris (trifluoromethyl) phosphorane.

Investigation of the post-hardening reaction in glass-ionomer cements based on poly(vinyl phosphonic acid)

In this study the behaviour of two PVPA-based glass-ionomer cements was investigated. The first cement was prepared from PVPA homopolymer and glass, together with a reaction modifier. In the second cement a modified version of the polymer was used instead of the homopolymer. The modification was achieved by the treatment of the polymer with a small quantity of zinc fluoride. The effect of ageing under different conditions on the strength, mass and volume of the cements was determined. The ZnF2-containing system behaved in a fairly straightforward manner, showing a gradual increase in strength with time (up to 3 months) that was similar to glass-ionomer cements based on poly(acrylic acid). By contrast the unmodified material did not increase in strength with time, a feature that was attributed to extensive crosslinking of the material, causing it to become more brittle and hence more sensitive to defects in the specimens. With regard to the effect on mass and volume, both types of cement behaved like typical set glass-ionomers, displaying a sensitivity to dessication but little, if any, sensitivity to aqueous media.

Simple preparation of difluorophosphoranes using anhydrous zinc and tetramethylammonium fluorides

Bromophosphonium bromides, R 3PBr +Br − (R= nBu, NMe 2, NEt 2) are easily fluorinated using zinc difluoride in pyridine or tetramethylammonium fluoride in methylene chloride to give the corresponding difluorophosphoranes R 3PF 2 in high yield. A simple procedure for preparing pure tetramethylammonium fluoride is described.

Theoretical calculations of electron densities in zinc chalcogenides and in zinc fluoride

Self-consistent, non-relativistic Hartree-Fock calculations on a finite cluster of atoms with zinc at the center have been performed on the zinc blende compounds ZnTe, ZnSe, ZnS, on ZnO (wurtzite structure), ZnO (NaCl structure), and on ZnF2 (rutile-type structure) to obtain changes in s electron density Δρ(0) at the67Zn nucleus. We solved the eigenvalue problem of the dynamic matrix to calculate the second-order Doppler shiftSSOD using appropriate force constant models and determined the isomer shiftS from the measured center shift for each compound. Our calculations clearly show the importance of the covalency of the Zn-ligand bond for the origin ofS and fully corroborate the experimental linear correlations between decreasingS values and increasing electronegativity of the ligands. The most important contribution to Δρ(0) comes from the Zn(4s) electrons, with a smaller but significant contribution from the Zn(3s) electrons. For the change of the mean-square nuclear charge radius for the Mossbauer transition in67Zn, we obtain Δ〈r2〉=+(13.9±1.4) × 10−3 fm2.

Electrical Conductivity of Amorphous Conductors on the Base of Zinc Fluoride

Electrical Conductivity of Amorphous Conductors on the Base of Zinc Fluoride

Defect creation in alkali-halides under dense electronic excitations: experimental results on NaCl and KBr

We present the results of simultaneous in situ luminescence and optical absorption studies of alkali-halides, submitted to very dense electronic excitations induced by swift heavy ion irradiations at low temperatures (15–200 K). X-ray irradiations performed in the same experimental conditions permit the necessary comparison with ion irradiations. The luminescence of the self-trapped excitons is only slightly modified by increasing the electronic stopping power, while new features appear for the point defect creation. For instance, in NaCl at 15 K, F centres are efficiently created by Ne, Zn and Xe irradiations and F2 centres only by Zn and Xe irradiations. We discuss the evolution of the yields of defect creation as a function of the temperature and of the electronic stopping power.

Oxidation State +IV in Group 12 Chemistry. Ab Initio Study of Zinc(IV), Cadmium(IV), and Mercury(IV) Fluorides

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOxidation State +IV in Group 12 Chemistry. Ab Initio Study of Zinc(IV), Cadmium(IV), and Mercury(IV) FluoridesMartin Kaupp, Michael Dolg, Hermann Stoll, and Hans Georg von SchneringCite this: Inorg. Chem. 1994, 33, 10, 2122–2131Publication Date (Print):May 1, 1994Publication History Published online1 May 2002Published inissue 1 May 1994https://doi.org/10.1021/ic00088a012RIGHTS & PERMISSIONSArticle Views464Altmetric-Citations70LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts