Manganese Fluoride Research Articles

A Study of Cobalt and Manganese Fluorides as Cathode Materials for Rechargeable Lithium Cells

This paper describes a study of the lithium/transition metal fluoride cells using nanocomposites of carbon with cobalt or manganese fluorides as cathode materials. The nanocomposite cathode materials were prepared by high energy milling of carbon and metal fluorides. It was, however, found that cobalt trifluoride reacted with carbon during the high energy milling process to form carbon fluoride. The Li/cobalt fluoride cells were, therefore, studied by using nanocomposite cathodes prepared by high energy milling of carbon, cobalt metal and lithium fluoride or cathodes prepared by mixing carbon and cobalt trifluoride without subjecting the mixture to the high energy milling process. The charge- discharge characteristics of lithium/transition metal fluoride cells were studied at 22oC and 50oC using a 1M LiPF6-sulfolane solution as the electrolyte. The cells were found to be electrochemically reversible but could not be completely charged due to simultaneous oxidation of the electrolyte at potentials above ~4.5 Volts.

A Study of Cobalt and Manganese Fluorides as Cathode Materials for Rechargeable Lithium Cells

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Theoretical study on the effects of oxygen doping on the lithium ion conductive perovskite‐type manganese fluoride of KxBa(1−x)/2MnF3

AbstractPreviously, we demonstrated that the lithium ion conduction in the perovskite‐type manganese fluoride is attributed to counter cation‐site vacancy mechanism. The divalent counter cation‐doped KxBa(1−x)/2MnF3 was theoretically predicted as the lithium ion conductor in the perovskite‐type manganese fluoride. In this study, we considered the oxygen doping for KxBa(1−x)/2MnF3 to realize the higher lithium ion conductivity. It is because lithium ion forms the stronger ionic bond with the doped oxygen anion. The hybrid‐DFT calculations were performed to investigate the lithium ion conduction in the oxygen‐doped KxBa(1−x)/2MnF3. The calculation results were discussed from the viewpoints of the potential energy curve, electron densities, and charge and spin densities. The effect of the lithium ion fluctuation was also discussed by calculating the ratio of the diffusion coefficients. Finally, we theoretically predicted the ideal oxygen‐doped structure for KxBa(1−x)/2MnF3. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009

The theoretical study for the perovskite-type manganese fluorides of KMnF 3, RbMnF 3 and K 1−xLi xMnF 3

We performed the hybrid-density functional theory (DFT) calculations for the strongly correlated perovskite-type manganese fluorides of KMnF 3, RbMnF 3 and K 1− x Li x MnF 3 In both solids, UBHHLYP, which contains 50% Hartree–Fock exchange term, provided the reasonable effective exchange integral ( J ab ) values, in comparison with the experimental ones. In order to investigate the intrinsic roles of counter cations precisely, we examined the variations of the total energy and J ab value, assuming the displacement of counter cation toward <1 0 0> direction. In KMnF 3 (RbMnF 3), it was found that the steric repulsion between potassium (rubidium) and bottleneck is large, while that between lithium and bottleneck is negligible in K 1− x Li x MnF 3. Finally, we also showed the possibility of the lithium ion conduction in the antiferromagnetic K 1− x Li x MnF 3. It was concluded that the lithium ion conduction in RMnF 3 is possible, if the vacancy at R site exists.

Magnetic linear dichroism of an antiferromagnetic MnF2 crystal: Oddness in two different antiferromagnetic states

Dichroism of linearly polarized light propagating along the tetragonal C4 axis, induced by a longitudinal magnetic field, has been revealed in a tetragonal antiferromagnetic manganese fluoride crystal in the region of optical transitions. The magnetic linear dichroism observed is proportional to the magnetic field strength and odd with respect to the field sign. The value of the effect is sufficient for optical observation of antiferromagnetic domains in MnF2 crystals.

Characteristics of F doped PZT ceramics using different fluorine sources

In this study, some structural and electrical properties of a PZT base composition Pb 0.89(Ba, Sr) 0.11(Zr 0.52Ti 0.48)O 3 co-doped with 1 mol% manganese and 2 mol% fluorine have been studied. Two different fluorine sources were used: lead fluoride PbF 2 and manganese fluoride MnF 2. These fluoride salts are added to the co-precipitated precursors powder. Mn dopant was added to the solution as manganese acetate (MnAc) before co-precipitation, when PbF 2 was used. The structural analysis of the sintered ceramics revealed that MnF 2 doping makes the volume of the cubic unit cell ( V c) and the grain size decrease, whereas (MnAc, PbF 2) co-doping makes the apparent density increase and keeps the average grain size and V c unchanged. Both types of doping reagents largely enhance the piezoelectric activity (high d 33 and k 33 coefficients, well saturated Polarization–Electric field loops) but MnF 2 induces both combinatory soft and hard characteristics compared to (MnAc, PbF 2) co-doping. Impedance spectroscopy showed that both types of doping reagents strongly reduce the electrical conductivity with the same conducting species, i.e. the same defect chemistry, confirmed by optical absorption data. Finally, this study shows that in the semi-wet process used, PbF 2 is added homogeneously to the co-precipitated powder. Whatever the fluorine source, only the coexistence of Mn and F dopants is necessary to improve the piezoelectric response.

Reaction of C 60 with KMnF 4: Isolation and characterization of a new isomer of C 60F 8 and re-evaluation of the structures of C 60F 7(CF 3) and the known isomer of C 60F 8

The volatile fluorofullerene products of high-temperature reactions of C 60 with the ternary manganese(III, IV) fluorides KMnF 4, KMnF 5, A 2MnF 6 (A + = Li +, K +, Cs +), and K 3MnF 6 were monitored as a function of reaction temperature, reaction time, and stoichiometric ratio by in situ Knudsen-cell mass spectrometry. When combined with fluorofullerene product ratios from larger-scale (bulk) screening reactions with the same reagents, an optimized set of conditions was found that yielded the greatest amount of C 60F 8 (KMnF 4/C 60 mol ratio 28–30, 470 °C, 4–5 h). Two isomers of C 60F 8 were purified by HPLC, one of which has not been previously reported. Quantum chemical calculations at the DFT level combined with 1D and 2D 19F NMR, FTIR, and FT-Raman spectroscopy indicate that the C 60F 8 isomer previously reported to be 1,2,3,8,9,12,15,16-C 60F 8 is actually 1,2,3,6,9,12,15,18-C 60F 8, making it the first high-temperature fluorofullerene with non-contiguous fluorine atoms. The new isomer, which was found to be 1,2,7,8,9,12,13,14-C 60F 8, is predicted to be 5.5 kJ mol −1 more stable than 1,2,3,6,9,12,15,18-C 60F 8 at the DFT level. In addition, new DFT calculations and spectroscopic data indicate that the compound previously isolated from the high-temperature reaction of C 60 and K 2PtF 6 and reported to be 16-CF 3-1,2,3,8,9,12,15-C 60F 7 is actually 18-CF 3-1,2,3,6,8,12,15-C 60F 7.

Jahn—Teller Ordering in Manganese(III) Fluoride Sulfates. Part 2. Phase Transition and Twinning of K2[MnF3(SO4)] and 1D Magnetism in Compounds A2[MnF3(SO4)] (A: K, NH4, Rb, Cs).

AbstractFor Abstract see ChemInform Abstract in Full Text.

Odd magnetic dichroism of linearly polarized light in the antiferromagnet MnF2

The two-sublattice tetragonal antiferromagnetic crystal manganese fluoride is found to exhibit dichroism induced by a magnetic field H∥C4∥Z for linearly polarized light propagating along the tetragonal axis of the crystal also. The observed effect is odd with respect to the sign of the z projection of the field and the operation of reversing the directions of the sublattice magnetic moments of the antiferromagnet. The effect can be used for optical visualization of 180-degree (time-reversed) antiferromagnetic domains in MnF2.

Jahn‐Teller‐Ordnung in Mangan(III)‐fluoridsulfaten. II. Phasenübergang und Verzwillingung bei K2[MnF3(SO4)] und 1D Magnetismus in Verbindungen A2[MnF3(SO4)] (A = K, NH4, Rb, Cs)

AbstractJahn‐Teller Ordering in Manganese(III) Fluoride Sulfates. II. Phase Transition and Twinning of K2[MnF3(SO4)] and 1D Magnetism in Compounds A2[MnF3(SO4)] (A = K, NH4, Rb, Cs)According to single‐crystal X‐ray investigations, K2[MnF3(SO4)] crystallizes at low temperature, like the isostructural Rb, NH4, and Cs analogues in space group P21/c, Z = 4, e.g. at 100 K with a = 7.197, b = 10.704, c = 8.427Å, β = 91.84°. Below about 300 K, the crystals are found to be [001] axis twins. Using a new integration method for area detector records, nearly complete intensity data could be gained allowing for structure refinements of similar quality as for untwinned crystals (e.g. at 100 K: wR2 = 0.050, R = 0.020 for all reflections). With rising temperature, the monoclinic angle approaches continuously 90°. For an ordering parameter Δβ = β−90° a 2nd‐order phase transition is observed with an exponent λ = 0.17. At the transition temperature of 280 K resulting from the fit, the monoclinic structure changes – with delay – to orthorhombic with the minimum super‐group Pnca, a = 7.243, b = 10.763, c = 8.457Å, R = 0.024, as found in an early structure determination at room temperature by Edwards 1971. In the chain‐like [MnF3(SO4)]2− anions, manganese(III) is octahedrally coordinated by two trans‐terminal and two trans‐bridging fluorine ligands as well as by the O atoms of two trans‐bridging sulfate ligands. At low temperature, the octahedral elongation by the Jahn‐Teller effect alternates between a F–Mn–F and an O–Mn–O axis (antiferrodistortive ordering). All bridges are asymmetric. From about 320 K on they become symmetric. Due to 2D dynamical Jahn‐Teller effect all octahedra appear compressed. All compounds A2[MnF3(SO4)] show 1D antiferromagnetism. The antiferrodistortive Jahn‐Teller order at low temperatures and the small bridge angles explain the much lower magnetic exchange energies and their inverse relation to the bridge angles as compared with other fluoromanganate(III) chain compounds with the usual ferrodistortive ordering.

Manganese (III) fluoride as a new synthon in Mn cluster chemistry

Abstract The syntheses and structures of five new Mn3+ clusters [Mn26O17(OH)8(OMe)4F10(Bta)22(MeOH)14(H2O)2] (1), [Mn10O6(OH)2(Bta)8(py)8F8] (2), {NHEt3}2[Mn3O(Bta)6F3] (3), [Mn8O4(OMe)2(Me2Bta)6F8(Me2BtaH)(MeOH)8] (4), and [Mn13O12(Me2Bta)12F6(MeOH)10(H2O)2] (5), are reported, thereby demonstrating the utility of MnF3 as a new synthon in Mn cluster chemistry.

Oxidation of Vicinal Diketones with Manganese(III) Fluoride

AbstractFor Abstract see ChemInform Abstract in Full Text.

Oxidation of vicinal diketones with manganese(III) fluoride

Vicinal diketones were oxidised, at room temperature, to carboxylic acids by manganese(III) fluoride with 90% yield. Investigation of the kinetics suggested that the reaction proceeded via a cyclic intermediate.

Development of a new neutron 4-circle diffractometer and application to the crystal and magnetic structure of MnF 2

We have developed a four-circle diffractometer for a single-crystal sample at the guide-hall of the reactor JRR-3M at JAERI (Japan Atomic Energy Research Institute). We have also developed a horizontally and vertically bent monochromator with silicon crystals. The wavelength of the neutron is 1.57 A, and the maximum scattering angle of the detector is 156°. To evaluate the apparatus, we investigated crystal and magnetic structures of manganese fluoride MnF2. A very good R factor is obtained for structure analysis, and the 3d-electron density, which is carrying spins, is obtained by analyzing the magnetic structure factors. The structure parameters obtained compare well to the reported values, and the imaging of the spin density indicates the powerfulness of the single-crystal neutron experiments.

Radiolysis of [EtC5H4Mn(CO)2NO]+(PF6)– and Evolution of the Nearest Environment of the Manganese Atoms in the Complex

X-ray emission and EXAFS spectroscopies were used to examine changes in the nearest environment of manganese atoms upon radiolysis of [EtC5H4Mn(CO)2NO]+(PF6)– at different energy exposures (Φ). It was found that the initial complex loses the CO and NO ligands at Φ = 4.5 × 106 J/m2. An increase in Φ to ≥7.5 × 106 J/m2 gives rise to Mn–Mn bonds with lengths characteristic of Mn dimers. At Φ = 9.0 × 106 J/m2, Mn nanoparticles are formed; they interact with the carbon atoms of EtC5H4 and the fluorine atoms of PF6 anions. Further increase in Φ = 2.6 × 107 J/m2 yields manganese-containing nanoparticles structured like metallic Mn; their surface atoms interact with carbon atoms formed in the disintegration of the EtC5H4 ligands. The formation of manganese carbides and fluorides at Φ = 2.6 × 108 J/m2 reduces the content of the metal constituent in nanoparticles; this content is zero at Φ = 4.4 × 108 J/m2. The final radiolysis products are manganese carbides and fluorides (or fluorocarbides).

Manganese fluoride epitaxial growth on Si(111)

Epitaxial MnF2 layers were grown on CaF2/Si(111) substrates using molecular beam epitaxy. Layer-by-layer growth was observed at room temperature. The first three molecular layers of MnF2 have cubic fluorite lattice inherited from CaF2. Thicker layers have tetragonal lattice of rutile with (110) plane parallel to the substarte surface and [001] axis along 〈110〉 directions of CaF2. Thus there are three orientations of rotational domains in the MnF2 layer. At a temperature higher than 400°C, nucleation begins with three-dimensional clusters which are aligned with respect to steps on CaF2 surface. After coalescence of the clusters, single domain film can be obtained.

Magnetic Properties and Neutron Diffraction Study of the Chlorofluoride Series Ba2MM′F7Cl (M, M′=Mn, Fe, Co, Ni, Zn)

The magnetic properties of the new chlorofluoride series Ba2MM′F7Cl (M,M′=Mn, Fe, Co, Ni, Zn) have been investigated by susceptibility and magnetization measurements on powder or single-crystal, Mössbauer spectrometry, and neutron diffraction experiments. Our results allow a direct comparison with the magnetic behavior of the well-known series BaMF4(M=Mn, Fe, Co, Ni, Cu, Zn), whose structure is closely related to the chlorofluoride structure. High-temperature series expansion has been used in the case of the manganese and nickel compounds to determine the average magnetic exchange parameter. Mössbauer acquisitions on the Ba2FeMF7Cl series show that, despite the close similarity between the magnetic susceptibilities, hyperfine structure is greatly disturbed by chlorine substitution. The other main difference between both series is the absence of the spin–flop transition observed on the manganese fluoride and in the field-dependent transition observed on the nickel chlorofluoride. Indeed, the field dependence of the magnetization of a Ba2Ni2F7Cl single crystal shows the existence of a magnetic transition when (H) is parallel to (c). The determination of the magnetic structure of Ba2Ni2F7Cl by neutron powder diffraction allows us to propose a qualitative explanation of this transition. We also report the magnetic structure determination in the case of the cobalt compound. In both cases (Ni or Co compounds), the magnetic structures are closely related to those of the corresponding fluorides. The magnetic structure of the mixed compounds Ba2MnNiF7Cl and Ba2FeCoF7Cl are also reported.

The Mixed Anionic Framework in the Structure of Na2{MnF[PO4

In the crystal structure of hydrothermally synthesized sodium manganese fluoride orthophosphate, Na2{MnF[PO4]}, two kind of cis-MnO4F2 octahedra share common vertices to form (Mn2F2O8) chains parallel to the b axis of the monoclinic unit cell. In the a and c directions these chains are linked by PO4 tetrahedra to form a three-dimensional framework of octahedra and tetrahedra. Na+ cations are located in the channels of this framework structure. The problem of {OTX5} mixed anionic radical polymorphism is discussed.

High-pressure structural studies of alkali manganese(III) fluorides

High-pressure structural studies of alkali manganese(III) fluorides

Coercivity of interphase boundaries at magnetization of antiferromagnetic MnF2 in the intermediate state

Magnetic susceptibility of AFM manganese fluoride has been studied at the intermediate state under the spinflop transition. The sample magnetization component related to the irreversible displacement of interphase boundaries is separated experimentally. In particular, at a strict orientation of an external magnetic field along the crystal easy axis magnetic susceptibility of a sample induced by the irreversible displacement of domain walls by the Barkhausen jumps is about 75% of the total susceptibility. Proceeding from specific features of the experimental curves, a method of the exact determination of position of special points on the phase diagram of AFM crystals is proposed.