151Eu Mössbauer Study of Calcium Aluminate Glass and Glass Ceramics Containing a Small Amount of Europium(III)

¹⁵¹Eu Mössbauer spectrum of IR-transmitting calcium aluminate glass, 60CaO·32Al₂O₃·5Fe₂O₃·3Eu₂O₃, consists of a broad peak due to distorted Eu(III) with and values of 0.91 and –2.02 mm·s^–1, respectively. Debye temperatures (_D) of 360 and 320 K were obtained from the temperature dependence of absorption area (A) and that of , respectively. These _D values indicate that Eu(III) atoms occupy substitutional sites of distorted Al(III)O₄ tetrahedra in calcium aluminate glass. The value of 0.62 mm/s obtained from the heat-treated sample (glass ceramic) indicates that Eu(III)-O bonds became less covalent. A smaller value of –1.20 mm·s^–1 was obtained for Eu(III) in the glass ceramic, indicating less distorted Eu(III)O₄ tetrahedra.     

X-Ray Diffraction and 57Fe Mössbauer Study of Iron(II) n-Butylboronate Dichloroglyoximate in a Wide Temperature Interval

The crystal and molecular structure of the clathrochelate complex Fe(Cl₂Gm)₃(BBu ⁿ )₂([tris(-1,2-dichloro-1,2-ethanedionedioximato-O:O")di-n-butyldiboronato-2)-N-N₁,N₂,N₃,N₄,N₅-iron(II)) were solved by X-ray diffraction analysis at 180, 208, 250, and 298 K. A model for the dynamic temperature-dependent disorder of the macrobicyclic ligand was proposed based on an analysis of packing and molecular geometry and on the data of calorimetry and ⁵⁷Fe Mössbauer spectroscopy.     

Analysis of the Probability of the Mössbauer Effect in Iron(III) β-Diketonates

The probability of the Mössbauer effect f has been evaluated and the Debye temperatures of intermolecular vibrations _M at 295 and 78 K have been determined for ten Fe(III) -diketonates, which are complexes of molecular type. Variation of _M with temperature and molecular mass M has been found; in the latter case, _M decreases as M increases. As a result of this antibatic change in _M and M, the effect of a decreased energy of intermolecular interaction dominates the effect of increased molecular mass, and f decreases in conformity with the prediction provided by the molecular crystal model.     

Parameters and Form of the Mössbauer Spectra of Iron(III) β-Diketonates: New Data

Mössbauer spectra have been measured at 295 and 78 K for ten ⁵⁷Fe-enriched iron(III) -diketonates differing in the type of radical in the chelate ring. Since the literature data for compounds of this class are incomplete and contradictory, a repeated analysis of spectrum shape and parameters has been performed. The chemical shift and quadrupole splitting are virtually independent of the type of radical in the chelate ring whereas the line width and asymmetry exhibit a pronounced dependence on the temperature and composition of the compounds. The available concepts on the nature of quadrupole splitting and relaxation mechanisms determining the lineshape for the given compounds are refined. It is concluded that electron spin relaxation is longitudinal or transverse relative to the principal axis of the electric field gradient in different compounds.     

Mössbauer Study of the Structure of Fe - Zircon System

Iron-doped silicate (zircon), prepared by a ceramic method with the addition of LiF as mineralizer, was analyzed by X-ray powder diffraction (XRD) and ⁵⁷Fe Mössbauer spectroscopy to obtain information on the solid solution formation. The results of X-ray diffraction and Mössbauer spectroscopy have shown that only a small fraction of iron, about 1.5 mol%, is incorporated in the zircon structure as paramagnetic Fe³⁺ species while the remaining Fe³⁺ cations form magnetic -Fe₂O₃ particles which are trapped within the zircon matrix.     

Investigation on the magnetic and Mössbauer spectroscopy of 57Fe doped LiMnPO4

Journal of Radioanalytical and Nuclear Chemistry - The 57Fe doped LiMnPO4 cathode with potential applications in Li-ion batteries was prepared by solid-state reaction. The magnetic susceptibility...     

Mössbauer Spectroscopy of Iron Oxides and Related Compounds

The superparamagnetic iron oxide particles with a diameter of about 10 and 16 nm were obtained by the reaction of Fe²⁺ and Fe³⁺ ions in a water pool of reversed microemulsions. The obtained particles were ascribed to -Fe₂O₃ due to the oxidation of Fe₃O₄. Very fine particles of -Fe and Fe₃O₄ were also obtained by the thermal decomposition of FeC₂O₄2H₂O. The decomposition products and their particle size depended on the heat treatments.     

Spectral and physico-chemical investigations of novel homo-dinuclear di-μ2-alkoxo bridged Schiff base complexes: 57Fe Mössbauer parameters of the Fe(III) complex

Spectral and molecular model computations on homo-dinuclear complexes [M₂L₂(H₂O)₂Cl₂] [L = 1-(salicylaldeneamino)-3-hydroxypropane, M = Cr³⁺, Mn³⁺, Fe³⁺, Co³⁺, Ni³⁺ or Cu³⁺] are consistent with a distorted hexa-coordinate geometry. X-band EPR spectral data indicated a rhombic distortion around Cu(II) ion. Magnetic moment and ⁵⁷Fe Mössbauer data confirmed a high-spin state electronic configuration (t_2g³e_g², S = 5/2) and asymmetric ligand environment around Fe(III) with nuclear transitions Fe(±3/2 → 1/2) exhibiting Kramer's double degeneracy. The neighboring Fe(III) nuclei in the homo-dinuclear species are antiferromagnetically coupled.     

Mössbauer and electronic spectral studies of iron(III) complexes of oximes

The hydroxo-bridge complexes of the type [Fe(2)(ligand-H)(4)(OH)(2)] with bidentate nitrogen-oxygen donor ligands, viz. 2-hydroxynaphthaldehydeoxime [hnoH(2)], 2-hydroxyacetphenoneoxime [haoH(2)], salicylaldooxime [SalH(2)], 2-hydroxypropiophenoneoxime [hnoH(2)] have been prepared. All the complexes have been characterized by elemental analysis, magnetic moments, electronic and M?ssbauer spectral studies. M?ssbauer parameters of the complexes clearly suggest high spin configuration of Fe(III) showing lower magnetic moment to that of the spin only value, i.e. 5.92 BM. It may be due to the antiferromagnetic interaction between Fe(III) centers.     

Vibrational and 57Fe-Mössbauer spectra of some mixed cation diphosphates of the type M(II)Fe2(III)(P2O7)2

The infrared (IR), Raman and 57Fe-M?ssbauer spectra of SrFe2(P2O7)2, BaFe2(P2O7)2 and PbFe2(P2O7)2 were recorded and discussed on the basis of the structural peculiarities of the compounds.     

57Fe Mössbauer spectroscopic study of some clusters related to Fe3(CO)12

The ⁵⁷Fe Mössbauer spectra of Fe₃(CO)₁₂-related clusters [Fe₃(CO)₁₁]²⁻, [Fe₂Ru(CO)₁₂], [FeRu₂(CO)₁₂], [Fe₃(CO)₁₁PPh₃], [Fe₃(CO)₁₁PPh₂Me], [Fe₃(CO)₁₁PPhMe₂], [Fe₃(CO)₉(PPh₂Me)₃], [Fe₂Ru(CO)₁₁P(OMe)₃], [FeRu₂(CO)₁₁PPh₃] and [FeRu₂(CO)₁₀(PPh₃)₂] have been recorded at 78 K. The data are compared with published data for other M₃ clusters.Generally, the isomer shifts (δ) fall within a narrow range, for example with compounds containing Fe or Fe and Ru and four or five CO ligands per metal, all δ values lie between 0.29 and 0.36 mm s⁻¹ even though the ligands may be terminal, doubly bridging or triply bridging. Values of quadrupole splitting (Δ) are much more susceptible to changes in the Fe environment, for example the Fe(CO)₄ sites have Δ values from about zero {Fe(CO)₄^t in [Fe₃(CO)₁₂)]} to 1.52 {Fe(CO)₃^tCO^tbr in [Fe₃(CO)₁₁]²⁻}. The quadrupole splitting of the Fe site in [FeRu₂(CO)₁₂] (0.77 mm s⁻¹) clearly indicates that the structure of this cluster is not exactly similar to that of [Ru₃(CO)₁₂]. Substitution of CO by phosphine in general leads to small changes in Δ and Δ if the geometry of the Fe site is unaltered. However, Δ especially can be affected if phosphine substitution cause changes in geometry or if there is multiple substitution.     

Mössbauer,FT-IR,and XRD study on the crystallization of highly functional tungstate and vanadate glasses

⁵⁷Fe-Mössbauer spectra of 38Na₂O·61WO₃·⁵⁷Fe₂O₃ glasses, heat treated at 355°C for 5–150 min, show a change of the coordination number of Fe³⁺ from 6 (FeO₆ octahedra) to 4 (FeO₄ tetrahedra), as a result of the formation of Na₂W₂O₇ (Na₂O/WO₃=1/2), Na₂WO₄ (Na₂O/WO₃=1.0), FeWO₄, and Fe₂WO₆ phases.⁵⁷Fe-Mössbauer spectra of 25K₂O·65V₂O₃·10Fe₂O₃ glasses show a drastic decrease of and after the heat treatment at 340°C for 10–2100 min, since a homogeneous crystallization took place without a phase separation. A KV₃O₈ phase with the K₂O/V₂O₅ ratio of 1/3 was precipitated, and the ratio was equal to the K₂O/(V₂O₅+Fe₂O₃) ratio of the original 25K₂O·65V₂O₃·10Fe₂O₃ glass.     

57Fe Mössbauer spectroscopic and magnetic study of a spin-crossover polymer complex, Fe(3-chloropyridine)2Ni(CN)4

The coordination polymer Fe(3-chloropyridine)₂Ni(CN)₄ (2) has been prepared by a method similar to that for Fe(pyridine)₂Ni(CN)₄ (1). The complex (2) has been characterized by⁵⁷Fe Mössbauer spectroscopy and a SQUID technique.⁵⁷Fe Mössbauer and magnetic susceptibility data show that complex (2) exhibits spin-crossover behavior. The spin transition of (2) occurs between 120 and 80 K with very small hysteresis or without hysteresis. The temperature range of the spin transition in (2) is lower than that in (1). A residual high spin iron(II) fraction is observed at low temperatures in (2), being different from (1). SQUID data also show that samples treated differently yield different spin transition curves.     

Mössbauer study of the thermal decomposition of alkali dihydroxo tetrapropionato ferrates(III)

Thermal decomposition of alkali dihydroxo tetrapropionato ferrates(III), M₃[Fe(C₂H₅COO)₄(OH)₂]xH₂O (M=Li, Na, K) has been studied upto 973 K. The complexes were calcined isothermally at various temperatures i. e., 473, 573, 773 and 973 K. The intermediates/products have been characterized by Mössbauer, infrared spectroscopies and XRD powder diffraction. The anhydrous complexes directly decompose to give -Fe₂O₃ and alkali metal carbonate without undergoing reduction to iron(II) moiety. An increase in the particle size and internal magnetic field of -Fe₂O₃ has been observed with increasing decomposition temperature. At higher temperature (973 K) MFeO₂ is formed as the final thermolysis product due to a solid state reaction between -Fe₂O₃ and alkali metal carbonate.     

57Fe Mössbauer spectroscopic studies of electron-hopping processes in vesuvianites

Room temperature and liquid-nitrogen temperature ⁵⁷Fe Mössbauer spectra of a number of vesuvianite crystals are reported. Certain of the spectra contain doublets whose parameters are intermediate between those normally associated with Fe²⁺ and Fe³⁺ ions in oxide environments. These doublets are attributed to electron-hopping processes between Fe²⁺ ions and adjacent Fe³⁺ or Ti⁴⁺ ion.     

Mössbauer effect study on dispersion and annealing behaviour of Fe(III) ions coprecipitated with neodymium trihydroxide

Mössbauer resonance examination at 300 and 77 K of Fe(III) ions 5 weight percent coprecipitated with neodyminum trihydroxide and heated for 24 hr at 100, 350, 600, 725 and 825°C is reported. To investigate the nature of thermal and microstructural processes which occur during phase transitions, samples annealed at different temperatures from 100 to 1200°C were also studied using thermal analysis, IR spectroscopy, electron microscopy and powder X-ray diffraction. Iron ions exist as very fine ferric oxide hydrate gel like species in the coprecipitate. Removal of water in early stages at 100°C results in strengthening of iron ions while in samples annealed at 350°C a particular loosening of iron sites is observed accompanying disruption of lattice planes due to pronounced dehydroxylation. Annealing to 600°C results in precipitation of NdFeO₃ like microphases in CNd₂O₃ lattice. For samples annealed at 725°C C→ANd₂O₃ transformation takes place and the Mössbauer spectra show a quadrupole split doublet resulting from dispersion of iron microphases. Annealing to 825°C, crystallization to hexagonal ANd₂O₃ takes place. Iron ions held still in defect correlated lattice sites exhibit magnetic ordering due to pronounced agglomeration of NdFeO₃ microphases in ANd₂O₃.     

The structure of Fe(III) ions in strongly alkaline aqueous solutions from EXAFS and Mössbauer spectroscopy

To establish the structure of ferric ions in strongly alkaline (pH > 13) environments, aqueous NaOH solutions supersaturated with respect to Fe(III) and the solid ferric-hydroxo complex salts precipitating from them have been characterized with a variety of experimental techniques. From UV measurements, in solutions of pH > 13, only one kind of Fe(III)-hydroxo complex species was found to be present. The micro crystals obtained from such solutions were proven to be a new, so far unidentified solid phase. M?ssbauer spectra of the quick-frozen solution and that of the complex salt indicated a highly symmetrical ferric environment in both systems From the EXAFS and XANES spectra, the environment of the ferric ion in these solutions (both native and quick-frozen) and in the complex salt was found to be different. In the complex salt, the bond lengths are consistent with an octahedral coordination around the ferric centres. In solution, the coordination geometry of Fe(III) is most probably tetrahedral. Our results demonstrate that in strongly alkaline aqueous solutions, ferric ions behave very similarly to other structurally related tervalent ions, like Al(III) or Ga(III).