Further investigations on the thermophysical properties of gamma-irradiated urania-doped orthoferrites

(Y_1.85?U_0.15) FeO₃ orthoferrite was carefully prepared using the solid-state high temperature ceramic and sintering technique. On this orthoferrite, numerous measurements have been undertaken before and after 1.24 Mrad γ-absorbed dose, namely X-ray diffraction (XRD), DC-electrical conductivity versus temperature, UV/Vis. absorption, IR absorption, Mössbauer effect (ME) and EPR. In the present work the results obtained were explained, interpreted and discussed in details on the basis of lattice structure of the new perovskite investigated and the interaction of γ-radiation with the orthoferrite lattice.     

Concentration Dependence of Mössbauer Parameters of SnCl−3 and SnBr−3 Complex Ions

Mössbauer parameters of frozen salt solutions could be correlated with apparent degree of dissociation, γ. KSnCl₃ and KSnBr₃ were dissolved in 0.5 M H₂SO₄, whereas NH₄ SnCl₃ was dissolved in 0.5 M HClO₄. Mössbauer studies were made at different concentrations.     

Crystal structure and the magnetic properties of tris(2-chloromethyl-4-oxo-4H-pyran-5-olato-κ2O5,O4)iron(III)

The tris(2-chloromethyl-4-oxo-4H-pyran-5-olato-κ²O⁵,O⁴)iron(III), [Fe(kaCl)₃], has been synthesized and characterized by the crystal structure analysis, magnetic susceptibility measurements, Mössbauer, and EPR spectroscopic methods. The X-ray single crystal analysis of [Fe(kaCl)₃] revealed a mer isomer. The magnetic susceptibility measurements indicated the paramagnetic character in the temperature range of 2 K–298 K. The EPR and Mössbauer spectroscopy confirmed the presence of an iron center in a high-spin state. Additionally, the temperature-independent Mössbauer magnetic hyperfine interactions were observed down to 77 K. These interactions may result from spin–spin relaxation due to the interionic Fe³⁺ distances of 7.386 Å.     

Magnetic Properties of M3[Fe(Cn)6]2Xh2O (M = Co (II), Ni(II), Cu(II), Zn(II))

Compounds of the type M₃[Fe(CN)₆]₂XH₂O (M = Co(II), Ni(II), Cu(II), and Zn(II)) were prepared and magnetic properties of their powders were investigated by means of EPR spectra, Mössbauer effect and magnetic susceptibility measurements. The temperature dependence of the magnetization for the complexes Co₃[Fe(CN)₅]₂- 10H₂O, Ni₃[Fe(CN)₆]₂-10H₂O and Cu₃[Fe(CN)₆]₂-4H₂O revealed that below the critical temperatures 15, 22 and 20 K respectively, these complexes have zero-field magnetization. The magnetic hysteresis at 10 K for Co(II), Ni(II) and Cu(II) complexes was observed. Mössbauer spectra at 4.2 K for the compounds are discussed.     

Crystal structure and magnetic properties of tris(2-hydroxymethyl-4-oxo-4H-pyran- 5-olato-κ2O5,O4)iron(III)

Tris(2-hydroxymethyl-4-oxo-4H-pyran-5-olato-κ²O⁵,O⁴)iron(III) [Fe(ka)₃], has been characterised by magnetic susceptibility measurements Mössbauer and EPR spectroscopy. The crystal structure of [Fe(ka)₃] has been determined by powder X-ray diffraction analysis. Magnetic susceptibility and EPR measurements indicated a paramagnetic high-spin iron centre. Mössbauer spectra revealed the presence of magnetic hyperfine interactions that are temperature-independent down to 4.2?K. The interionic Fe³⁺ distance of 7.31?Å suggests spin-spin relaxation as the origin of these interactions.     

Mössbauer Spectroscopic Studies of Supported α-Fe2O3 and Fe Catalysts II: The Effect of the Second Metal Addition

The effect of the addition of a second metals such as Zn and Ni on the calcinaton and reduction of alumina, magnesia and silicasupported iron catalysis with total iron loading of 5wt% is investigated by Mössbauer spectroscopy. It is shown that the reducibility of supported α-Fe₂O₃ is gradually increased by adding the second metal. The values of the magnetic hyperfine field obtained from Mössbauer spectra for the Zn or Ni-added α-Fe₂O₃ or Fe catalysts decreased with increasing second metal loading.     

Mössbauer study of the corrosion products of iron

Investigations of the possible use of Mössbauer measurements for the analysis of the corrosion products of iron are reported. The Mössbauer spectrum was measured at room and liquid nitrogen temperatures on two samples produced by different corrosion procedures. The isomeric shift, quadrupole splitting and magnetic splitting observed in the spectra yield information on the chemical composition. In this way, the chemical forms of the compounds in the samples could be established. The magnetic properties, revealed by the spectra taken at different temperatures, permitted the identification of the polymorphous modifications. The rust produced in air saturated with water vapour was found to consist of 50% (w/w) Fe₂O₃,～40% γ-FeOOH, and ～10% β-FeOOH, while the rust produced by periodical immersion in saturated calcium chloride solution is composed of about equal amounts of β-FeOOH and γ-FeOOH. These findings have been confirmed by the thermoanalytical curves of the samples. The Mössbauer effect presents a convenient method for the investigation of the corrosion products of iron.     

Radiation durability of aluminophosphate glass prepared for the stable storage of high-level nuclear wastes

⁵⁷Fe Mössbauer spectra of 30CaO·15Al₂O₃·5Fe₂O₃·25PbO·25P₂O₅ glass consist of two quadrupole doublets due to distorted Fe(III)O₆ and Fe(II)O₆ octahedra. Mössbauer spectra of the aluminophosphate glass irradiated with⁶⁰Co γ-rays (≈5·10⁴Gy) were essentially the same as those of non-irradiated glass. Mössbauer spectra of γ-ray irradiated aluminophosphate glass, containing 10 stable isotopes (Sr, Y, Zr, Nb, Mo, Ba, La, Ce, Pr, and Nd) as the simulated nuclear waste, were also the same as those of non-irradiated glass. These results indicate that the aluminophosphate glass containing iron and lead has high radiation-durability, in addition to high heat resistivity and high water resistivity.     

Surface study of the corrosion of carbon steel in solutions of ammonium salts using Mössbauer spectrometry

The effect of the NO_3? anion on the corrosion of carbon steel in a solution of 0.1M NH₄Cl (pH 5.5) was studied by galvanostatic polarization and Mössbauer spectrometry. The anion has an inhibiting effect by decreasing the expansion rate of generalized corrosion of carbon steel in a solution of 0.1M NH₄Cl. Mössbauer spectroscopy shows that a superficial compound is formed on the electrode surface as a result of corrosion, presenting no magnetic ordering. Its parameters show the initial stage of corrosion. We assume that at this stage the main corrosion product is a mixture of ferrihydrite Fe(III) and FeOOH (α and/or γ).     

Detecting unalloyed tin in LiSn2(PO4)3-based anodes with Mössbauer spectroscopy

The first discharge of the Li⁺ ion anode material LiSn₂(PO₄)₃ was investigated with Mössbauer spectroscopy and electrochemical techniques. Mössbauer spectroscopy provided insight into the structure of the tin atoms of the fully discharged anode materials. Spectra consist of overlapping peaks, which are assigned to noncrystalline β-Sn and Li–Sn alloy domains. An analysis of the relative intensities of the Mössbauer spectra shows the relative abundance of β-Sn increases at the expense of the Li–Sn alloy as the discharge rate increases. Cell polarization occurs at higher discharge rates, leading to inefficient electrode utilization and poor cycling performance. Sluggish Li⁺ ion diffusion through the amorphous Li₃PO₄ network that is formed early in the discharge process might be responsible for the poor electrochemical performance and the accumulation of unalloyed tin.     

Mössbauer-Messungen an Sn2O3

Mössbauer Studies on Sn₂O₃ Mössbauer data for ¹¹⁹Sn in Sn₂O₃ show this compound to contain bivalent and tetravalent tin. Whereas tin(IV) is coordinated in a similar way in Sn₂O₃ and SnO₂, a rather large quadrupole splitting indicates an environment of low symmetry for tin(II).     

In situ — High Temperature Mössbauer Spectroscopy of Iron Nitrides and Nitridoferrates

The stoichiometric iron nitrides γ′‐Fe₄N, ε‐Fe₃N and ζ‐Fe₂N were characterized by Mössbauer spectroscopy. The thermal decomposition of ε‐Fe₃N was studied in‐situ by means of a specially developed Mössbauer furnace. We found ε‐Fe₃N to γ′‐Fe₄N and ε‐Fe₃N_x (x ≥ 1.3) as decomposition products and determined the border of γ′/ε transformation at T ? 930 K. Mössbauer spectroscopy was applied to study in‐situ the thermal decomposition of the nitridometalate Li₃[Fe^IIIN₂] and the formation of Li₂[(Li_1‐xFe^I_x)N], the compound with the largest local magnetic field ever observed in an iron containing material. The kinetics of formation and the stability of Li₂[(Li_1‐xFe^I_x)N] was of particular interest in the present study.     

Structural studies of magnetic nanoparticles doped with rare-earth elements

Magnetic nanoparticles and those doped with rare-earth metal ions having spinel structure were synthesized, possessing the average particles size of 11.3-13.4 nm. According to Mössbauer spectroscopy data it can be concluded that prepared iron oxide nanoparticles are γ-Fe₂O₃. For materials containing rare-earth elements the decrease of octahedral component surface was observed in comparison to non-doped material, what can be explained by Eu³⁺, Sm³⁺ и Gd³⁺ ions occupying the octahedral position.     

Cation distribution and related properties of MnxZn1−xFe2O4 spinel nanoparticles

Mn_xZn_1−xFe₂O₄ (x = 0.05…0.9) nanoparticles prepared via sol–gel hydrothermal process were investigated by X-ray powder diffractometry (XRPD), transmission electron microscopy (TEM), ⁵⁷Fe Mössbauer spectroscopy (MS), electron paramagnetic resonance spectroscopy (EPR), X-ray absorption near edge structure spectroscopy (XANES) and magnetic hysteresis measurements. XRPD measurements revealed a non-monotonic dependence of the cubic lattice parameter on the Mn concentration, which is interpreted as being the result of a corresponding variation in the inversion degree (concentration of Fe ions on the occupied tetrahedral lattice sites) of the studied spinels. XANES measurements indicated that the average oxidation state of Mn ions decreases with the applied Mn concentration, in contrast with Fe ions that were found to be exclusively in the 3+ oxidation state by MS measurements. EPR spectra recorded as a function of temperature enabled the determination of the characteristic anisotropy energy barrier of the superparamagnetic particles, and contributed to the clarification of peculiarities of the corresponding ⁵⁷Fe Mössbauer spectra. On the basis of the observed results the interdependences among the sample stoichiometry, the cubic cell parameter, the particle size, the inversion degree, the magnetic ordering temperature and the effective magnetic anisotropy are discussed.     

121Sb-Mössbauer-Spektren von Antimon(V)-Verbindungen. II

¹²¹Sb Mössbauer Spectra of Antimony (V) Compounds. II The Mössbauer resonance effect of ¹²¹Sb has been studied at 4.2 K in a series of 11 antimony(V) compounds which are in most cases bridged. Isomer shift and quadrupole splitting variations are considered in the light of results of X-ray and vibrational spectroscopy. Preparation and the vibrational spectra of [NMe₄][SbCl₄(n₃)₂] are described. Within the limitations of available structural data related tin compounds are compared with those of corresponding ¹¹⁹Sn Mössbauer spectra.     

Mössbauer resonance study of the 6H-Type BaFeO2.72

The BaFeO_3?y phase, the structure of which is related to the 6H-type hexagonal perovskite, has been investigated for y = 0.28 using in particular Mössbauer spectroscopy. An X-ray diffraction analysis of BaFeO_2.72 reveals a quite similar pattern to that of the stoichiometric 6H-BaTiO₃, but Mössbauer resonance data show the oxygen vacancies to result likely in the formation of distorted pyramidal sites containing high spin iron (IV).     

Mössbauer and thermogravimetric study of ferrous gluconate

Ferrous gluconate Fe(C₆H₁₁O₇)₂·2H₂O was investigated by means of⁵⁷Fe (14.4 keV)-Mössbauer spectroscopy and thermogravimetry. The Mössbauer study was performed in the temperature range 80 to 423 K. It was found that Fe²⁺ occupies two distinctly different Mössbauer sites in the hydrated phase and a single site in the product of the thermal treatment. All samples were contaminated by some amount of Fe³⁺. A significant oxidation occurs during thermal treatment (about 378 K) at least for the samples exposed to the air. No Goldanskii-Karyagin effect has been detected, in contrast to the previous claim. It has to be noted that the ferrous gluconate is often used as the iron containing component of drugs used in the treatment of anaemia.     

A simple solution route to control synthesis of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanomaterials at low temperature and their magnetic properties

A series of nanostructured iron compounds including cubic Fe₃O₄ and orthorhombic FeOOH were synthesized via a facile low temperature (in the range of 60?100°C) solution method. In the whole process, the interaction between FeCl₂·4H₂O and methenamine (C₆H₁₂N₄) was carried out through a reflux device under different reaction conditions such as temperature, solvent, and duration. The samples were detected by XRD, TEM, SAED, physical property measurement system, and Mössbauer spectroscopy, separately. The experiments showed that magnetic mixture nanoparticles had flake and rod morphologies, and cubic Fe₃O₄ took on grain nanostructure. Magnetism measurements indicated that the saturated magnetization of the as-obtained magnetic mixture was lower than that of the cubic magnetite. Mössbauer spectroscopy testified the sample consisting of cubic magnetite rather than γ-Fe₂O₃. In addition, a possible growth mechanism of cubic magnetic nanoparticles under different conditions was discussed.     

The synthesis and characterization of Dy doped into the perovskite BaCeO3

Concentrations of up to 20 mol.% Dy have been substituted for tetravalent cerium in the perovskite BaCeO₃. ¹⁶¹Dy Mössbauer spectroscopy demonstrates that the dysprosium in this host is present in the trivalent oxidation state. Effective magnetic moments obtained on the same samples confirm these findings. Line broadening as a function of dysprosium concentration, observed from both X-ray and Mössbauer measurements, is attributed to the presence of lattice defects (oxygen vacancies) which are necessary for charge compensation.     

Studies on phases from the M:Sn(II):I:F systems (M =Na,K, Rb,and NH4)

The products obtained from molten and aqueous SnF₂:MI systems (M = Na, K, Rb, and NH₄) have been studied. The Mössbauer data for phases with 1:1, 2:1, and 3:1 SnF₂:MI molar ratios are reported. The MSnIF₂ phases show evidence of two tin sites, one of which has Mössbauer parameters attributable to an octahedral tin(II) environment. The materials obtained are all colored and the reasons for these colors are discussed.