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Abstract
57Fe Conversion electron Mössbauer spectroscopy, X-ray diffractometry and electron microprobe measurements were performed on Fe–Ni–Cr alloys coatings electrochemically deposited at different times (from 1 to 29 minutes). Significant differences have been found among the Mössbauer spectra of samples examined. The changes are also reflected by the hyperfine field distribution derived from the spectra. The observed changes can be associated with changes in the magnetic anisotropy and in the short range ordering in correlated to the duration of electrochemical deposition.
Abstract
Positron lifetime spectroscopic and Dopplerbroadening measurements have been carried out on trans-stilbene single crystals. The results (including the complementary DSC measurement) give new evidence for the existence of phase transitions in trans-stilbene at temperatures between 20 and 300 K.
Abstract
Al–Fe–Mn alloys containing 0.5 wt. % iron and 0–3.0 wt. % manganese were prepared at different cooling rates from 0.1 to 500 K/s and studied by Mössbauer spectroscopy. Beyond the usual phase analysis, it was found that the presence of manganese is responsible for the decrease of the quadrupole splitting and isomer shift of the Al6(Fe,Mn) phase, compared to those of Al6Fe. It was also shown that the Mössbauer parameters are characteristic of the average manganese content of Al6(Fe,Mn) only if there are no substantial fluctuations of the Fe/Mn ratio in the Al6(Fe,Mn) phase. Accurate Mössbauer parameters for the Al6Fe phase were also determined.
Abstract
151Eu and 141Pr Mössbauer spectroscopy was applied to study the effects of Pr substitution for Eu or Ba atoms in Eu1-x
Pr
x
Ba2Cu3O7-
and EuBa2-x
Pr
x
Cu3O7-
, respectively. It was found that there exists a correlation between the 151Eu isomer shift and the onset temperature of the superconducting transition, independent of the location of Pr. This shows that the extra electrons provided by the Pr increase the electronic density in the copper oxide planes and in the 4f orbitals of Eu31, simultaneously. The polycrystalline compound EuBa1.3Pr0.7Cu3O7-
has been investigated by 141Pr Mössbauer spectroscopy. The observed 141Pr isomer shift, (4.2 K) = 0.10(15) mm/s relative to PrF3, reflects a valence state of 3+ for the Pr located at the Ba site in EuBa1.3Pr0.7Cu3O7-
, being in contrast to the valence state of 3.4+ found earlier for Pr which was situated at the rare earth site. This means that the valence state of Pr substituted for Eu is different from that of Pr substituted for Ba. These results suggest that the suppression of superconductivity by Pr substituted for the rare earth atoms is a consequence of the hole filling effect.
Abstract
57Fe Mössbauer spectroscopy measurements were performed on the perovskite compounds Eu0.7Pr0.3Ba2(Cu0.99
57Fe0.01)3O7-
, EuBa1.5Pr0.5(Cu0.99
57Fe0.01)3O7-
and EuBa1.3Pr0.7(Cu0.99
57Fe0.01)3O7-
. The observed 57Fe Mössbauer spectra provided an evidence for the correct site assignment of subspectra originating from 57Fe in different microenvironments. Apart from a minor component which was assigned to the 57Fe in the Cu(2) site of the copper oxide plane, all the subspectra could be attributed to the 57Fe in the Cu(1) copper oxide chain site with a fourfold (doublet D1), fivefold (doublet D2) or sixfold (doublet D3) oxygen coordination. In contrast, in the compound EuBa2(Cu0.99
57Fe0.01)3O7-
the 6-coordinated (D3) species has not been observed. The substitution of Pr for Eu or for Ba resulted in an increased occupancy of the O(5) antichain oxygen sites, which was explained by the charge neutrality criterion. Especially, the replacement of Ba2+ with Pr3+ led to an unusually high degree of occupancy of O(5) sites. In the 57Fe Mössbauer spectra the relative area of the 6-coordinated species (D3) increased, and that of the 4-coordinated one (D1) vanished completely in the case when Pr was substituted for Ba. Furthermore, the proportion of the 6-coordinated (D3) species increased at the expense of the 5-coordinated (D2) one with an increasing concentration of Pr at the Ba site. These experimental results are consistent with the variety of Mössbauer results reported so far.
Abstract
Mössbauer, FTIR and XRD analyses showed that in aqueous medium in air in the presence of L-tryptophan (Trp) or indole-3-acetic acid (IAA) the ambient-temperature ageing of the precipitates formed from ferrous sulphate at pH
7 gave composite phases with varying proportions of 
-FeOOH (a dominating crystalline phase), 
-FeOOH (both fine-grained, showing superparamagnetic behaviour at 298 K, and relatively better crystallized) and amorphous ferric hydroxide. The experimental data suggested a competition for adsorption sites at the oxyhydroxide surface in the suspension during phase transformations, as well as the transformation of -FeOOH (and/or amorphous ferric hydroxide) to -FeOOH via the dissolution-reprecipitation mechanism. The formation of certain ferric oxyhydroxide phases in the presence of Trp and IAA — released e.g., in the course of bacterial and plant metabolism — can contribute to the regulation of soil mineral composition.
Abstract
Multinomial distribution is presented as the most likely distribution of the stoichiometric composition of stochastically formednmers. The termnmer is used in a wide sense, meaning not only the usual species in polymer chemistry, but molecules or a well defined set of neighbouring atoms in a crystal lattice as well. As a practical example the authors present the statistical interpretation of the Mössbauer spectra of ferromagnetic FeCrNi alloys. The problem discussed may also serve as a model calculation for courses on statistical thermodynamics.
Abstract
Electrochemical measurements and Mössbauer spectroscopy were used to study a rapidly quenched Ni80 57Fe1P19 amorphous alloy solution treated between 920 and 1500 °C. Different short range orderings were shown in amorphous alloys solution treated at different temperatures. This finding can be associated with phase separation occurring in the liquid state. This phase separation can be inherited in slightly relaxed amorphous state.
Abstract
Nine complexes of adenosine and related compounds (adenosine-5'-monophosphate, adenosine-5'-triphosphate, 1-methyl-adenosine, pyridoxal-5-phosphate and 
-nicotinamide-adenine-dinucleotide-phosphoric acid) with di-n-butyltin(IV) oxide and/or di-n-butytin(IV) dichloride were prepared in the solid state. The compositions of the complexes were determined by standard analytical methods. It was found that the complexes contain organotin(IV) moiety and the ligand in a ratio of 1:1 or 2:1. The FTIR spectra demonstrated that di-n-butyltin(IV) oxide reacts with the D-ribose moiety of the ligands, while di-n-butyltin(IV) dichloride is co-ordinated to the deprotonated phosphate group. The basic part of the ligands does not participate directly in complex formation. Comparison of the experimental Mössbauer QS values with those calculated on the basis of the PQS concept revealed that the organotin(IV) moiety has trigonal-bipyramidal, octahedral and in some cases tetrahedral geometry also. Some of the complexes contain the organotin(IV) cation in two different surroundings.
