A. Vértes

User-friendly software for Mössbauer spectrum analysis

A new user-friendly software for analysis of Mössbauer-spectra has been developed. The program makes use of the advantages provided by the current generation of fast personal computers. An Evolution Algorithm1,2 is used for global search of Mössbauer parameters in order to enhance the reliability of the obtained results. Fitting of Lorentzians, Pseudo-Voigt line profiles, and deriving hyperfine-field distributions including correlations and combinations and Mössbauer Line Sharpening by Fourier transformation provide a wide range of applicability.

Mössbauer spectroscopy studies of Sn-Pt/Al2O3 catalysts prepared by controlled surface reactions

Abstract Mossbauer spectroscopy was used to study the chemical state of tin in a new type of Sn-Pt/Al2O3 catalysts. Controlled surface reaction of tin tetraethyl with hydrogen preadsorbed on platinum resulted in the exclusive formation of a Pt-SnEt3 surface complex, which decomposed in hydrogen at 773 K to PtxSn alloy (3

Emission Mössbauer Studies of Anodically Formed CoO2

was formed by anodic treatment of deposited on a platinum electrode in a borate buffer at +600–+900 mV (vs. SCE). Anodic polarization of a cobalt electrode at +900 mV yielded a mixture of and . Exposure of to air for 3 months resulted in decomposition to .

Local environments of iron and cobalt in doped MgB2 superconductors

MgB2 has been doped with 57Fe and 57Co in order to probe the electronic structure of the superconductor by Mossbauer spectroscopy. Simultaneous SEM–EDX studies showed that both Fe and Co were incorporated to some extent into the MgB2 host lattice. Mossbauer spectroscopy indicated that Fe2B and FeB were also formed during the preparation. At higher Fe contents Fe2B appeared unambiguously as a secondary phase in the x-ray diffraction. CoB was detected at substitution levels of 10 mol% and greater. Both Fe and Co doping decreased the Tc(0) modestly. Co and Fe were found to substitute at the Mg site in the MgB2 lattice. The Mossbauer parameters for 57Co and 57Fe were consistent with a metallic environment. The similarity of the isomer shifts in MgB2 and in cuprate superconductors is being discussed.

In-situ radiotracer studies of sorption processes in solutions containing (bi)sulfite ions. I. Polycrystalline gold

Abstract In this work, we report some new findings obtained by the in-situ radiotracer and voltammetric studies of the time, potential and pH dependence of sorption processes on polycrystalline gold in ClO 4 − supporting electrolytes containing aqueous SO 2 . Besides this, adsorption behaviour of species created from aqueous SO 2 ( HSO 3 − SO 3 2− ions and/or molecular SO 2 as well as their oxidation and reduction products) is compared with that of HSO 4 − SO 4 2− ions in order to get a deeper insight into the nature and sorption properties of oxidation products. Both the oxidation and reduction of aqueous SO 2 occur on a polycrystalline gold in acid solutions between the onset of hydrogen and oxygen evolution. At higher pH values (3.5 and 6.5) the onset of the oxidation processes shifts towards more positive potentials and the electroreduction commences at less positive potential values. It is probable that a poisoning effect owing to oxidized adspecies rather than the electrocatalytic behaviour of adsorbed reduction products prevail over the electrooxidation phenomena. Both HSO 4 − SO 4 2− and S 2 O 6 2− are presumably formed (and adsorbed) on gold upon electrooxidation of aqueous SO 2 . The apparent inhibition of the electrooxidation processes in acid solutions may most likely be due to the formation of some surface complexes consisting of oxidized adspecies and “strongly bonded” molecular SO 2 .

Mössbauer and X-ray study of rapidly quenched and mechanically alloyed Al-Fe alloys

Mössbauer spectroscopy and X-ray diffractometry were used to study the effect of the cooling rate as well as of the milling time on the structure of rapidly quenched Al-6.8% Fe, Al-0.5% Fe and mechanically alloyed Al-8% Fe alloys. The main phase of the rapidly quenched alloys was identified as AlmFe besides Al6Fe andAlFe solid solutions. In the mechanically alloyed samples (with milling time between 1.5–43 hours), we have found α-Fe, AlFe solid solution and a third phase characterized by a doublet with Mössbauer parameters which are not so far from those of clusters inAlFe alloys. We have observed a continuous increase of the quantity ofAlFe solid solution, together with a significantly less increase of the third phase as a function of the milling time. Simultaneously, the quantity of alpha-iron has gradually decreased.

Metastability in EuBa/sub 2/(Cu/sub 1-//sub x/Sn/sub x/)/sub 3/O/sub 7-y/ studied by /sup 119/Sn and /sup 151/Eu Moessbauer spectroscopy

The metallic oxide compound system EuBa/sub 2/(Cu/sub 1-//sub x/Sn/sub x/)/sub 3/O/sub 7-y/ (x = 0.05, 0.10, 0.20) was prepared for investigation with /sup 151/Eu and /sup 119/Sn Moessbauer spectroscopy. The best fits of the /sup 119/Sn Moessbauer lines reveal at least two different Sn/sup IV/ sites. The /sup 151/Eu spectra are characteristic for Eu/sup III/ state in these compounds. We have found a considerable difference between the shapes of /sup 119/Sn Moessbauer spectra recorded at room temperature and those recorded at the temperature of liquid nitrogen in the case of the sample having the highest tin content. Nevertheless, there is no evidence that this difference has a direct connection with the superconducting behavior.

Mössbauer study of electrodeposited Fe−Cr−Ni alloys

Mössbauer spectroscopy was used to compare Fe−Cr−Ni alloys prepared by different electrochemical as well as thermal methods. The main phase of the electrodeposits was ferromagnetic contrary to the thermally prepared alloys of same composition, which were paramagnetic. Obvious differences can be observed among the spectra of electrodeposited samples of different composition. Narrower line width and smaller paramagnetic contribution can be observed in samples electrodeposited onto A1 substrate compared to those in samples plated onto graphite with modified electrochemical parameters. Changes in hyperfine field distribution of as-deposited and aged samples indicate a precipitation process due to the heat treatment.

Mössbauer and FTIR spectroscopic studies of iron anthranilates: coordination, structure and some ecological aspects of iron complexation

Abstract The data on the coordination and structure of iron(II) and iron(III) anthranilates in the solid state and in aqueous medium are presented and discussed, as studied using Mossbauer (for solid products and frozen solutions) and FTIR spectroscopy (for solid samples). Whereas, in slightly acidic nitrate solutions under aerobic conditions ferric ions can still be gradually reduced by anthranilic ( o -aminobenzoic) acid, which may have some ecological significance, in circumneutral media this process is retarded. Mossbauer parameters calculated for iron(II) and iron(III) anthranilates, as well as characteristic vibration modes of certain functional groups involved in coordination with iron cations are discussed. The FTIR data obtained for ferrous anthranilates, as compared to anthranilic acid, definitely exhibit the direct involvement of both the carboxylic and the amino groups of anthranilic acid in coordination with iron.

Geological and Mineralogical Applications of Mössbauer Spectroscopy

Mossbauer spectroscopy is a useful analytical tool in earth sciences. It is applicable to elements having Mossbauer-active isotopes like iron, tin and gold, etc. It gives information about the oxidation and magnetic state of these elements and about the short-range crystal chemistry of crystalline and amorphous materials containing Mossbauer active nuclides.