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Abstract
The CO2 absorption properties and the microstructure of (Ba,Ca)(Fe,Mg)O3
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have been studied by TGA, XRD, and Mössbauer spectrometry. Paramagnetic doublets of FeIV and FeIII appeared in the Mössbauer spectra of cubic (Ba0.5Ca0.5)(Fe0.5Mg0.5)O3
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heated in CO2 up to 600 °C, and a pair of sextets of tetrahedral FeIII (Hin = 43 T) and octahedral FeIII (Hin = 51 T) were produced above 800 °C, and an additional sextet characteristic of FeIII in a spinel structure (Hin = 48 T) was observed at 1000 °C. On the other hand, a pair of sextets of tetrahedral and octahedral FeIII of the orthorhombic (Ca0.95Ba0.05)(Fe0.5Mg0.5)O3
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showed hardly any change after absorption of CO2. It is concluded that only a small portion of Mg entered the orthorhombic phase of (Ca0.95Ba0.05)(Fe,Mg)O3
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and Mg preferred the octahedral B site of the perovskite lattice. The excess Mg formed separate CaO-MgO mixed oxide, and the primary mechanism of CO2-trapping is the formation of CaMg(CO3)2.
Abstract
Two bisphenol-A type epoxy resins were irradiated by electron beam and studied afterwards by positron lifetime spectroscopy. An interesting result is that despite the considerable amount of free-radicals no inhibition of positronium formation was observed in the two epoxies. Nevertheless several serious differences were detected between the studied polymers. The results suggest that the radiation-resistant properties of epoxies depend strongly on the amount of the curing agent.
Abstract
151Eu,119Sn and57Fe Mössbauer spectroscopy was used to study high Tc superconductors. Mössbauer spectra of Sn substituted EuBa2Cu3O7–y, YBa2Cu3O7–y and TlBaCaCuO4.5+y as well as of Fe Substituted TlBaCaCuO4.5+y were compared. The Sn and Fe ions replace the regular Cu positions in the YBa2Cu3O7–y and in TlBaCaCuO4.5+y materials, fespectively, while the localization of tin atoms in both the119Sn doped EuBa2Cu3O7–y and TlBaCaCuO4.5+y superconductors is different from that of previous cases. Up to our knowledge, this is the first publication on a Mössbauer study of a Tl-containing superconductor.
Abstract
Mössbauer spectroscopy was used to study phlogopites from ultramafic xenoliths derived from alkali mafic rocks of the Transdanubian Midmountains. On the basis of evaluation of the Mössbauer spectra the following iron sites were identified /using the nomenclature published by Dyar1/ in the samples:
Abstract
57Fe Mössbauer spectroscopy was used to study57Fe doped high Tc TlBaCaCuO4.5+y superconductor between 70 and 295 K. Significant anomalous changes in the shape of the Mössbauer spectrum were observed around the Tc /105–120 K/. This experimental fact could be reproduced. Our finding can be associated with structural changes taking place around the Tc in TlBaCaCuO4.5+y superconductor.
Abstract
Mössbauer spectroscopy and X-ray diffractometry have been used to study Sm–Fe mixed oxides (with different Sm
Fe atomic ratios) annealed at 550, 850, 1000 and 1250 °C. The room temperature Mössbauer spectra can be interpreted in terms of one, two or three sextets and in some cases by an additional doublet depending on the composition and the heat treatment. The sextets have been associated with SmFeO3 perovskite, Sm3Fe5O12 garnet and 
-Fe2O3 hematite. These results are in agreement with those of X-ray diffractometric measurements, which give a clear, evidence of the presence of these phases.
Abstract
Dibenzyltin(IV) complexes of carbohydrate derivatives were prepared and studied by Mössbauer and FTIR spectroscopy and by thermogravimetry. The Mössbauer studies indicated that the reaction between dibenzyltin(IV)-dichloride and sugar-type ligands led to reaction products containing tin(IV)-oxide. beside the dibenzyltin(IV) sugar complex. These two type of species were shown to be in weak interaction. Comparison of the experimental quadrupole splitting values with those calculated on the basis of the partial quadrupole splitting concept revealed the steric arrangements of the coordination sphere of tin(IV) in the sugar complexes.
Abstract
Triphenyltin(IV) complexes ofN-acetylglycine,N-acetyl-L-leucine,N-acetyl-L-asparagine andN-acetyl-L-tyrosine were prepared by two methods and characterized by means of different spectroscopic methods (FTIR, multinuclear,1H,13C and119Sn NMR and119Sn Mössbauer). The spectroscopic data indicated that theN-acetylglycine complex adopts a trigonal-bipyramidal structure in which the monodentate carboxylate and the amide-C=O group are bound to the same organotin(IV) moiety. The other three complexes are linear oligomers in which the planar Ph3Sn(IV) is coordinated axially by a monodentate carboxylate and an amide-C=O from two different ligands. At theC-terminal end of the oligomer chain there is a tetracoordinated tin(IV) with a monodentate carboxylate as donor group.
Abstract
The complexes [Zn(1-propyltetraole)6](BF4)2 (Zn-ptz) and [Fe(methyltetrazole)6](BF4)2 (Fe-mtz) were investigated by positron annihilation and solid-state NMR spectroscopy. For Zn-ptz signs of structural rearrangements were found between 70 and 145 K. For the spin-crossover complex Fe-mtz a transition affecting the high-spin stat Fe2+ ions at lattice site B occurs below 15 K.
