Comparative mössbauer and TDPAC studies on the after-effects of the ec decays of119Sb and111In in α-Fe2O3

Mössbauer emission spectra of (¹¹⁹Sb→)¹¹⁹Sn and TDPAC spectra of (¹¹¹In→)¹¹¹Cd in α-Fe₂O₃ are measured. The origin of apparetly much pronouced after-effects of the EC decay observed in the TDPAC spectra, as compared with those in the Mössbauer spectra is clarified.     

119Sn Mössbauer spectroscopy: a powerful tool to unfold the reaction mechanism in advanced electrodes for lithium-ion batteries

Cobalt–tin intermetallic compounds with different particle size have been obtained and characterized by using ¹¹⁹Sn Mössbauer spectroscopy as a main tool. The electrochemical behavior of the Co–Sn compounds has been evaluated in lithium test cells. The Lamb–Mössbauer factors for CoSn with different crystallite sizes have been calculated. The results f _nano???CoSn(300 K) = 0.19 and f _{coarse???CoSn}(300 K) = 0.55 are obtained. Nano-CoSn exhibits larger capacity to react with lithium than coarse-CoSn.     

Internal oxidation of sp-Impurities in silver studied by119Sn Mössbauer spectroscopy

The internal oxidation of the ion-implanted radioactive precursors¹¹⁹Cd and¹¹⁹Sb to the Mössbauer isotope¹¹⁹Sn in silver has been investigated. The oxidation is monitored by the intensity of a line in the Mössbauer spectra, which is characteristic of SnO₂ (δ=(0–0.23)mm/s relative to CaSnO₃, ΔEQ ≈ 0.5 mm/s, ? ≈ 220 K). This line is attributed to an internal oxidation of the implanted impurities by interstitially diffusing oxygen pairs. The formation and annealing kinetics of the impurity-oxygen complexes are interpreted in terms of the diffusion coefficients of oxygen and the sp-impurities in silver, respectively, and the reactivity between them. Comparison is made to Mössbauer experiments on SnAg alloys and to PAC measurements on¹¹¹cd in silver.     

Local environment of Te in GaTe and Ga2Te3 studied with119Sn and129I Mössbauer spectroscopy

The compounds GaTe and Ga₂Te₃ have been studied with Mössbauer source spectroscopy, using the decays^119mTe→¹¹⁹Sb→¹¹⁹Sn and^129mTe→¹²⁹I. For Ga₂Te₃, which has a defect zincblende structure, the spectra give satisfactory fits using two components with intensity ratio roughly 2∶1, in agreement with the two crystallographic sites in this compound. The Mössbauer spectra of GaTe are not easily understood in terms of the three inequivalent Te sites present in this compound. The relevance of these results for the interpretation of Mössbauer spectra observed after high-dose Te implantation in GaAs is discussed.     

119Sn Mössbauer spectroscopy of U x Th1−x CoSn and UCoAl1−x Sn x

Magnetization and¹¹⁹Sn Mössbauer spectroscopy studies were performed on two pseudoternary systems, namely U _x Th_1?x CoSn and UCoAl_1?x Sn _x . Magnetic hyperfine fields on¹¹⁹Sn nuclei were found to be due to local surrounding of U atoms which carry magnetic moments. In pure UCoSn the valuesB _hf=8.66 T and μ_∪ satisfy the relationB _hf=6.75 μ_B found for a number of UTX compounds studied. Local surrounding effects are indicated by multicomponent spectra obtained for the two pseudoternary series.     

Off-center Sn Atoms in PbSnTeSe Studied by the Mössbauer Effect

The quaternary semiconducting system, Pb_0.8Sn_0.2Te_0.8Se_0.2, has been studied by the Mössbauer effect method. The temperature dependence of the quadrupole splitting of ¹¹⁹Sn Mössbauer spectra has been obtained throughout a cooling and heating cycle of the sample. It is shown that the QS(T) during the cooling-heating cycle has a hysteretic form.     

Tin-doped spinel-related oxides of composition M3O4 (M = Mn, Fe, Co)

Tin-doped compounds of spinel-related M₃O₄ (M = Fe, Mn, Co) have been studied by ¹¹⁹Sn and ⁵⁷Fe Mössbauer spectroscopy in the temperature range of 20–600 K. The ¹¹⁹Sn Mössbauer spectra recorded down to 20 K from the non-iron-containing compounds of Co₃O₄ and Mn₃O₄ contained only doublets showing no transfer of magnetic properties from cobalt or manganese to the dopant tin ions. In contrast, the tin-doped-(FeCo)₃O₄ and (FeMn)₃O₄ gave ¹¹⁹Sn and ⁵⁷Fe Mössbauer spectra, which showed magnetic hyperfine interactions. The Curie temperature has been estimated for the former sample.     

Transferred hyperfine fields at 119Sn in Fe1−xMxSn [M≡Mn, Co and Ni]

The transferred hyperfine fields at ¹¹⁹Sn, using Mössbauer spectroscopy are reported for the hexagonal B-35 compounds with a general formula Fe_1?xM_xSn, where MMn, Co and Ni. In these compounds, Sn atoms occupy two crystallographically inequivalent sites. For FeSn the observed spectrum consists of a quadrupole doublet and a magnetic pattern corresponding to 2(d) and 2(a) sites respectively. The data have been analysed to resolve the controversy regarding hyperfine parameters. On replacing Fe by Mn atoms, additional lines appear in the higher velocity region of the Mössbauer spectrum and the intensity of the nuclear Zeeman pattern increases at the expense of quadrupole doublet. The resulting Mössbauer spectra have been analysed by taking only the nearest neighbour interactions into account. This analysis shows that on replacing each Fe atom by a Mn atom, the hyperfine field at 1(a) Sn site increases by about 40 kOe and a field of about 35 kOe is produced at the 2(d) Sn sites. Further, from the nuclear Zeeman pattern for 2(d) sites, the sign of quadropole splitting for these sites could also be determined and was found to be positive. However, the substitution of Co and Ni in place of Fe atoms results in a broad unresolved pattern suggesting that the hyperfine field at the 1(a) sites decreases and a finite field develops at the 2(d) site. The origin of transferred hyperfine fields at the two inequivalent Sn sites is discussed, the magnetic transition temperatures of these compounds have been estimated and the magnetic moments of M-atoms have been inferred.     

Characterization of the kinetics of Fe (II) binding by the R2 protein subunit of E. coli ribonucleotide reductase

¹¹⁹Sn Mössbauer spectroscopy was used to study Sn_1???x ⁵⁷Fe _x O_2???δ and Fe _x Sb _y Sn_1???x???y O_2???δ sol–gel synthesized ferromagnetic powders. ¹¹⁹Sn Mössbauer spectra of powder samples showed envelopes characteristic of a relatively broad Sn(IV) line. Small but significant differences can be found among the spectra belonging to different compositions and heat treatments. The spectra were decomposed into two doublets, one of these with unusually high quadrupole splitting was assigned to the defects playing very important role in the realisation of ferromagnetism in these materials.     

An ESCA study of Sn organometallic compounds: Solid state broadening effects

X-ray photoelectron spectra have been recorded for a number of solid and gaseous organotin compounds. Solid-state charging effects (such as differential charge broadening) can be large, though we have almost eliminated them by subliming very thin films onto platinum metal. In this way, we have obtained solid-state Sn 3d line widths that are within 10% of the analogous gas-phase values. The quality and reproducibility of the solid-state spectra likewise approach those of gases.The general correlation between ESCA Sn 3d line widths and Mössbauer quadrupole splittings indicates that the broadening of the Sn 3d lines is due to crystal-field splitting from the C₂⁰ term (the quadrupole term) in the crystal-field expansion. There is a general correlation between ESCA binding energies and Mössbauer isomer shifts for the solids.     

Interpretation of the 119Sn Mössbauer parameters

The variations of the ¹¹⁹Sn Mössbauer isomer shift δ are interpreted for tin compounds from a semi-empirical tight-binding calculation of the electronic density at the nucleus ρ(0). A molecular model is proposed in order to relate the variations of ρ(0) for the Sn(IV) chalcogenides to the changes in the Sn environment. The variations of the experimental values of the quadrupole splitting δ are linearly correlated to the values of the electric field gradients (EFG) calculated by the full-potential linearized-augmented-plane-wave (FP-LAPW) method. The value of the ¹¹⁹Sn nuclear quadrupole moment is found to be |Q| = 10.5 ± 0.2 fm². Finally, the relation between the EFG and the Sn environment is discussed for SnO.     

Confirmation of the oxygen defect in the Chevrel-phase SnMo6S8 from 119Sn Mössbauer spectroscopy

We report the measurement of ¹¹⁹Sn Mössbauer spectra in both the pure and oxygen-containing Chevrel-phase ternary superconductor SnMo₆S₈. A detailed analysis provides microscopic confirmation that Sn sites are associated with an oxygen-containing point defect. The isomer shift and quadrupole interaction for the oxygen-free Sn site (Sn1) and oxygen associated Sn site (Sn2) are sufficiently distinct to identify the two sites. It is shown that the reduction in T_c by substitution of oxygen for sulfur in the Chevrel phases is not due to charge transfer from the metal ion.     

Magnetic hyperfine fields at Fe,Cd and Sn sites in an FeCo alloy

The magnetic hyperfine field at an Fe site in the ferromagnetic alloy Fe_0.475Co_0.525 was measured using the Mössbauer effect. The value obtained at room temperature was 343 kOe. The hyperfine field at a substituted Cd impurity was measured by the method of time differential perturbed angular correlations. A single frequency was observed at room temperature, corresponding to a field of -177 kOe. Using the Mössbauer effect, the Sn site hyperfine field was measured in a sample in which 0.3 atomic percent of ¹¹⁹Sn had been substituted. The room temperature spectrum consisted of the superposition of a single line, together with a six-line hyperfine spectrum, corresponding to a field of 231 kOe. A phenomenological interpretation is proposed for Fe, Cd and Sn fields in the binary alloys of iron.     

Determination of the quadrupole splitting of the first excited state of 119Sn in β-tin by the e- -γ TDPAC technique

It is shown that for the determination of the quadrupole splitting (ω₀ = 28.5 ± 1.0 MHz) of the first excited 23.8 keV state of ¹¹⁹Sn in β-tin the e^- -γ time-differential perturbed angular correlation technique is superior to the Mössbauer method.     

Radiogenic Sn defects in ion-implanted CdTe

Radioactive^119mCd⁺ and¹¹⁹In⁺ ions have been implanted into CdTe single crystals at temperatures between 50–300K. Radiogenic defects formed with the daughter¹¹⁹Sn have been investigated by Mössbauer spectroscopy of the emitted 24 keV γ radiation. All Mössbauer spectra could be analysed consistently with three lines. These are proposed to be due to substitutional Sn on Cd sites in two different charge states and to Sn-vacancy complexes. The corresponding In-parent vacancy complexes anneal at 120K and above 300K.     

First Principles Calculations of Mössbauer Spectra of Intermetallic Anodes for Lithium-Ion Batteries

Changes in ¹¹⁹Sn and ¹²¹Sb Mössbauer spectra due to lithium insertion in tin and antimony based anode materials for lithium-ion batteries are analysed. Due to the complexity of the spectra linear augmented plane wave calculations of the electronic density were used to evaluate the electron density and the electric field gradients at the nucleus. The ¹¹⁹Sn Mössbauer spectrum of SnO+3.5 Li was evaluated from the theoretical spectra of the Li–Sn alloys. The observed good agreement between experimental and ab initio spectra is consistent with the reversible lithium insertion mechanism based on the formation of Li–Sn alloys. The analysis of the ¹²¹Sb Mössbauer spectra for Li insertion into CoSb₃ is somewhat more complex but calculations of the Mössbauer parameters clearly indicate the existence of Li₃Sb at the end of the first discharge.

     

99Ru,61Ni,57Fe,and119Sn Mössbauer studies of Heusler alloys containing ruthenium

⁹⁹Ru,⁶¹Ni,⁵⁷Fe and¹¹⁹Sn Mössbauer spectroscopic studies were made on ternary intermetallic compounds containing ruthenium, Ru_xY_3?xZ (Y=Fe, Ni; Z=Si, Sn). In the system of Ru_xFe_3?xSi, two different hyperfine magnetic fields were observed at the⁹⁹Ru nuclei (H _hf[Ru]) in the range ofx≤1.0 and the magnitude of eachH _hf[Ru] was found to decrease with an increase in the ruthenium concentrationx. Both the⁹⁹Ru and¹¹⁹Sn Mössbauer spectra of Ru₂FeSn could be analyzed with two sets of magnetically split lines. The⁶¹Ni Mössbauer spectra of Ru₂NiSn were obtained at 5 and 77 K.     

Mössbauer study of tin compounds related to highT c superconductors

¹¹⁹Sn Mössbauer spectroscopy was used to study an 1-2-4 type material of composition of SnSr₂Ca_0.5Y_0.5Cu₃O_8+d as well as the precursor SnO. The Mössbauer parameters of the precursor differed from those of the 1-2-4 material. With the 1-2-4 material an abrupt break-down was observed in the electrical resistivity curve at 76 K. No corresponding change could be shown in the Mössbauer parameters.     

Mössbauer insight to metallurgy, materials science and engineering

A brief overview of the contributions which Mössbauer effect spectroscopy has made to areas of materials science is presented. A survey of the literature reveals the decreasing trends of established areas, with emergence in the past decade or so of new areas such as nanostructured materials and materials produced by mechanochemical treatment and the continuing importance of rare-earth magnetic materials. Examples of applications of ⁵⁷Fe and ¹¹⁹Sn Mössbauer spectroscopy, both transmission and backscattering, are discussed. The complementary nature of Mössbauer spectroscopy and neutron diffraction in delineation of the magnetic behaviour and structures of materials is demonstrated by the La_1?x Y _x Mn₂Si₂ series of rare-earth intermetallic compounds.     

A tin-119 Mössbaer spectroscopic study of tin-doped niobium titanium phosphate

¹¹⁹Sn Mössbauer spectroscopy shows that the reaction of metallic tin with niobium titanium phosphate, NbTiP₃O₁₂, results in the accommodation of Sn²⁺ in two types of sites within channels in the NbTiP₃O₁₂ structure. The Sn²⁺ absorptions are characterised by highly positive chemical isomer shifts which decrease as increasing concentrations of Sn²⁺ are incorporated within the NbTiP₃O₁₂ structure. At very high tin concentrations the Mössbauer spectra show the presence of some unreacted elemental tin. The¹¹⁹Sn Mössbauer data are endorsed by X-ray powder diffraction data and are discussed in terms of the incorporation of highly ionic Sn²⁺ species.