¹¹9Sn Mössbauer spectroscopy study of the mechanism of lithium reaction with self-organized Ti1/2Sn1/2O2 nanotubes.

Novel self-organized Ti1/2Sn1/2O2 nanotubes can be produced by the electrochemical anodization of co-sputtered Ti-Sn thin-films. Combined X-ray photoelectron spectroscopy and (119)Sn Mössbauer spectroscopy of pristine samples evidenced the octahedral substitution of Sn(4+) for Ti(4+) in the TiO2 structure. In addition to the improved lithium storage behaviour of the Ti1/2Sn1/2O2 nanotubes, ex situ(119)Sn Mössbauer spectroscopy of cycled electrodes has sufficiently confirmed that no decomposition of the Ti1/2Sn1/2O2 structure occurred, and that no Li-Sn phase was formed during the discharge, corroborating that the electrochemical reaction is due exclusively to Li(+) insertion into the Ti1/2Sn1/2O2 nanotubes in the 1 ≤ U/V ≤ 2.6 voltage range.

A 3.90 V iron-based fluorosulphate material for lithium-ion batteries crystallizing in the triplite structure.

Li-ion batteries have empowered consumer electronics and are now seen as the best choice to propel forward the development of eco-friendly (hybrid) electric vehicles. To enhance the energy density, an intensive search has been made for new polyanionic compounds that have a higher potential for the Fe²âº/Fe³âº redox couple. Herein we push this potential to 3.90 V in a new polyanionic material that crystallizes in the triplite structure by substituting as little as 5 atomic per cent of Mn for Fe in Li(Fe(1-δ)Mn(δ))SO4F. Not only is this the highest voltage reported so far for the Fe²âº/Fe³âº redox couple, exceeding that of LiFePO4 by 450 mV, but this new triplite phase is capable of reversibly releasing and reinserting 0.7-0.8 Li ions with a volume change of 0.6% (compared with 7 and 10% for LiFePO4 and LiFeSO4F respectively), to give a capacity of ~125 mA h g⁻¹.

Synthesis of tin and tin oxide nanoparticles of low size dispersity for application in gas sensing.

Nanocomposite core-shell particles that consist of a Sn0 core surrounded by a thin layer of tin oxides have been prepared by thermolysis of [(Sn(NMe2)2)2] in anisole that contains small, controlled amounts of water. The particles were characterized by means of electronic microscopies (TEM, HRTEM, SEM), X-ray diffraction (XRD) studies, photoelectron spectroscopy (XPS), and Mossbauer spectroscopy. The TEM micrographs show spherical nanoparticles, the size and size distribution of which depends on the initial experimental conditions of temperature, time, water concentration, and tin precursor concentration. Nanoparticles of 19 nm median size and displaying a narrow size distribution have been obtained with excellent yield in the optimized conditions. HRTEM, XPS, XRD and Mossbauer studies indicate the composite nature of the particles that consist of a well-crystallized tin beta core of approximately equals 11 nm covered with a layer of approximately equals 4 nm of amorphous tin dioxide and which also contain quadratic tin monoxide crystallites. The thermal oxidation of this nanocomposite yields well-crystallized nanoparticles of SnO2* without coalescence or size change. XRD patterns show that the powder consists of a mixture of two phases: the tetragonal cassiterite phase, which is the most abundant, and an orthorhombic phase. In agreement with the small SnO2 particle size, the relative intensity of the adsorbed dioxygen peak observed on the XPS spectrum is remarkable, when compared with that observed in the case of larger SnO2 particles. This is consistent with electrical conductivity measurements, which demonstrate that this material is highly sensitive to the presence of a reducing gas such as carbon monoxide.

X-ray Diffraction and (119)Sn Mössbauer Spectroscopy Study of a New Phase in the Bi(2)Se(3)-SnSe System: SnBi(4)Se(7).

First studies of the ternary system SnSe-Bi(2)Se(3) developed in 1960s and 1970s have revealed the existence of a nonstoichiometric trigonal phase with a wide range of compositions. In this study, an almost stoichiometric phase, corresponding to the composition SnBi(4)Se(7), has been identified and isolated. The structure has been determined by X-ray diffraction and the local environment of Sn atoms analyzed by Mössbauer spectroscopy. This phase has a rhombohedral structure, space group R&thremacr;m, with hexagonal lattice parameters a = 4.1602(5) Å and c = 38.934(3) Å. The unit cell contains three slabs, each one composed of seven atomic layers according to the sequence Se-Bi-Se-(Bi,Sn)-Se-Bi-Se. Bismuth atoms partially occupy two sites, 3a (0, 0, 0) and 6c (0, 0, z) with z = 0.4285, while tin atoms partially occupy only one site, 3a. Selenium atoms are placed in two different 6c sites, with z(1) = 0.1350 and z(2) = 0.7108.