Alkali Tin Research Articles

Alkali Tin Halides: Exploring the Local Structure of A2SnX6 (A = K, Rb; X = Cl, Br, I) Compounds Using Solid-State NMR and DFT Computations

Alkali Tin Halides: Exploring the Local Structure of A₂SnX₆ (A = K, Rb; X = Cl, Br, I) Compounds Using Solid-State NMR and DFT Computations

Tin(II)-Induced Large Birefringence Enhancement in Metal Phosphates.

Two alkali tin(II) phosphates, namely, Rb[SnF(HPO4)] and Rb(Sn3O)2(PO4)3, were synthesized through mild hydrothermal methods. They belong to the orthorhombic Pnma and Pbcn space groups, respectively. Rb[SnF(HPO4)] features a layered structure based on 1D [SnF(HPO4)]∞ chains interconnected by hydrogen bonds, with Rb+ cations located at the interlayer space. For Rb(Sn3O)2(PO4)3, each pair of [Sn3O]4+ clusters is bridged by a pair of [P(1)O4]3- tetrahedra to build a 1D [Sn-P-O]∞ chain. These 1D [Sn-P-O]∞ chains are further cross-linked though [P(2)O4]3- tetrahedra to construct a 3D network with 7- and 10-membered-ring channels. The tin(II) ions in Rb[SnF(HPO4)] and Rb(Sn3O)2(PO4)3 with stereochemically active lone pairs (SCALPs) significantly enhance the birefringences of metal phosphates: Δn = 0.147@1064 nm for Rb[SnF(HPO4)] and 0.082@1064 nm for Rb(Sn3O)2(PO4)3.

First-principle studies of the optoelectronic properties of ASnF3 (A = Na, K, Rb and Cs)

In this paper, we communicate a new type of Auger-free luminescence (AFL) compounds, alkali tin fluorides ASnF3 (A = Na, K, Rb and Cs). The luminescence in these compounds originates due to the electron transition from the top valence band (VB) of tin-[Formula: see text] orbital to the outermost core levels of halogen, i.e., halogen-[Formula: see text] orbital ([Formula: see text]-[Formula: see text] transitions). The AFL of these compounds is expected to be of L-type. Furthermore, the electronic band structures and optical properties such as dielectric functions, refractive index and energy loss function are also investigated using ab initio calculations.

Structure and Characterization of a Zero-Dimensional Alkali Tin Dihalides Compound Cs3Sn3F2Cl7 with the [Sn2F2Cl4]2- Clusters.

A new perovskite stoichiometric alkali tin dihalides compound, Cs3Sn3F2Cl7, is synthesized by a hydrothermal method. This compound belongs to the monoclinic space group of P21/c with cell parameters of a = 9.5645(4) Å, b = 14.2057(7) Å, c = 13.5828(6) Å, and β = 93.2450(10)°. Unlike the common perovskites in which octahedra are interconnected to be a three-dimensional network, Cs3Sn3F2Cl7 possesses a zero-dimensional structure consisting of Cs+ cations, isolated [SnCl3]- trigonal pyramids, and dimer structural units [Sn2F2Cl4]2-; the latter microscopic unit is found for the first time. The thermal stability and UV-vis-NIR diffuse reflectance spectroscopy in Cs3Sn3F2Cl7 are measured, and the electronic structure is calculated. Interestingly, the 5s2 lone-pair electrons on Sn2+ cations are stereochemically active, which results in a pretty good photocatalytic activity of the title compound.

An alkaline tin(II) halide compound Na3Sn2F6Cl: Synthesis, structure, and characterization

A new alkali tin(II) halide compound, Na3Sn2F6Cl, is synthesized by hydrothermal method. This compound crystallizes trigonally in space group of R-3c (167), and processes a zero-dimensional (0D) structure consisted of Na+ cations, Cl− anions and the isolated [SnF3]- trigonal pyramids in which the stereochemically active 5s2 lone pair electrons are attached to the Sn2+ cations. Interestingly, the [SnF3]− trigonal pyramids are parallel arranged in the a-b plane, while oppositely arranged in line with rotation along the c- axis. Moreover, the energy bandgap, thermal stability and electronic structure of Na3Sn2F6Cl are characterized and the results reveal that this compound has and indirect bandgap of 3.88eV and is stable under 270°C.

Synthesis and characterization of ASnF3 (A=Na+, K+, Rb+, Cs+)

A family of alkali metal tin(II) fluorides, ASnF3 (A=Na+, K+, Rb+, or Cs+), has been synthesized through a low temperature solvothermal technique. A fluorine free solvent, methanol, was used in the synthesis. NaSnF3, KSnF3, and RbSnF3 have been reported previously; however for RbSnF3 the reported space group is incorrect. CsSnF3 is a new alkali tin(II) fluoride, and exhibits a ‘zero-dimensional’ crystal structure with isolated SnF3− anions separated by Cs+ cations. In addition to the synthesis, infrared, UV–vis, thermogravimetric and differential thermal analysis measurements were performed.

Durability of Borosilicate Glass Compositions for the Immobilisation of the UK's Separated Plutonium Stocks

AbstractSeveral glass compositions are currently under investigation for immobilisation of the separated PuO2 that has been produced as a result of civil nuclear fuel reprocessing in the UK. Whilst a final decision on the fate of what ultimately will be over 100 tonnes of plutonium has yet to be made, all options for the disposition of this material are currently being investigated by Nexia Solutions Ltd on behalf of the Nuclear Decommissioning Authority (NDA).As one of the immobilisation options, vitrification in borosilicate glass could potentially provide a criticality-safe and stable waste form with durability suitable for long term storage and subsequent repository disposal. From an initial experimental survey of potential candidates, three borosilicate compositions were selected for a more detailed study of the waste loading and chemical durability: lanthanide borosilicate (LaBS), alkali tin silicate (ATS) and high-lanthanide alkali borosilicate (modified-MW). In these inactive tests, hafnium was used as the surrogate for plutonium. This paper describes a range of static leach tests that were undertaken in order to understand the overall durability of the waste forms, as well as the release rates of the Pusurrogate when compared to any neutrons poisons present in the glass. For the LaBS compositions it was found that the release rate of gadolinium was potentially slightly higher than that of hafnium, although both were as low as 10-5 to 10-6 g m2 day-1. The potential implications for long-term repository behaviour are discussed.

Development of Borosilicate Glass Compositions for the Immobilisation of the UK's Separated Plutonium Stocks

AbstractThe UK inventory of separated civil plutonium is expected to exceed 100 tonnes by 2010. Whilst the majority of this could be used in the manufacture of MOx (Mixed Oxide) fuel in future power generation scenarios, options for the disposal of surplus plutonium are currently being investigated by Nexia Solutions Ltd on behalf of the UK's Nuclear Decommissioning Authority (NDA). One of the options being considered is immobilisation in a durable glass matrix followed by long term storage and subsequent final repository disposal.A preliminary experimental survey assessed a selection of potential glass systems on the basis of Pu-surrogate (cerium) loading, durability, and ease of processing. Following this, a number of borosilicate compositions have been taken forward into a more detailed investigation in order to fully qualify their potential for Pu-immobilisation. The selected compositions are lanthanide borosilicate (LaBS), alkali tin silicate (ATS) and high-lanthanide alkali borosilicate (modified-MW). For this second series of experiments, hafnium was selected as the Pu surrogate, and a study of the potential waste loading as a function of temperature for the three selected compositions is described in this paper. Furthermore, several variations of the LaBS composition were fabricated in order to investigate the effect of total lanthanide content on melting temperature. The benchmark of 10 wt% HfO2 incorporation is achievable for all three glasses with temperatures of 1200, 1300 and 1400 °C required for ATS, modified-MW and LaBS respectively.

Structural and electronic properties of liquid alkali–tin alloys

There is a debate about the preservation of tetrahedral polyanions formed in crystalline equiatomic (Na/K/Rb/Cs)–(Sn/Pb) compounds on melting. Diffraction experiments demonstrate the existence of a narrow first diffraction peak in the static structure factor indicative of local ordering. On the other hand reverse Monte-Carlo calculations and classical as well as quantum-mechanical simulations have failed to confirm the existence of polyanionic complexes in a liquid phase. We present ab initio local density functional studies of the structural and electronic properties of crystalline and liquid (Li/Na/K)–Sn alloys. While our calculations demonstrate the existence of tetrahedral complexes in KSn, for NaSn they agree with previous conclusions that the Sn 4 4−-tetrahedra are distorted or even destroyed in the liquid. For the liquid LiSn alloy we demonstrate that, due to the small size of the Li-ion, interactions between the Sn-ions destabilize the polyanionic order.

Investigations on sodium tin phosphate and tin pyrophosphate glasses

Glasses of the alkali tin phosphate system have been investigated. The infrared absorption and fluorescence spectra of the glasses have been examined. It is found that tin is present in both+2 and+4 oxidation states. Also tin ions occupy four- or six-coordinated sites in the glass.