Atom Probe Tomography Investigation of Clustering in Model P2O5-Doped Borosilicate Glasses for Nuclear Waste Vitrification.

Atom probe tomography (APT) has been utilized to investigate the microstructure of two model borosilicate glasses designed to understand the solubility limits of phosphorous pentoxide (P2O5). This component is found in certain high-level radioactive defence wastes destined for vitrification, where phase separation can potentially lead to a number of issues relating to the processing of the glass and its long-term chemical and structural stability. The development of suitable focused ion beam (FIB)-preparation routes and APT analysis conditions were initially determined for the model glasses, before examining their detailed microstructures.

Synthesis and characterisation of the vibrational and electrical properties of antiferromagnetic 6L-BaCoTeO ceramics.

Optimal processing conditions for fabrication of dense single-phase 6L-BaCoTeO ceramics via the solid-state reaction method were determined. These ceramics possess a room-temperature crystal structure described by the centrosymmetric P3[combining macron]m1 space group. Polarized Raman spectroscopy enabled the observation of all the 25 predicted Raman modes and assignment of their symmetries.

Crystal structures of K[XSiO] (X = Fe, Co, Zn) and Rb[XSiO] (X = Mn) leucites: comparison of monoclinic P2/c and Ia{\overline 3}d polymorph structures and inverse relationship between tetrahedral cation (T = Si and X)-O bond distances and intertetrahedral T-O-T angles.

The leucite tectosilicate mineral analogues KXSiO (X = Fe, Co, Zn) and RbXSiO (X = Mn) have been synthesized at elevated temperatures both dry at atmospheric pressure and at controlled water vapour pressure; for X = Co and Zn both dry and hydrothermally synthesized samples are available. Rietveld refinement of X-ray data for hydrothermal KXSiO (X = Fe, Co, Zn) samples shows that they crystallize in the monoclinic space group P2/c and have tetrahedral cations (Si and X) ordered onto distinct framework sites [cf. hydrothermal KMgSiO; Bell et al.

Rietveld refinement of the crystal structures of Rb2 XSi5O12 (X = Ni, Mn).

The synthetic leucite silicate framework mineral analogues Rb2 XSi5O12 {X = Ni [dirubidium nickel(II) penta-silicate] and Mn [dirubidium manganese(II) penta-silicate]} have been prepared by high-temperature solid-state synthesis. The results of Rietveld refinements, using X-ray powder diffraction data collected using Cu Kα X-rays, show that the title compounds crystallize in the space group Pbca and adopt the cation-ordered structure of Cs2CdSi5O12 and other leucites. The structures consist of tetra-hedral SiO4 and XO4 units sharing corners to form a partially substituted silicate framework.

Sr-fresnoite determined from synchrotron X-ray powder diffraction data.

The fresnoite-type compound Sr2TiO(Si2O7), distrontium oxidotitanium disilicate, has been prepared by high-temperature solid-state synthesis. The results of a Rietveld refinement study, based on high-resolution synchrotron X-ray powder diffraction data, show that the title compound crystallizes in the space group P4bm and adopts the structure of other fresnoite-type mineral samples with general formula A2 TiO(Si2O7) (A = alkaline earth metal cation). The structure consists of titanosilicate layers composed of corner-sharing SiO4 tetra-hedra (forming Si2O7 disilicate units) and TiO5 square-based pyramids.

Rietveld refinement of Sr(5)(AsO(4))(3)Cl from high-resolution synchrotron data.

The apatite-type compound, penta-strontium tris-[arsenate(V)] chloride, Sr(5)(AsO(4))(3)Cl, has been synthesized by ion exchange at high temperature from a synthetic sample of mimetite [Pb(5)(AsO(4))(3)Cl] with SrCO(3) as a by-product. The results of the Rietveld refinement, based on high resolution synchrotron X-ray powder diffraction data, show that the title compound crystallizes in the same structure as other halogenoapatites with general formula A(5)(YO(4))(3)X (A = divalent cation, Y = penta-valent cation, and X = F, Cl or Br) in the space group P6(3)/m. The structure consists of isolated tetra-hedral AsO(4) (3-) anions (the As atom and two O atoms have m symmetry), separated by two crystallographically independent Sr(2+) cations that are located on mirror planes and threefold rotation axes, respectively.

Polymorphism in cyclohexanol.

The crystal structures and phase behaviour of phase II and the metastable phases III' and III of cyclohexanol, C(6)H(11)OH, have been determined using high-resolution neutron powder, synchrotron X-ray powder and single-crystal X-ray diffraction techniques. Cyclohexanol-II is formed by a transition from the plastic phase I cubic structure at 265 K and crystallizes in a tetragonal structure, space group P42(1)c (Z' = 1), in which the molecules are arranged in a hydrogen-bonded tetrameric ring motif. The structures of phases III' and III are monoclinic, space groups P2(1)/c (Z' = 3) and Pc (Z' = 2), respectively, and are characterized by the formation of hydrogen-bonded molecular chains with a threefold-helical and wave-like nature, respectively.

Rietveld refinement of Ba(5)(AsO(4))(3)Cl from high-resolution synchrotron data.

The apatite-type compound Ba(5)(AsO(4))(3)Cl, penta-barium tris-[arsenate(V)] chloride, has been synthesized by ion exchange at high temperature from a synthetic sample of mimetite (Pb(5)(AsO(4))(3)Cl) with BaCO(3) as a by-product. The results of the Rietveld refinement, based on high resolution synchrotron X-ray powder diffraction data, show that the title compound crystallizes in the same structure as other halogenoapatites with general formula A(5)(YO(4))(3)X (A = divalent cation, Y = penta-valent cation, X = Cl, Br) in space group P6(3)/m. The structure consists of isolated tetra-hedral AsO(4) (3-) anions (m symmetry), separated by two crystallographically independent Ba(2+) cations that are located on mirror planes and threefold rotation axes, respectively.

High-performance X-ray detectors for the new powder diffraction beamline I11 at Diamond.

The design and performance characterization of a new light-weight and compact X-ray scintillation detector is presented. The detectors are intended for use on the new I11 powder diffraction beamline at the third-generation Diamond synchrotron facility where X-ray beams of high photon brightness are generated by insertion devices. The performance characteristics of these detection units were measured first using a radioactive source (efficiency of detection and background count rate) and then synchrotron X-rays (peak stability, light yield linearity and response consistency).