The Structure of Thorium(IV) Dititanium(IV) Oxide, ThTi206

The crystal structure of a modification of ThTbOG, obtained from the melt at 1100 °C, has been analysed by X-ray diffraction and refined to the R value of 0.051. The crystals are monoclinic with a= 1.0799(7), b = 0.8570(6), c = 0.5192(3) nm and p = 115.29(3)0 , space group C2/c, Z = 4, F(OOO) = 728. The structure is based on a near-hexagonal close-packing of the oxygen atoms, with the thorium and titanium atoms in »octahedral sites«. The coordination polyhedron of Th is a distorted square antiprism with Th-0 distances from 0.232 to 0.265 nm, that of Ti a distorted octahedron with Ti-0 distances from 0.187 to 0.201 nm like those characteristic for Ti02 polymorphs. The Ti coordination polyhedra form layers parallel_to the (100) which are connected by zig-zag chains of the Th coordination polyhedra which run in the [001] direction. The relations to another ThTi20 6 polymorph structure1 (isomorphous with brannerite) have been examined

The High Pressure Behavior of Galenobismutite, PbBi₂S₄: A Synchrotron Single Crystal X-ray Diffraction Study

High-pressure single-crystal synchrotron X-ray diffraction data for galenobismutite, PbBi2S4 collected up to 20.9 GPa, were fitted by a third-order Birch-Murnaghan equation of state, as suggested by a FE-fE plot, yielding V0 = 697.4(8) Å3, K0 = 51(1) GPa and K’ = 5.0(2). The axial moduli were M0a = 115(7) GPa and Ma’ = 28(2) for the a axis, M0b = 162(3) GPa and Mb’ = 8(3) for the b axis, M0c = 142(8) GPa and Mc’ = 26(2) for the c axis, with refined values of a0, b0, c0 equal to 11.791(7) Å, 14.540(6) Å 4.076(3) Å, respectively, and a ratio equal to M0a:M0b:M0c = 1.55:1:1.79. The main structural changes on compression were the M2 and M3 (occupied by Bi, Pb) movements toward the centers of their respective trigonal prism bodies and M3 changes towards CN8. The M1 site, occupied solely by Bi, regularizes the octahedral form with CN6. The eccentricities of all cation sites decreased with compression testifying for a decrease in stereochemical expression of lone electron pairs. Galenobismutite is isostructural with calcium ferrite CaFe2O4, the suggested high pressure structure can host Na and Al in the lower mantle. The study indicates that pressure enables the incorporation of other elements in this structure, increasing its potential significance for mantle mineralogy

The High-Pressure Phase Transition in Jamesonite: A Single-Crystal Synchrotron X-ray Diffraction Study

The high-pressure behavior of jamesonite (FePb4Sb6S14, a = 4.08(3) Å, b = 19.08(3) Å, c = 15.67(3) Å, β= 91.89°, space group P21/c) has been investigated using in situ HP synchrotron X-ray single-crystal diffraction up to ~17 GPa with a diamond anvil cell under hydrostatic conditions. Results of the volume isothermal equation of state (EoS), determined by fitting the P-V data with a third-order Birch–Murnaghan (BM) EoS, are V0 = 1207.1(4) Å3, K0 = 36(1) GPa and K’ = 5.7(7). At high pressure, jamesonite undergoes a phase transition to an orthorhombic structure with a Pmcb space group (β-jamesonite). The analysis of β-jamesonite’s compressibility up to 16.6 GPa, studied by fitting the data with a second-order BM-EoS, gives V0 = 1027(2) Å3, K0 = 74(2) GPa. The comparison of the structural refinements at different pressures indicates that Fe, Pb and Sb do not change their coordination number over the whole investigated P range, respectively, 6 for Fe, 7 and 8 for Pb and 5 + 2 for Sb. However, a significant change occurs on the orientation of Sb lone electron pairs upon the phase transition in accordance with the change in symmetry. Furthermore, a discontinuity in the Fe chain evolution at the transition pressure is observed

A Novel Synthesis Routine for Woodwardite and Its Affinity towards Light (La, Ce, Nd) and Heavy (Gd and Y) Rare Earth Elements

A synthetic Cu-Al-SO4 layered double hydroxide (LDH), analogue to the mineral woodwardite [Cu1−xAlx(SO4)x/2(OH)2·nH2O], with x < 0.5 and n ≤ 3x/2, was synthesised by adding a solution of Cu and Al sulphates to a solution with NaOH. The pH values were kept constant at 8.0 and 10.0 by a continuous addition of NaOH. The material obtained had poor crystallinity, turbostratic structure, and consisted of nanoscopic crystallites. The analyses performed in order to characterise the obtained materials (X-ray diffraction (XRD), thermogravimetry (TG), and Fourier Transform Infra-Red (FTIR) spectroscopy) showed that the Cu-Al-SO4 LDH is very similar to woodwardite, although it has a smaller layer spacing, presumably due to a lesser water content than in natural samples. The synthesis was performed by adding light rare earth elements (LREEs) (La, Ce, and Nd) and heavy rare earth elements (HREEs) (Gd and Y) in order to test the affinity of the Cu-Al-SO4 LDH to the incorporation of REEs. The concentration of rare earth elements (REEs) in the solid fraction was in the range of 3.5–8 wt %. The results showed a good affinity for HREE and Nd, especially for materials synthesised at pH 10.0, whereas the affinities for Ce and La were much lower or non-existent. The thermal decomposition of the REE-doped materials generates a mixture of Cu, Al, and REE oxides, making them interesting as precursors in REE oxide synthesis