Comparison of Uranium(VI) and Thorium(IV) Silicates Synthesized via Mixed Fluxes Techniques

Abstract

Two uranium and two thorium silicates were obtained using high temperature mixed fluxes methods. K(UO)SiO crystallizes in the P2/ c space group and contains open-branched sechser (six) single silicate chains, whereas K(UO)SiO crystallizes in the C2/ c space group and is built of unbranched achter (eight) silicate chains. The crystals of K(UO)SiO and K(UO)SiO are related by increasing U/Si molar ratios, and both structures contain the same secondary building units (SBUs), [USi] heptamers. The triangle diagram for all known A-UO-SiO phases demonstrates the high polymerization level of silicate groups in the system, which was compared with the family of A-UO-BO/BO compounds. For both thorium silicates, the transformation of KThSiO to KThSiO was found to be a factor of the reaction time. KThSiO crystallizes in the C2/ c space group and belongs to the NaSiSiO structure type. Its 3D framework consists of diorthosilicate SiO group and ThO octahedra. Noncentrosymmetric KThSiO crystallizes in the hexagonal P6 space group and adopts mineral wadeite-type structure based upon triorthosilicate SiO rings and ThO octahedra. The coordination environment of thorium for all existing oxo-anion compounds including B, Si/Ge, P/As, Cr/Mo/W, and S/Se/Te are summarized and analyzed. Additionally, spectroscopic properties of all novel materials have been studied.

Formation of Open Framework Uranium Germanates: The Influence of Mixed Molten Flux and Charge Density Dependence in U-Silicate and U-Germanate Families

“…The structure of K 2 (UO 2 )­GeO 4 consists of the following primary building units (PUBs): one uranyl tetragonal bipyramid, one germanate tetrahedron, and two potassium cations. The UO 6 tetragonal bipyramid displays the typical UO Ur and U–O eq bond distances, which agree well with other inorganic uranyl compounds and are 1.820(4) Å for axial bonds and 2.247(3) Å for equatorial bonds. , The Ge–O bond length in GeO 4 tetrahedra is 1.751(3) Å, and O–Ge–O angles are 106.2(1)° and 116.2(2)°. The two potassium cations are six-fold and eight-fold coordinated, respectively.…”

Framework Uranyl Silicates: Crystal Chemistry and a New Route for the Synthesis

“…Condensation of the monomeric tetrahedra via vertex sharing leads to formation of linear [Si8O20] 8− ribbons (Figure 1j) [13][14][15][16][17][18]. As in the previous case, a single structure can host polymeric anions with different compositions and architectures [19]. [19], tubular, and multi-layer chains like…”

“…1j) [13][14][15][16][17][18]. As in the previous case, a single structure can host polymeric anions with different compositions and architectures [19].…”

“…As in the previous case, a single structure can host polymeric anions with different compositions and architectures [19]. [19], tubular, and multi-layer chains like…”

Flux Growth of Uranyl Titanates: Rare Examples of TiO4 Tetrahedra and TiO5 Square Bipyramids

“…For much of their history, the focus was on the investigation of uranyl minerals and the exploration of new materials through ceramic and hydrothermal syntheses, the latter of which resembles the conditions under which most minerals form. In the past decade, the flux growth of uranyl compounds, especially using halide fluxes, has become quite prolific, resulting in many new uranyl silicates, − germanates, − phosphates, − borates, − aluminates, and others. ,, …”