Abstract
New actinide borates ThB4O8 and UB4O8 were synthesized under high-pressure, high-temperature conditions (5.5 GPa/1100 °C for thorium borate, 10.5 GPa/1100 °C for the isotypic uranium borate) in a Walker-type multianvil apparatus from their corresponding actinide oxide and boron oxide. The crystal structure was determined on basis of single-crystal X-ray diffraction data that were collected at room temperature. Both compounds crystallized in the monoclinic space group C2/c (Z=4). Lattice parameters for ThB4O8: a=1611.3(3), b=419.86(8), c=730.6(2) pm; β=114.70(3)°; V=449.0(2) Å3; R1=0.0255, wR2=0.0653 (all data). Lattice parameters for UB4O8: a=1589.7(3), b=422.14(8), c=723.4(2) pm; β=114.13(3)°; V=443.1(2) Å3; R1=0.0227, wR2=0.0372 (all data). The new AnB4O8 (An=Th, U) structure type is constructed from corner-sharing BO4 tetrahedra, which form layers in the bc plane. One of the four independent oxygen atoms is threefold-coordinated. The actinide cations are located between the boron–oxygen layers. In addition to Raman spectroscopic investigations, DFT calculations were performed to support the assignment of the vibrational bands.
Highlights
Over the last decade, our research into the high-pressure chemistry of borates has led to the synthesis of several new compounds with fascinating structures, owing to the efficient use of the multianvil technique.[1]
Synthesis and crystal-structure analysis: The compounds ThB4O8 and UB4O8 were synthesized from their corresponding actinide oxides and B2O3 under high-pressure, high-temperature conditions (5.5 GPa and 1100 8C for ThB4O8; 10.5 GPa and 1100 8C for UB4O8) in a 1000 ton multianvil press that was fitted with a Walker-type module
The two crystallographically distinguishable boron atoms in the actinide borates ThB4O8 and UB4O8 are tetrahedrally coordinated by four oxygen atoms
Summary
Our research into the high-pressure chemistry of borates has led to the synthesis of several new compounds with fascinating structures, owing to the efficient use of the multianvil technique.[1]. Synthesis and crystal-structure analysis: The compounds ThB4O8 and UB4O8 were synthesized from their corresponding actinide oxides and B2O3 under high-pressure, high-temperature conditions (5.5 GPa and 1100 8C for ThB4O8; 10.5 GPa and 1100 8C for UB4O8) in a 1000 ton multianvil press that was fitted with a Walker-type module.
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