Synthesis,Crystal Structures and Properties of a Uranium Silicate and a Uranium Phosphate

• Main Authors: Yu-chih Chang, 張育誌
• Other Authors: Kwang-hwa Lii
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/46544441224691865554

碩士 === 國立中央大學 === 化學學系 === 101 === A salt-inclusion mixed-valence uranium(V,VI) silicate,[Na9F2][(UVO2)(UVIO2)2(Si2O7)2](A1), and a uranium(IV) phosphate,Na10UIV2(PO4)6 (A2), was synthesized under hydrothermal condition at 585oCand 160MPa, and structurally characterized by powder and single X-raydiffraction. These compounds were further characterized by EDX, EPMA, XPS and SHG. Compound A1 is a novel uranium(V,VI) silicate. The structure caotains 2D sheet of uranyl sorosilicate with the composition [UO2Si2O7] which connected by U(1)VO6etragonal bipyramids to form thick layers. The Na+ cations are located at sites in the intralayer and interlayer regions. In adition to Na+ cations,the interlayer region also contains F- anions such that infinite chains with theformula FNa1/1Na4/2 are formed. The compound A1 is not only the first example of salt-inclusion metal silicate synthesized under high-temperature,high-pressure hydrothermal onditions, the first salt-inclusion mixed-valence uranium silicate, but also the first mixed-valence uranium(V,VI) silicate in the literature. Compound A2 is a new tetravalent uranium phosphates. The valence state of uranium was established by U 4f X-ray photoelectron spectroscopy. The structure contains UO8 snub-disphenoidal polyhedral which are linked to monophosphate tetrahedral bt vertex- and edge-sharing such that a 3D framework with 12-sided circular and rectangular channels is fromed. All ten sodium sites are situated inside the channels and are fully occupied. These are the first uranium(IV) phosphate synthesized under high-temperature, high-pressure hydrothermal condition.