A laboratory-scale synthesis of UF4 is presented that utilizes the reduction of UF6 with sulfur in anhydrous hydrogen fluoride. An excess of sulfur can be removed by vacuum sublimation, yielding pure UF4 , as shown by powder X-ray diffraction, micro X-ray fluorescence analysis, infrared and Raman spectroscopy, as well as magnetic measurements. Furthermore, a single-crystalline, high-pressure modification of UF4 was obtained in a multi-anvil press at elevated temperatures. The high-pressure polymorph HP-UF4 was characterized by means of single-crystal and powder X-ray diffraction, as well as by magnetic measurements, and presents a novel crystal structure type. Quantum-chemical calculations show the HP-modification to be 10 kJ mol-1 per formula unit higher in energy compared to UF4 .
Keywords: actinoids; fluorine; high-pressure chemistry; magnetic properties; uranium.
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