High-Pressure Structural Studies of UC by X-Ray Diffraction and Synchrotron Radiation

摘要

High-pressure X-ray diffraction studies have been performed on UC powder for pressures up to 46 GPa using a diamond anvil cell and synchrotron radiation. The low-pressure phase is of NaCl-type with the lattice constant a/sub 0/=4.9606(5) A at ambient pressure. The bulk modulus and its pressure gradient are B/sub 0/=155(10) GPa and B/sub 0/'=7.9(14), respectively. A transformation to a new phase, UC II, has been found at about 27 GPa. The diffraction lines from the high-pressure phase can be indexed using a pseudo-bodycentred orthorhombic unit cell, which is a distortion of the body-centred tetragonal unit cell of the fcc lattice. The lattice constants at 33.6 GPa are a=3.043(10) A, b=3.518(16) A and c=4.730(7) A. The experimental equation of state has been compared with results of theoretical calculations. (ERA citation 12:041361)