IRREGULARITIES OF YTTERBIUM UNDER HIGH-PRESSURE

Phase transitions of the rare-earth metal ytterbium were studied under pressure up to 70 GPa at room temperature with an energy-dispersive x -ray-diffraction technique using synchrotron radiation. A new phase tr ansition hcp-->fcc(II) was observed at 57 GPa. The phase sequence with pressure up to 70 GPa is fcc(I)-->bcc-->hcp-->fcc(II). The hcp and fc c(II) phases show some similarity in their compression behavior to the lower pressure phases of praseodymium which is considered as first ev idence for a strong hybridization between f electrons and conduction e lectrons.