Effect of Pressure on Electrical Resistance of Ten Rare-Earth Metals

The pressure equipment used in this investigation was a Drickamer-type apparatus with sintered diamond compacts. The pressure calibration was established by using p vs. (L. Go) calibration diagram. The electrical resistance behavior of ten rare-earth metals (Pr, Nd, Sm, Gd, Tb, Dy, Ho, Tm, Lu and Yb) was studied under high pressure up to 43 GPa and at room temperature. Some kinks and slope changes are found on the resistance vs. pressure curves and many of them are first experimentally discovered, which are perhaps related to the hcpSm-typedhcpfcc phase transitions. These new phase transition pressure are 14.0 GPa for Lu from hcp-Sm-type, 7.0 GPa for Gd, 12.0 GPa for Tb, 12.5 GPa for Dy, 13.0 GPa for Ho, 17.5 GPa for Tm, and 26.0 GPa for Lu from Sm-type to dhcp, 12.0 GPa for Sm, 17.5 GPa for Gd, 18.0 GPa for Tb, 22.0 GPa for Dy, 24.0 GPa for Ho, and 31.0 GPa for Tm from dhcp to fcc, respectively. For Gd and Tb there is a slope change on each R vs p curve at 22.0 and 24.5 GPa respectively. We believe that these two changes are associated with the phase transition from fcc to a new phase, dfcc, three slope changes at 14.5, 18.6 and 25.0 GPa are also found for Yb. The first change is related to valence change from divalent to trivalent, which is in agreement with the value calculated by Johansson et al. The second and the third changes should indicate hcp to Sm-type and Sm-type to dhcp transitions respectively.