HIGH-PRESSURE X-RAY-DIFFRACTION STUDY ON ELECTRONIC S-D TRANSITION IN ZIRCONIUM

High-pressure X-ray diffraction study on the electronic s-d transition in 1Va transition metal Zr has been carried out up to 68 GPa. The successive structural transitions of hcp-hexagonal-bcc were observed at 6.7 GPa and 33 GPa, respectively. An isostructural transition was also observed in the bcc phase around 56 GPa. The values of the isothermal bulk modulus, K0, and the pressure derivative of K0, K'0, for the hexagonal phase were calculated to be 121 GPa and 1.69, respectively. Abnormally small K'0 suggests softening in the pressure-volume curve. The atomic volume of the bcc-Zr at the transition pressure of 33 GPa agreed with that of the bcc-Nb at zero pressure. These results suggest that the s-d transition of Zr metal progresses at each pressure and is complete with an isostructural transition at 56 GPa.