High-Pressure X-Ray Diffraction Study on Electronics-dTransition in Zirconium

High-pressure X-ray diffraction study on the electronic s - d transition in IVa 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, K 0 , and the pressure derivative of K 0 , 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.