Reinvestigation of high pressure polymorphism in hafnium metal

Journal Article · Sat Jun 21 00:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4884436· OSTI ID:22303993

Sharma, Surinder M. ^[1]; Gyanchandani, Jyoti; Dey, G. K. ^[2]; Somayazulu, M. ^[3]; Sikka, S. K. ^[4]

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1. High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085 (India)
2. Materials Science Division, Bhabha Atomic Research Centre, Mumbai-400 085 (India)
3. Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015 (United States)
4. Indian National Science Academy, New Delhi-110 002 (India)

There has been a recent controversy about the high pressure polymorphism of Hafnium (Hf). Unlike, the earlier known α→ω structural transition at 38 ± 8 GPa, at ambient temperature, Hrubiak et al. [J. Appl. Phys. 111, 112612 (2012)] did not observe it till 51 GPa. They observed this transition only at elevated temperatures. We have reinvestigated the room temperature phase diagram of Hf, employing x-ray diffraction (XRD) and DFT based first principles calculations. Experimental investigations have been carried out on several pure and impure Hf samples and also with different pressure transmitting media. Besides demonstrating the significant role of impurity levels on the high pressure phase diagram of Hf, our studies re-establish room temperature α→ω transition at high pressures, even in quasi-hydrostatic environment. We observed this transition in pure Hf with equilibrium transition pressure P{sub o} = 44.5 GPa; however, with large hysteresis. The structural sequence, transition pressures, the lattice parameters, the c/a ratio and its variation with compression for the α and ω phases as predicted by our ab-initio scalar relativistic (SR) calculations are found to be in good agreement with our experimental results of pure Hf.

• OSTI ID: 22303993
• Journal Information: Journal of Applied Physics, Vol. 115, Issue 23; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AMBIENT TEMPERATURE
COMPRESSION
COMPUTERIZED SIMULATION
DENSITY FUNCTIONAL METHOD
EQUILIBRIUM
HAFNIUM
HYSTERESIS
LATTICE PARAMETERS
PHASE DIAGRAMS
PRESSURE RANGE GIGA PA
RELATIVISTIC RANGE
TEMPERATURE RANGE 0273-0400 K
X-RAY DIFFRACTION