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Phase diagram and equation of state of TiH2 at high pressures and high temperatures

Authors :
Hiroyuki Saitoh
Yoshinori Katayama
Katsutoshi Aoki
Akihiko Machida
Naruki Endo
Source :
Journal of Alloys and Compounds. 546:270-274
Publication Year :
2013
Publisher :
Elsevier BV, 2013.

Abstract

We determined the phase diagram and the equation of state (EoS) of TiH 2 at high pressures up to 8.7 GPa and high temperatures up to 600 °C by in situ synchrotron radiation X-ray diffraction measurements. Compression induced strain inhibited the phase transition from the low-temperature bct phase to the high-temperature fcc phase, making the phase diagram difficult to determine. However, heating around 600 °C relieved the strain, and the phase boundary between the bct and fcc phases was elucidated. The phase transition temperature at ambient pressure increased from around room temperature to 200 °C at 8.7 GPa. The high temperature Birch–Murnaghan EoS was determined for the fcc phase. With the pressure derivative of the bulk modulus K ′ 0 = 4.0, the following parameters were obtained: ambient bulk modulus K 0 = 97.7 ± 0.2 GPa, ambient unit cell of the fcc phase V 0 = 88.57 ± 0.02 A 3 , temperature derivative of the bulk modulus at constant pressure (∂ K /∂ T ) P = −0.01 ± 0.02, and volumetric thermal expansivity α = a + bT with a = 2.62 ± 1.4 × 10 −5 and b = 5.5 ± 4.5 × 10 −8 . K 0 of fcc TiH 2 was close to those for pure Ti and bct TiH 2 reported in previous studies.

Details

ISSN :
09258388
Volume :
546
Database :
OpenAIRE
Journal :
Journal of Alloys and Compounds
Accession number :
edsair.doi...........01a442018833140928c9a00634994403
Full Text :
https://doi.org/10.1016/j.jallcom.2012.08.083