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

作者：Endo Naruki^*; Saitoh Hiroyuki; Machida Akihiko; Katayama Yoshinori; Aoki Katsutoshi

来源：Journal of Alloys and Compounds, 2013, 546: 270-274.

DOI：10.1016/j.jallcom.2012.08.083

• TiH2
• Phase diagram
• Equation of state
• High pressure and high temperature
• In situ X-ray diffraction measurement

We determined the phase diagram and the equation of state (EoS) of TiH2 at high pressures up to 8.7 GPa and high temperatures up to 600 degrees 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 degrees 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 degrees 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 angstrom(3), temperature derivative of the bulk modulus at constant pressure (partial derivative K/partial derivative T)(P) = -0.01 +/- 0.02, and volumetric thermal expansivity alpha = alpha + bT with alpha = 2.62 +/- 1.4 x 10 (5) and b = 5.5 +/- 4.5 x 10 (8). K-0 of fcc TiH2 was close to those for pure Ti and bct TiH2 reported in previous studies.

• 出版日期2013-1-5