Variations of lattice constants and thermal expansion coefficients of indium at high pressure and high temperature

The effects of pressure and temperature on the lattice constants and thermal expansion coefficients of Indium were studied up to 18.6 GPa and 506 K based on in situ X-ray diffraction method with an externally heated diamond anvil cell. The results show that the measured axial ratio (c/a) decreases with increasing temperature and its temperature dependence decreases with increasing pressure. The thermal expansion coefficient of the a-axis decreases with increasing pressure up to 7 GPa and remains almost constant above 7 GPa, whereas that of the c-axis increases monotonously with pressure and changes from negative to positive at around 7 GPa. The observed behavior suggests that temperature reduces the tetragonal distortion on the lattice, and its effect is dominant below 7 GPa; in contrast, pressure enhances lattice distortion, and tends to have a stronger effect above 7 GPa.