Accurate Equation of State of AlPdMn up to 35 GPa and Pressure Effect on the Frozen-In Phason Strain

Abstract

Angle-dispersive monochromatic x-ray diffraction spectra from a perfect single-grain AlPdMn quasicrystal have been obtained under hydrostatic pressure in a diamond anvil cell up to 35 GPa. More than 50 Bragg peaks with sharpness comparable to that at ambient conditions were observed up to the maximum pressure, indexed and used to measure the hypercubic 6D lattice parameter, providing the most accurate determination of the equation of state in this pressure range to date. Within the instrumental resolution, the absence of broadening of the diffraction peaks indicates the absence of structural transition and/or unusual configurational entropy change expected from previous studies through pressure-induced amorphization or phason defects.

Optical Spectroscopy Methods and High‐Pressure–High‐Temperature Studies

“…The transit time is measured under pressure with the same accuracy. The pressure dependence of the thickness is obtained from the equation of state [87], and the sound velocity finally deduced as a function of pressure.…”

Sound Velocity and Absorption Measurements under High Pressure Using Picosecond Ultrasonics in a Diamond Anvil Cell: Application to the Stability Study of AlPdMn

“…The detection is carried out by a stabilized Michelson interferometer which allows the determination of the reflectivity imaginary part change [11] (at high pressure, interferometric measurements are necessary to efficiently detect acoustic pulses with a low frequency spectrum due to sound attenuation). Extracted from a large single quasicrystal of icosahedral Al 68:2 Pd 22:8 Mn 9 [ 5:081 g:cm ÿ3 ] [12] previously used to determine accurate equation of state from both ultrasonics and x-ray diffraction techniques [13], a thin platelet with surface of about 30 30 m 2 was loaded into the experimental volume of a DAC. Two experimental runs have been carried out with sample embedded in different PTM [14], neon, and argon (see Fig.…”

“…We systematically observed a small amount of rare gas (thickness of about 1 m) between the anvil and the pump-side AlPdMn surface. Using the well-known acoustic velocity of AlPdMn at ambient conditions [13], the thickness of the single-grain platelet was measured to be 9:121 m from picosecond measurement (using the same setup as previously described). Pressure was measured using the fluorescence emission of a 5 m ruby sphere [15] placed close to the sample in the gasket hole.…”

“…This is in agreement with Duquesne [23] who has demonstrated that the thermoelastic contribution to the process of sound absorption in AlPdMn is negligible in the GHz range with respect to the viscosity of the phonons gas (100 K < T < 300 K). Lattice contraction effect on the sound absorption could thus be interpreted through a peculiar Akhieser con- [13]. Black crosses: picosecond data from the first run using argon as PTM.…”

“…For AlPdMn, the longitudinal velocity v L has been determined using the following equation: v L = 2d/∆t , where ∆t is the time interval between the two adjacent acoustic echoes and d the thickness of the sample deduced at high pressure from its initial value and the pressure dependence of the bulk modulus B [13]. The transversal sound velocity v T is finally extracted from the same equation of state and the definition of the bulk modulus for acoustically isotropic materials: B = ρ(v 2 L − 4/3v 2 T ).…”