Polyamorphic transitions in Ce-based metallic glasses by synchrotron radiation

Abstract

We report here on a polyamorphic-phase transition upon application of pressure on a Ce-based metallic glass, Ce${}_{70}$Al${}_{10}$Ni${}_{10}$Cu${}_{10}$, investigated by x-ray diffraction and inelastic x-ray scattering. This alloy is found to display a strong hysteresis in volume per atom upon application and subsequent release of pressure. The observed structural changes are correlated with changes observed by inelastic x-ray scattering in the elastic constants, acoustic mode frequencies, and sound speed. The results reported here point toward three different amorphous phases for this alloy existing in the 0--25 GPa pressure region: low- and high-density states and an intermediate mixed state that displays a hysteresis behavior. Finally, we discuss the impact of Ce concentration on the polyamorphic transition for a series of Ce-based metallic glass alloys and link it to the phase transformation between $\ensuremath{\gamma}$-Ce and $\ensuremath{\alpha}$-Ce under pressure.