Polyamorphism of a Ce-based bulk metallic glass by high-pressure and high-temperature density measurements

International audienceMetallic glasses are of recent interest worldwide due to their remarkable physicochemical properties which canbe put in relation with their crystalline counterparts. Among them, cerium-based metallic glasses (Ce-MGs) haveunique features such as the existence of polyamorphism under pressure, which is unexpected in these spatiallycompact systems. While a phase transition between amorphous phases with change of density and local structurehas been previously detected, the corresponding structural variation under pressure was not clearly identified dueto difficulties in performing accurate measurements and reliable analysis. In this work, angle dispersive x-raydiffraction experiments of Ce69Al10Cu20Co1 bulk metallic glass have been performed up to 16 GPa along twodistinct isotherms (300 and 340 K). All of the diffuse signals have then been processed in order to extract the structurefactor S(Q), the pair distribution g(r), the atomic density ρ, and the compressibility as a function of pressureand temperature. These are crucial probes to fully characterize the phase diagram, and they clearly confirm theexistence of a link between polyamorphism in Ce-MGs and the γ α transition in pure cerium. Finally, owingto the presence of a critical point in pure solid Ce, the existence of such a feature is discussed here for Ce-MGs